Recovery, GH pulses and the CJC / ipamorelin pair

Two on-switches sit on one secretory cell in the pituitary — not a night's slow-wave sleep freeze-dried, and not the licensed somatropin pen a clinic already writes. The cell is a somatotroph, the growth-hormone factory that makes up half or more of the anterior pituitary in a young adult. It stores the 191-residue four-helix bundle in dense-core granules and waits for a ratio in portal blood. Growth-hormone-releasing hormone, GHRH, occupies a class-B receptor and loads Gs, the stimulatory G protein that raises cyclic AMP. The ghrelin receptor, GHS-R1a, occupies a class-A receptor and loads Gq, which lifts calcium. Cyril Bowers showed, decades ago, that turning both locks at once releases more growth hormone than you'd get by adding the two results together. CJC without DAC is a tetrasubstituted GRF(1–29) that still pulses at the first lock. Ipamorelin is a selective pentapeptide at the second, built so ACTH and prolactin mostly stay out of the table. The blend is ten milligrams of each, freeze-dried together, because the papers already treat the pair as cooperative. The largest native pulse still fires in slow-wave sleep.

In short. Two pituitary switches release growth hormone. One copies a brain peptide in bursts. The other is a clean ghrelin-receptor key. Together they beat either alone.

Let's put the chemistry on the table before we hang a caption on it. CJC without DAC is modified GRF(1–29): typically D-Ala2, Gln8, Ala15 and Leu27 on the amidated first twenty-nine residues of hypothalamic GHRH, no N-ε-maleimidopropionyl-lysine, no albumin glue, a plasma window measured in tens of minutes rather than days. Native GHRH is forty-four residues; the truncation already occupies GHRHR with full efficacy. Dipeptidyl peptidase-IV, DPP-IV, would otherwise cleave the Ala2–Asp3 bond in minutes and abolish agonism — the same enzyme that chews native GLP-1. Ipamorelin is Aib-His-D-2-Nal-D-Phe-Lys-NH2, five residues, a C-terminal amide, molecular weight 711.9, CAS 170851-70-4, the sequence Raun, Hansen, Nielsen, Heinig, Andersen, Thøgersen, Ankersen and Madsen put into the European Journal of Endocrinology in 1998. Recombinant somatropin is a different listing: the 191-residue ligand itself, occupying the growth-hormone receptor on liver and bone, skipping the somatotroph entirely. Three carbon skeletons. Three receptors. A forum caption will tell you they are one recovery stack. A chromatogram will tell you they are three molecules, and the chromatogram is the better witness if you actually want to know what you reconstituted.

In short. CJC without DAC is a short, enzyme-resistant copy of the brain's go peptide. Ipamorelin is a five-amino-acid ghrelin-receptor key. Injected growth hormone is a third molecule.

Recovery is a clinic word and a gym word before it is a receptor, and that's fine — words get borrowed. In sport it means the hours after load when glycogen is restocked, connective tissue is asked to align, and a person is allowed to sleep. In endocrinology it is not a synonym for those hours. It is a search habit that landed on the growth-hormone axis because GH pulses, IGF-1, and slow-wave sleep already sit in the same night, and because forums bundled a GHRH analogue with a secretagogue and called the pair a recovery stack. Johannes Veldhuis spent a career showing that the axis writes a digital signal: discrete nocturnal bursts, a low interpulse baseline, suppression by hyperglycaemia, amplification by fasting. A secretagogue literature does not replace that night, and we shouldn't ask it to. The sequences are real chemistry. The pulses are real physiology. They don't become a training plan because a search bar put them on the same afternoon. Our job here is to keep the chemistry and the night in the same picture without pretending they're the same object. That's a kindness to you, and to the axis.

In short. Recovery in sport is rest, food and sleep. The hormone axis this page maps is a separate object: night bursts of growth hormone, not a training plan.

What we'll walk through together is the two-input machine, the two G proteins, the reason Bowers' pair is super-additive, the Veldhuis pulse, the slow-wave window nobody gets to skip, the analogue that still troughs, the pentapeptide that left the ACTH circus off, the twenty-milligram pair as logistics, and the 191-mer that lives on a different shelf. Physiotherapy, a sleep study, and a deficiency work-up live in other rooms, and they should. Tesamorelin is the licensed GHRH analogue in a named indication. Recombinant somatropin remains a medicine on an endocrine ward. These listings are characterised lyophilised sequences for the assays you can already name: a pituitary-slice GH release, a two-receptor synergy experiment, a frequent-sampling curve that can see a burst. The neighbouring essays take each microphone in turn — modified GRF(1–29) without the maleimide, ipamorelin at Cell length, the whole axis, the 191-mer, the sleep-and-glucose night. This page is the tissue-and-search page they share. A characterised cake is a reagent. A night of slow-wave sleep is still a night, and it's still the most interesting experiment in the room.

In short. We'll map two receptors, two analogues, a pair, and the sleep window the native pulse still owns. That's physiology, not a protocol.

People type recovery into a peptide shop because the word is doing three jobs at once, and the internet never quite split them. Soft-tissue recovery is a tendon, a muscle, a loading programme, the BPC-157 and TB-500 neighbourhood already written next door. Metabolic recovery is glycogen, fluid, a meal with leucine in it. Endocrine recovery, in the sentence this page is allowed to own, is whether the somatotroph still fired a decent nocturnal burst and whether the liver wrote IGF-1, the acid-labile subunit and IGFBP-3 in response. Those are different jobs, and you're allowed to care about all three. A person who cannot train on Tuesday may have a painful Achilles, a calorie deficit, a short night, or a flattened GH series, and the search bar will offer the same two lyophilised cakes for all four. Name the object and the rest of the map gets easier. If the object is a cable, the tendon essay is next door. If the object is a scored night, the sleep-architecture essay is next door. If the object is two G proteins on a granule, stay here. We'll take our time with that granule. It's worth it.

In short. The word recovery hides several problems: a sore tendon, empty fuel stores, a short night, or a quiet hormone pulse. This page is only the last of those.

Licensed growth-hormone medicine already exists, and we should keep that in view so a pair of analogues isn't mistaken for it. Recombinant somatropin is a daily subcutaneous replacement in children with proven GH deficiency and in adults who meet a stimulation-test threshold; it is one of the cleaner endocrine success stories of the late twentieth century, and it earned that reputation in clinic, not in a forum. Pegvisomant occupies the GH receptor as an antagonist in acromegaly. Tesamorelin, a trans-3-hexenoyl GRF(1–44), is licensed in the United States as Egrifta for reduction of excess abdominal fat in HIV-associated lipodystrophy. Those objects have indications, pharmacovigilance, and a fridge that is not this one. Modified GRF(1–29) without DAC and ipamorelin are named sequences with pituitary-slice and animal papers. Keep the jobs apart and you can love both literatures. A person who thinks they have GH deficiency is a clinic object, with an IGF-1, an insulin-tolerance or glucagon stimulation test, and a pituitary MRI when the biochemistry says so. A pair of research cakes is not that work-up, and it doesn't need to be. It's a different question, asked of a different fridge.

In short. Real growth-hormone medicines already exist for proven deficiency and for one named fat-distribution problem. The two research peptides on this page are not those medicines.

The gym origin story and the endocrine origin story are the same two molecules wearing two hats, which is how folklore gets written, and folklore is allowed to be wrong without being stupid. A nocturnal GH burst is larger in slow-wave sleep, and slow-wave sleep is what a hard training block is supposed to earn. IGF-1 talks to muscle and bone. Fasting and ghrelin amplify the axis; abdominal adiposity and hyperglycaemia suppress it. None of that makes a GHRH analogue a recovery drink, and none of it makes the physiology imaginary. The physiology is real and older than either vial. Van Cauter, Spiegel and Leproult wrecked next-morning glucose in healthy young men by taking the night apart, and the GH peak shrank with the slow waves. That's an architecture finding, and it's one of the more useful rude sentences in endocrinology. It's also why this page will keep sending you back to a dark room before it sends you to a reconstitution kit. The peptides sit on named receptors. The night sits on named stages. Confusing those two floors is how a serious axis becomes a caption. We'll keep the floors.

In short. Hard training and deep sleep both sit near growth-hormone bursts. That neighbourhood is real. It does not turn a receptor ligand into a recovery drink.

We're not going to flatten those floors into a stack caption, because the receptors won't let us. Soft-tissue peptides, copper tripeptides, mitochondrial 16-mers and a weekly incretin all live on the same shelf and all get filed under feeling better. GHRHR is a class-B GPCR on a somatotroph. GHS-R1a is a class-A GPCR on a somatotroph, on arcuate NPY neurons, and on vagal afferents. Somatropin occupies GHR, a class-I cytokine receptor, on hepatocytes. Those three occupancies are three experiments, and a reading list can sit them together without mixing the wells. If you reconstitute them into one syringe and report a waist, you can't tell which peak you earned. Attribution is the job, and it's a more interesting job than a stack. The rest of this page is the two on-switches, named at every floor, with the papers a pituitary bench is expected to cite, and with the sleep window left on the diagram because leaving it off would be the brochure version of the same axis. The brochure is shorter. The axis is better.

In short. Different peptides on the same shelf ask different receptors. This page keeps the two growth-hormone switches separate from the rest of that neighbourhood.

The somatotroph is the machine, and it's a rather wonderful one. It is electrically excitable. It fires action potentials. It packs mature 22-kilodalton growth hormone into dense-core granules, a four-helix bundle held by disulphides, the same structural neighbourhood as prolactin and erythropoietin. A 20-kilodalton splice variant that lacks residues 32–46 is a minority of circulating GH and a reason some assays under-count, which is a small, irritating, true fact. Synthesis is a slower clock: GHRH tone, via cyclic AMP and CREB and Pit-1, writes more GH gene product and restocks the readily-releasable pool over hours. Exocytosis is a faster clock: local calcium at the granule, seconds to minutes, fusion, a pulse in portal and then peripheral blood. Two clocks, one cell. A short-acting analogue asks the first of those clocks as a fusion event and the second only if exposure lasts. An albumin-conjugated analogue asks both, and then asks what the liver does with a flattened GH tone, which is a third question. The cell does not read captions. It reads cyclic AMP, a calcium current, a Gi brake, and how many granules are waiting. That's a more interesting sentence than a stack, once you sit with it.

In short. Pituitary growth-hormone cells store the hormone in granules and dump them when calcium rises. Making more hormone is a slower job than releasing what is already packed.

GHRH is the first on-switch, and it is hypothalamic. The neurons sit mainly in the arcuate nucleus. Their axons end on the portal plexus a millimetre or two from the anterior pituitary — a tiny, privileged postcode. The peptide is forty-four residues in the human, processed from a larger precursor, amidated at the C-terminus. Guillemin's group and Vale and Rivier's group isolated it in 1982 from tumour and hypothalamic extracts after a decade of false starts; Science and Nature, the same year, a sequence you could synthesise. That's one of those years you wish you'd been in the room. The first twenty-nine residues, GRF(1–29)-NH2, already occupy GHRHR with full efficacy. The C-terminal fifteen contribute to binding and to circulating half-life in some assays; they are not required for the activating job. Portal concentrations are high, pulsatile, and largely cleared before they reach a cubital vein. A peripheral GHRH measurement is therefore a poor photograph of what the somatotroph just heard. A laboratory analogue arriving from the periphery occupies one receptor in that village. The village is still there when the analogue arrives, and it still has a vote.

In short. GHRH is a 44-amino-acid brain peptide that tells the pituitary to release growth hormone. The first 29 amino acids already do the full job at the receptor.

The second on-switch is not hypothalamic in origin for most of its circulating mass, which is part of why it took so long to find. Kojima, Hosoda, Date, Nakazato, Matsuo and Kangawa, Nature 1999, 402: 656–660, found ghrelin: a twenty-eight-residue peptide from the stomach, uniquely octanoylated on serine 3 by ghrelin O-acyltransferase. The acylation is obligatory for GHS-R1a agonism — a fat chain on one serine, without which the lock doesn't turn. Des-acyl ghrelin circulates in larger amounts and is a different conversation. Howard, Smith and colleagues had cloned the receptor three years earlier as an orphan, Science 1996, a class-A GPCR in pituitary and hypothalamus that functions in growth-hormone release. At the somatotroph, GHS-R1a synergises with GHRH. In the arcuate, the same receptor sits on NPY/AgRP neurons and is the reason ghrelin is an orexigenic signal as well as a secretagogue. Vagal afferents carry a third copy of the story. One ligand, several addresses, one G protein family. A catalogue pentapeptide that occupies GHS-R1a will inherit that geography whether a recovery caption wants it to or not, and geography is information, not a nuisance.

In short. Ghrelin is a stomach hormone with a fat chain on one serine. The same receptor that raises growth hormone also sits on hunger circuits and gut nerves.

Somatostatin is the off-switch, and if we add two on-ligands without naming it we've described two-thirds of the hypothalamic sentence. Brazeau, Vale, Guillemin, Science 1973: a fourteen-residue cyclic peptide from hypothalamic extracts that inhibited growth-hormone release in pituitary cells, named for that job before its wider life as a gut and pancreatic hormone was mapped. A twenty-eight-residue N-terminally extended form exists and is not a footnote in some tissues. On the somatotroph the relevant receptors are mainly SSTR2 and SSTR5, class-A GPCRs coupled to Gi. Adenylyl cyclase falls. Cyclic AMP falls. The L-type calcium current that GHRH had opened is opposed. Granule fusion slows. Somatostatin tone is high between pulses and drops as a pulse is allowed through. The go is therefore a triple event: GHRH up, ghrelin tone present, somatostatin down, arriving as a ratio. An analogue at GHRHR or at GHS-R1a still has to live with that ratio. It cannot repeal Gi. Arginine, in clinical GHRH tests, is there in part to suppress somatostatin, which is a rather elegant piece of clinical cunning. Name the stop if you claim a pulse. The stop is half the beauty of the axis.

In short. Somatostatin is the brain's stop signal for growth hormone. A pulse is a ratio of two on-switches to that off-switch, not a button.

Genetic proofs keep the cascade in order, which is why they belong on a recovery page and not only in a textbook. The little mouse carries a missense mutation in Ghrhr; it is GH-deficient and small, and it is why Mayo's 1992 clone of the receptor was more than a sequence on a gel. Human isolated GH deficiency type IB includes GHRHR mutations, particularly in consanguineous cohorts that paediatric endocrinology still cites. Laron syndrome is the next floor down: GHR mutations, high GH, very low IGF-1, a receptor that will not rotate and will not recruit JAK2. A GHRH analogue cannot rescue Laron. A secretagogue cannot rescue a missing STAT5b. Mecasermin, recombinant native IGF-1, is the licensed ligand when the cascade is broken below GHR, in a named paediatric indication. Catalogue modified GRF(1–29) and catalogue ipamorelin are not rescues for a floor they never meet, and they don't claim to be. Occupying GHRHR or GHS-R1a is a precise question. It's a useless question if the somatotroph, or the GH receptor, or STAT5b, is the floor that actually failed. The genetics are here so the microphone stays labelled. Labelled microphones are how you design an experiment you can actually interpret.

In short. Mutations show the cascade is ordered: this receptor, then growth hormone, then IGF-1. An analogue cannot fix a break at a floor it never reaches.

Portal blood is the medium, and it is not a sample from the arm. Concentrations in the long portal vessels are high, pulsatile, and largely cleared before they reach a cubital vein. Clinical tests that still use GHRH, often with arginine to suppress somatostatin, are provocations: they ask whether the pituitary can still answer, not what the hypothalamus whispered an hour ago. The arcuate GHRH neuron is itself gated. Slow-wave sleep is the largest physiological window. Fasting amplifies. Sex steroids shape amplitude and frequency. Thyroid hormone is permissive for GH synthesis; a hypothyroid somatotroph writes fewer granules. Glucocorticoids in excess suppress the axis at hypothalamus and pituitary. Free fatty acids suppress GH release, one of the reasons obesity is a low-GH state. Hyperglycaemia will blunt a GHRH or secretagogue challenge, which is why a fed animal and a fasted animal are not the same assay. The somatotroph is a cell reading a hypothalamic ratio, a metabolic plasma, and a sleep clock. Two laboratory analogues occupy two receptors in that village. The village still votes, and that's not a problem. That's the physiology.

In short. The pituitary hears these signals in a local blood supply, gated by sleep, sugar, fat and other hormones. An analogue occupies one receptor; the rest of the body still has a vote.

GHRHR is a class-B secretin-family GPCR, the same structural neighbourhood as GLP-1R, GIPR, GCGR and the secretin receptor itself. Seven transmembrane helices, a large N-terminal extracellular domain that captures the C-terminal half of the peptide, and a transmembrane pocket that reads the N-terminus. Occupancy rearranges the helices. The intracellular face becomes a guanine-nucleotide exchange factor for Gs. Mayo cloned the receptor in the early 1990s; Molecular Endocrinology, 1992. Gs is the first amplifier. GTP-bound Gαs occupies adenylyl cyclase. Cyclic AMP rises, in somatotrophs, by enough to occupy protein kinase A. PKA phosphorylates CREB, which is the transcriptional half of a longer GHRH exposure, and phosphorylates the machinery that opens L-type voltage-gated calcium channels. Calcium enters. Local calcium at the granule is the proximate trigger for exocytosis of stored growth hormone. Cyclic AMP is hydrolysed by phosphodiesterases. Somatostatin, via Gi, opposes the cyclase. The pulse is therefore a contest at the cyclase as well as a contest at the portal. Two contests, one granule. That's a lot of information packed into a cell you could hide under a fingernail.

In short. The GHRH receptor is a seven-helix protein that loads a stimulatory G protein called Gs. That raises cAMP, opens calcium channels, and dumps stored growth hormone.

GHS-R1a is a class-A GPCR, rhodopsin-like, a peptide-binding pocket among the helices rather than a large hormone-catching ectodomain. Occupancy rearranges the helices. The intracellular face becomes a guanine-nucleotide exchange factor, predominantly for Gq/11. Gq is the first amplifier. GTP-bound Gαq occupies phospholipase C-β. PIP2 is cleaved to IP3 and diacylglycerol. IP3 opens IP3-gated channels on the endoplasmic reticulum. Calcium rises from stores. Diacylglycerol occupies protein kinase C. The calcium rise, in a somatotroph, is the proximate co-trigger for exocytosis, and it also depolarises the cell so that Cav1 channels open and add a plasma-membrane calcium current on top of the store release. A Gi component is real and is part of why the electrophysiology of a somatotroph seeing ghrelin is not a carbon copy of one seeing GHRH. Lefkowitz and Kobilka's chemistry Nobel in 2012 was for this family. Ligand stays outside. Information crosses as conformation. Amplification is enzymatic. Five residues can fill a class-A pocket. They cannot mimic a class-B ectodomain ligand, and they don't need to. Two locks. Two shapes. One granule if both turn.

In short. The ghrelin receptor is a different seven-helix protein. It raises calcium from internal stores and through membrane channels, using a G protein called Gq.

L-type calcium current is the sentence most recovery copy skips, and it's the sentence that makes the synergy make sense. Somatotrophs fire action potentials. The depolarisation that GHRH and ghrelin both encourage, by different G proteins, opens Cav1 channels. The calcium that enters is the fusion signal. Block those channels with a dihydropyridine in a pituitary slice and the GH pulse collapses, which is old pharmacology and still a useful control if someone claims a pair of analogues released hormone by a novel inner path. GHRH gets there through cAMP and PKA. Ghrelin gets there through Gq, phospholipase C, IP3, and a rise in intracellular calcium that also depolarises. The two paths converge on the same granule. That convergence is why co-application of a GHRH analogue and a GHS-R1a agonist releases more GH than either ligand alone, in slices and in animals, and why textbooks draw the large pulses as a combination. Synergy is a G-protein fact. Isolating each ligand is how you know which receptor did the work. Naming both concentrations is the standard the pituitary-slice papers already set, and it's a standard worth keeping because the granule is worth keeping honest.

In short. Both switches raise calcium inside the pituitary cell, by different routes, and growth-hormone granules then fuse. Together they make the large bursts.

Bowers showed the pair is more than additive, and that sentence is the intellectual reason a catalogue freeze-dries the two analogues together at all. Give GHRH alone and you get a pulse. Give a secretagogue alone and you get a pulse that still wants GHRH tone in the background; in hypothalamic–pituitary clamp experiments, a secretagogue in the absence of GHRH produces a smaller burst than the pair. Give both, and the output is super-additive because the second messengers are. Cyclic AMP and calcium converge on the fusion machinery. The large nocturnal pulses that Veldhuis deconvolved are, on this picture, a GHRH event amplified by ghrelin tone and permitted by a somatostatin trough. Two receptors, two G proteins, one granule. Combined without naming both concentrations, the pair becomes a stack, and a stack is a purchasing habit rather than an experiment. The papers that combined GHRH and a secretagogue in pituitary slices named both receptors and both doses. That's the standard, and it's a friendly one: it lets you see the extra. Partner is a dangerous word if it hides the two locks. Two sequences. Two locks. The extra is the point.

In short. A GHRH analogue plus a ghrelin-receptor key releases more growth hormone than adding the two results together. That extra is why the pair exists in the papers.

Desensitisation is why more ligand is not more signal forever, and it is one of the costs an albumin-conjugated analogue buys when it buys duration. Occupied GHRHR is phosphorylated by GRKs, binds β-arrestin, and is internalised. Occupied GHS-R1a does the same arithmetic on a class-A body. Recycle or degrade, depending on the duration and the cell. A somatotroph that sees continuous GHRH tone will, within hours, present fewer receptors and a smaller cAMP increment per molecule of ligand. That's ordinary GPCR biology, the same arithmetic Lefkowitz spent a career on, applied to receptors whose ligands in life are pulses. A research analogue without DAC was built for the other trade: occupy, raise cAMP or calcium, fuse granules, and then get out of the way so the receptor census and the trough can recover. Ipamorelin was not built to last a week either. Getting out of the way is a pharmacokinetic property. It is also a scientific decision, and a rather elegant one. Continuous application in a well is a different experiment from a bolus, and both are different from a nocturnal endogenous wave. Name which clock you meant. The cell will notice even if a caption doesn't.

In short. If either receptor stays occupied for too long, it is pulled inside and the cell hears less. Short analogues leave so hearing can recover.

Constitutive activity is a property GHS-R1a is famous for, and a property we have to keep honest when a recovery caption treats the pentapeptide as a simple volume knob. GHS-R1a signals a bit without ligand. Inverse agonists exist in the literature because of that basal tone. The physiological argument is that a constitutively noisy secretagogue receptor sets a floor under somatotroph excitability and under arcuate NPY tone, and that acylated ghrelin then turns the volume further up. Whether a given analogue is a full agonist, a partial agonist, or something with inverse-agonist neighbourhood on some readouts is a concentration-and-assay question, not a caption. Raun's tables treated ipamorelin as an agonist that released GH. They did not claim to have quieted basal GHS-R1a. If your blot is about constitutive activity, this pentapeptide is probably the wrong tool. If your blot is about raising GH from a Gq-coupled occupancy without an ACTH confound, it is the right one. GHRHR does not carry the same constitutive-activity folklore. Two locks. Two personalities. One granule downstream if both turn, and the personalities are part of why the pair is interesting rather than merely additive.

In short. The ghrelin receptor leaks a little signal even before a ligand arrives. Ipamorelin turns the volume up. It was not built to silence that leak.

Johannes Veldhuis spent a career showing that growth hormone is a digital signal, and once you've seen his deconvolutions you can't unsee them. Frequent-sampled plasma GH, in humans and in animals, yields discrete bursts superimposed on a low interpulse baseline. Most of the mass is in the bursts. Most of the bursts, in a healthy adult, cluster after sleep onset, in slow-wave sleep, with a smaller daytime population. Amplitude falls with age, with abdominal adiposity, with hyperglycaemia. Amplitude rises with fasting, with oestradiol in some protocols, with a GHRH or secretagogue challenge. The pattern is the message. A single morning clinic GH is almost uninterpretable without an IGF-1, and even IGF-1 is an integral, not a pulse photograph. The papers sit in Journal of Clinical Endocrinology and Metabolism, in Endocrine Reviews, in a run of American Journal of Physiology pieces that a generation of fellows were handed. If you report GH as a continuous infusion or as a daily subcutaneous bolus and then talk as if you'd reproduced physiology, you haven't read Veldhuis yet, and he's a pleasure to read. These analogues exist so that reading still has reagents.

In short. Growth hormone comes in bursts, mostly at night. Veldhuis showed the pattern itself carries the message. A flattened dose is a different signal from a pulse.

Sampling is the unglamorous half of pulsatility, and it is where analogue papers most often cheat, usually without meaning to. A single clinic GH, drawn at nine in the morning, reports a trough more often than a peak and cannot distinguish deficiency from a nadir between bursts. Frequent sampling, every ten or twenty minutes overnight, is how Veldhuis deconvolved mass and frequency; it is also how you prove you've reproduced a pulse rather than a smear. IGF-1 is the integral: a hepatic average over hours, useful, and blind to whether the night was three large bursts or a flattened plateau. IGFBP-3 and the acid-labile subunit are slower integrals still. Occupy GHRHR with a thirty-minute analogue, or GHS-R1a with a pentapeptide, and then draw IGF-1 at a week, and you have measured the liver's running mean, not the somatotroph's burst. Draw GH at twenty-minute intervals around the dose if the question is the pulse. Draw IGF-1 if the question is the hepatic programme. Name which integral you meant. The two numbers don't substitute for each other, and they don't need to. They're two photographs of two clocks, and both clocks are real.

In short. One morning blood test for growth hormone is usually a quiet gap. Frequent samples show bursts. IGF-1 averages hours of liver output and hides those bursts.

Continuous growth hormone is not pulsatile growth hormone at the liver, and the liver is a careful reader. Hepatocytes reading a pulsatile STAT5b phosphorylation write IGF1, ALS and IGFBP3, the ternary-complex programme that circulating IGF-1 actually travels in. Hepatocytes reading a flattened GH tone write a different programme: more insulin antagonism, a different lipid-gene set, less of the IGF pattern many protocols thought they wanted. Receptor down-regulation contributes. SOCS2, a STAT5b target, feeds back and shuts the receptor down when occupancy is unrelieved. Jørgensen, the older rodent infusion studies, and the clinical experience with continuous subcutaneous GH pumps all point the same way. In the rat, a three-hour GH infusion and a pair of pulses matched for area-under-the-curve do not write the same cytochrome P450 genes. Pattern is information. Flatten it and you have changed the ligand even if the amino-acid sequence of GH is identical. That sentence is the design constraint for every GHRH analogue, and it is why this catalogue stocks CJC without the Drug Affinity Complex rather than the albumin conjugate. The trough is not wasted time. The trough is part of the sentence.

In short. The liver reads growth-hormone bursts as one gene programme and a continuous drip as another. Flatten the pulse and you change the message.

Sexual dimorphism of the pulse is not a footnote, and it is another reason a week-long analogue and a pulse-length analogue are two questions. Male rodents fire large, regular nocturnal GH bursts against a near-silent baseline. Female rodents run a more nearly continuous, lower-amplitude tone. The liver reads those two patterns as two programmes. A classic molecular signature: male-pattern GH, in the rat, induces some cytochrome P450 genes (CYP2C11) and suppresses others (CYP2C12); female-pattern GH does the reverse. STAT5b pulsing versus STAT5b occupancy that never quite returns to baseline is a large part of the mechanism. Knock out STAT5b and the male-specific liver programme collapses toward female. Waxman, Norstedt, Mode and others built that literature, and it's one of the prettier stories in endocrine biochemistry. Humans are less cartoonishly dimorphic than rats, but the principle survives: women have more frequent, smaller pulses and a higher interpulse baseline; men have larger, less frequent bursts. A pulse-length pair can in principle respect that dimorphism. An albumin-conjugated GHRH analogue cannot, because it has already chosen the never-quite-baseline tone as its pharmacokinetic fate. The fate is a design choice. Name it.

In short. Males and females fire growth hormone in different patterns, and the liver reads those patterns as different genes. A week-long analogue erases that difference.

Slow-wave sleep is the largest physiological gate, and a recovery page that skips it has already become a brochure. The largest GHRH-driven pulses coincide with N3, the high-amplitude delta stage concentrated in the first two cycles of a young-adult night. Deprive the slow waves and the GH peak shrinks. That's why night-time sampling exists, and why a daytime secretagogue challenge is a different probe from a nocturnal endogenous pulse. Spiegel, Leproult and Van Cauter's sleep-restriction work in healthy young men is the rude version of that sentence: take the architecture apart and next-morning glucose handling suffers, and the GH integral is one of the endocrine casualties. Adenosine is the local metabolite most often named as slow-wave debt's coin. Caffeine is an adenosine-receptor antagonist, which is why an espresso at four in the afternoon is an architecture experiment whether or not anyone scored it. A pair of analogues occupies two receptors. The stage that permits the native burst is still a scored EEG night. Missing that night and expecting a pentapeptide to stand in for it is a category error we won't make, because the night is more interesting than the error.

In short. The biggest natural growth-hormone bursts happen in deep sleep. Cut that stage and the peak shrinks. A receptor ligand does not replace a night.

Ageing thins N3, fragments continuity, and leaves a hypnogram that looks moth-eaten even when total time in bed has not fallen. Nocturnal GH amplitude falls with that thinning, and with the abdominal adiposity that often arrives in the same decades. A secretagogue literature can still raise a daytime GH peak in an older animal. It has not restored a young-adult night, and it shouldn't be asked to in a single sentence. Thyroid hormone remains permissive; a hypothyroid somatotroph writes fewer granules whatever the analogue. Glucocorticoids in excess suppress the axis, which is one of the crueller ironies of a dirty secretagogue that also raises cortisol. Sex steroids shape amplitude and frequency across the adult lifespan. The somatotroph is not an isolated oscillator that a pair of cakes can retune in isolation from a clock, a glucose, a waist, and a thyroid. The sleep-and-glucose essay on this journal is the neighbouring room: cortisol should trough around midnight, melatonin is a darkness certificate, and phones at midnight are still an architecture insult. Send yourself there before anyone reconstitutes anything. A secretagogue literature does not replace a night. That sentence is the whole sleep heading, and it's a kind one.

In short. Ageing, body fat and a wrecked night all flatten the native pulse. The partner essay on sleep and glucose is the control that still costs nothing.

CJC without DAC is a pulse, not a weekly drip, and the absence of the maleimide is the scientific sentence. Native GHRH dies in minutes in plasma because DPP-IV, a serine protease on endothelium and in solution, removes two N-terminal residues from peptides with proline or alanine in the second position. Native GHRH has alanine at position 2 and aspartic acid at position 3. The truncated product does not occupy GHRHR as an agonist. That's why a forty-four-residue hypothalamic peptide, potent at the receptor, is almost useless as a peripheral ligand: the journey from a syringe to a somatotroph is long enough for DPP-IV to finish the job. Mentlein mapped this cleavage family in the 1990s on incretins; the same enzyme is why native GLP-1 dies in about two minutes and why sitagliptin exists. GHRH and GLP-1 are not the same hormone. They share an enemy, and the enemy is rather good at its job. The analogue in this essay chose the receptor, and chose to survive the enzyme by substitution rather than by inhibiting it. That's a chemist's decision with a physiologist's motive. Tens of minutes is still a pulse. Minutes would have been a smear.

In short. An enzyme in blood called DPP-IV cuts native GHRH in minutes and turns it off. Chemists had to change the chain before it could be a useful laboratory ligand.

Four substitutions buy tens of minutes without buying days, which is a rather precise bargain. D-Ala2 is the first and the most famous: replacing L-alanine at position 2 with its D-enantiomer removes the scissile bond DPP-IV wants. The enzyme is stereoselective; a D-residue at P1 is a locked door. Gln8 reduces asparagine rearrangement at the position that is asparagine in native GRF; deamidation is a slow chemical death you'll meet if you leave a reconstituted native sequence on the bench. Ala15 stabilises a helical stretch the receptor likes, glycine being the native residue there. Leu27 replaces an oxidisable methionine, and oxidation is how a perfectly synthesised peptide becomes a mixture after air and time. D-Ala2, Gln8, Ala15, Leu27: four edits, four liabilities, one backbone that still occupies GHRHR with full efficacy. That tetrasubstituted peptide is what the trade calls mod GRF 1–29, and what this catalogue files as CJC-1295 without DAC. The sequence is the product. The absence of the maleimide is the other half of the product. Tens of minutes is still a pulse on a somatotroph's clock. Days would have been a different analogue, and a different question for the liver.

In short. Four amino-acid swaps stop the chain being cut, unfolding, or oxidising. After those edits the analogue lasts tens of minutes, which is still a burst, not a week.

DAC is Drug Affinity Complex, ConjuChem's covalent half-life trick, and it's a beautiful trick for a different question. The chemistry is an N-ε-maleimidopropionyl-lysine on a GHRH-analogue backbone. The maleimide Michael-adds to cysteine 34 of circulating albumin, a free thiol that peptide chemists have been aiming at for decades because albumin's own half-life is measured in weeks. Once conjugated, the peptide rides albumin for days. Clearance slows. Occupancy at GHRHR never quite returns to a trough. The original branded CJC-1295 was this conjugate. Papers that say CJC-1295 and mean the ConjuChem molecule are talking about the albumin adduct, not about tetrasubstituted GRF(1–29) sitting free in plasma. The trade then started selling the unconjugated tetrasubstituted twenty-nine-mer as CJC-1295 without DAC, which is how a catalogue ends up with a name that is a negation. The negation is the scientific sentence. Without the maleimide, modified GRF(1–29) remains a short-acting GHRH analogue that can still pulse. That's the version on the shelf. Flattened weekly GH is a different analogue and a different question. This listing did not stock that question, on purpose.

In short. DAC is a chemical hook that glues the peptide to blood protein for days. Without that hook, the analogue stays short-acting. That absence is the whole point.

Teichman, Neale, Lawrence, Gagnon, Castaigne and Frohman, Journal of Clinical Endocrinology and Metabolism, 2006, 91: 799–805, is the paper the conjugate owes you, and it's a good paper. A single subcutaneous dose of CJC-1295 with DAC produced multi-day elevation of GH and of IGF-1 in healthy adults. The tone was continuous rather than pulsatile. IGF-1 stayed up. That's a real result, in people, with a characterised albumin-conjugating analogue, and it answers the question ConjuChem asked: can you occupy GHRHR for days and move the hepatic integral. You can. The liver wrote IGF-1. What the liver did not write, because nobody asked it to in that design, is a Veldhuis burst series with troughs. Subsequent clinical development of the conjugate did not produce a licensed GHRH medicine; tesamorelin, a different analogue, took that job. The 2006 paper remains the existence proof for flattened GHRH tone. It is also the existence proof that flattened tone is a different object from modified GRF(1–29) without the maleimide. The pulse-length ligand is on this page because of that difference. Two clocks. Two papers. One receptor family. Name which clock you meant and the 2006 result becomes a gift rather than a confusion.

In short. A 2006 study showed that the albumin-glued version keeps growth hormone and IGF-1 raised for days after one dose. That is a flattened signal, not a burst.

Tesamorelin is the licensed neighbour, and naming it is how a research twenty-nine-mer stays a research twenty-nine-mer. It is a trans-3-hexenoyl GRF(1–44), Egrifta in the United States, licensed for reduction of excess abdominal fat in HIV-associated lipodystrophy. The hexenoyl cap is a different DPP-IV-resistance trick from D-Ala2: an acyl group on the N-terminus rather than a stereochemical swap at position 2. The backbone is the full forty-four rather than twenty-nine. Falutz, Allas, Blot and colleagues ran the trials that earned the indication; New England Journal of Medicine 2007 is the paper most people mean. IGF-1 rose. Visceral adipose tissue fell on imaging. Glucose had to be watched, as you'd expect when you raise GH tone in adults. Daily subcutaneous dosing of a still-relatively-short analogue is closer to a pulse series than a weekly albumin conjugate is. Same receptor family. Different backbone, different cap, different legal class, different fridge. Existence proof that GHRHR is drug-able, which is a sentence worth keeping in your pocket. Not a caption for modified GRF(1–29), and not a caption for the blend. A licensed neighbour is a neighbour. It's not the listing.

In short. Tesamorelin is a licensed GHRH medicine for a specific fat-distribution problem in HIV. It proves the receptor can be a drug. It is not this laboratory analogue.

Albumin conjugation is a beautiful trick for a weekly incretin. It is the wrong trick if the message you want is a somatotroph pulse. Semaglutide, tirzepatide and retatrutide use a reversible fatty-acid handle so albumin carries them through the week; the lipid can come off, the reservoir is large, the receptor sees days of tone because the indication asked for days of tone. DAC is covalent rather than reversible, a Michael adduct rather than a hydrophobic parking brake, but the pharmacokinetic idea is cousin to that handle: make the peptide as long-lived as the protein it rides. GHRH, in life, is not a weekly hormone. It is a portal pulse. Gluing it to albumin asks what happens when you take a pulse-generator's ligand and present it as a drip. That question is lawful. It is also a different question from what a slightly prolonged pulse does. Treating the with-DAC and without-DAC molecules as two strengths of one reagent is how you fail the Veldhuis heading and the STAT5b heading in a single table footnote. Copying the incretin half-life trick onto GHRH is how you accidentally run the Teichman experiment when you thought you were running a pulse.

In short. Sticking a peptide to albumin is a clever way to make a weekly drug. Growth-hormone releasing hormone is not a weekly signal, so that trick changes the question.

Ipamorelin occupies GHS-R1a without GHRP-6's ACTH drag, and that clause is why a bench still reaches for this analogue a quarter of a century later. Write the sequence in full, because a five-mer has nowhere to hide. Position 1 is aminoisobutyric acid, Aib, two methyls on the alpha carbon. Position 2 is histidine. Position 3 is D-2-naphthylalanine. Position 4 is D-phenylalanine. Position 5 is lysine, amidated. Aib-His-D-2-Nal-D-Phe-Lys-NH2. The D-residues and the Aib are why plasma aminopeptidases have a harder time than they would with an all-L pentapeptide of equivalent mass. Minutes, for a secretagogue, are the useful window: long enough to occupy GHS-R1a through a burst, short enough that a trough can still happen. Novo Nordisk published it. Raun et al., European Journal of Endocrinology, 1998, 139: 552–561. In vitro, on rat pituitary cells, it released growth hormone. In vivo, in swine and in rats, plasma GH rose. ACTH, cortisol and prolactin did not, at doses that were effective for GH, in contrast to GHRP-6 and hexarelin run in the same protocols. Selectivity is the entire product, and the tables are how you know. Five letters, one lock, a quiet ACTH line.

In short. Ipamorelin is a five-amino-acid key for the ghrelin receptor. It raises growth hormone and mostly leaves the stress hormones alone.

GHRP-6 is His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, the hexapeptide that proved a second GH-releasing receptor existed before anyone had cloned it. Bowers, Momany, Reynolds, Hong, a run of Endocrinology papers in the 1980s. It released GH. It also released ACTH and prolactin, and cortisol followed the ACTH, which is what corticotrophs do when you occupy their secretagogue-sensitive machinery. Fine if you were cataloguing side-effects. Poor if you wanted GH as the variable. Downstream, cortisol will antagonise some of the IGF-1 pattern, mobilise glucose, and alter immune readouts. Prolactin will confuse a reproductive endpoint. Hexarelin, His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2, did the same circus with more potency. GHRP-2 sat in the family. When Smith's group cloned GHS-R, those ligands had a named target; they still had the off-axis baggage. The secretagogue field then split into cleaner tools and louder ones. A louder one is not a better partner for a GHRH analogue. It is a partner plus a cortisol confound that will change the hepatic programme you thought you were reading as an IGF-1 effect. Cleaner is not a moral word. It's a table with a quiet column.

In short. Older short peptides also raised growth hormone, and they also shoved ACTH, cortisol and prolactin around. That extra noise is a confound if growth hormone was the variable.

Raun 1998 is still the paper, and if you only read one GHS-R paper on this analogue, read this one. The title is the claim: ipamorelin, the first selective growth hormone secretagogue. In vitro, on primary rat pituitary cells, the pentapeptide released GH with a potency and efficacy that sat in the secretagogue family. The dose–response for GH rose. The dose–responses for ACTH and prolactin, run in the same preparations, did not, at concentrations that were already effective for GH. In vivo, in rats and in swine, plasma GH rose after administration. ACTH, cortisol and prolactin did not, at doses that were effective for GH, in contrast to GHRP-6 and hexarelin run in the same protocols. Swine matter because their GH axis is closer to human, on several pharmacological counts, than a rat's is. Selectivity as data, not as a caption. The tables are the argument. If you report a secretagogue IGF-1 rise without showing the ACTH line, you haven't earned the word selective yet, and that's a fixable problem: draw the line. If you use GHRP-6 and then talk as if the IGF-1 were a pure GHS-R1a-to-GH-to-liver path, you've borrowed a corticotroph. Raun didn't. That's why we're still here.

In short. The 1998 paper showed growth hormone rising in dishes and in animals while ACTH, cortisol and prolactin stayed quiet. Those tables are still the reason to use this analogue.

Hunger comes with the receptor, and a recovery caption that treats ipamorelin as a pituitary-only tool hasn't read the clone yet. GHS-R1a is expressed on somatotrophs, which is why a secretagogue raises GH. It is expressed in the arcuate on NPY/AgRP neurons, which is why ghrelin is hunger as well as hormone. It is expressed on vagal afferents, which is why some of the gastric and appetite story is a nerve rather than a pituitary. It is expressed in the enteric nervous system, which is why a later clinical programme could even ask about postoperative ileus — and why the failure of that programme, a missed primary endpoint in a Novo Nordisk and Helsinn file, is information rather than an embarrassment. A clean GH secretagogue is not a universal gut drug. Receptor geography is not a licence to generalise the indication. A catalogue pentapeptide that occupies GHS-R1a will inherit that geography. Modified GRF(1–29) will not, because it occupies GHRHR. The two ligands are how you isolate the two locks. Appetite is not a side-effect in the brochure sense. It is the receptor, doing a job it had before any analogue was synthesised. That's not a bug. That's an address book.

In short. The ghrelin receptor lives on pituitary cells, hunger neurons and gut nerves. A ligand at that receptor inherits all of those addresses, not just the growth-hormone one.

Ipamorelin is not ghrelin, and it's worth saying that in a full sentence. Ghrelin is twenty-eight residues with an octanoyl on serine 3. The analogue does not carry that lipid, does not share the twenty-eight-residue backbone, does not depend on GOAT, and is not the circulating des-acyl majority species. It occupies the same class-A receptor, raises calcium by the same Gq-first route, and inherits the geography of that receptor whether a protocol only sampled GH or not. Length is not a small GHRH either. GHRH is forty-four residues; GHRHR is class B; five residues cannot mimic a class-B ectodomain ligand. If you treat growth-hormone peptide as one substance you've already mixed those objects, and you'll misread both a certificate of analysis and a pituitary-slice paper. Two lengths. Two biosynthetic origins. One granule downstream, if the lock turns. If you write ghrelin mimetic and then treat the analogue as if it were the acylated twenty-eight-mer, you've mixed a synthetic pentapeptide with a stomach hormone. Lawful as a shorthand in a sentence that immediately names the sequence. Unlawful as attribution if a feeding phenotype is then credited to ghrelin when the ligand in the well was Aib-His-D-2-Nal-D-Phe-Lys-NH2.

In short. This five-mer occupies the ghrelin receptor but is not ghrelin, and it is not a short GHRH. Different shapes, different origins, one pituitary cell downstream.

The analogue does not meaningfully bind the motilin receptor, a related GPCR that some ghrelin-family ligands graze. Motilin is a gut peptide. Its receptor is a class-A cousin. Cross-talk at that receptor is how a secretagogue becomes a gastric-motility story whether you asked it to or not. Raun's characterisation included that negative, and it belongs in a write-up that is about to claim a clean GHS-R1a probe. Oral bioavailability is poor, as expected for a pentapeptide with those side chains, those charges, and a digestive tract full of peptidases. Research use in the papers is parenteral in animal protocols, or in vitro. That's a pharmacokinetic fact, not a suggestion, and not a dosing instruction. Non-peptide secretagogues — the mk-series, anamorelin in the cachexia literature — are a different chemical class with their own selectivities and their own clinical programmes. They are not this vial. They belong in a sentence so that secretagogue is not allowed to mean one substance. If the question is oral GHS-R1a agonism in a wasting syndrome, the anamorelin papers are the file. If the question is a selective peptide probe of somatotroph calcium, Raun's analogue is the file.

In short. It does not meaningfully occupy the related gut-hormone receptor for motilin. Swallowed, a chain like this barely survives. Other, non-peptide drugs at the same receptor are a different file.

The blend is ten milligrams of each, freeze-dried together, a twenty-milligram cake, two named sequences, two masses, two retention times, a certificate that names both. CJC without DAC plus ipamorelin, listed as cjc-ipamorelin, is logistics for a reading list that already contained two ligands, the same cap-count decision other pairs in the catalogue have made. It is still GHRHR plus GHS-R1a. It is still Bowers' two G proteins on one granule. It is not a protocol, and it is not a licence to stop attributing the GH peak. The singles remain on the shelf so a bench that wants only GHS-R1a can occupy only GHS-R1a, and a bench that wants only GHRHR can occupy only GHRHR. If you treat the blend as a stronger ipamorelin you've mixed a class-B Gs ligand with a class-A Gq ligand and called the mixture a dose. If you treat the single as a weaker blend you haven't read the receptor sheet. Two cakes. Two questions. A reading list can sit them together. An experiment cannot collapse them and still know which lock turned.

In short. Ten milligrams of each analogue are freeze-dried together. That is two named chains, not one stronger medicine and not a recipe.

Recombinant somatropin is a different listing. Mature human growth hormone is 191 amino acids, about 22 kilodaltons, a four-helix bundle in the class-I cytokine family. The 24 IU vial in this catalogue is that backbone, lyophilised, HPLC-characterised, occupying GHR, recruiting JAK2, phosphorylating STAT5b, asking the hepatocyte to write IGF-1. Occupying GHR directly is a different experiment from occupying GHRHR or GHS-R1a, because you've skipped the somatotroph, skipped somatostatin, skipped the sleep gate, and taken on the flattening problem as your own. A daily subcutaneous bolus of recombinant GH produces a broad plasma peak and a long tail, a pattern closer to a drip than to a Veldhuis burst, and the liver notices. Children with GH deficiency still grow on that regimen because a growing epiphysis will accept a flattened IGF-1 rise. Healthy adults given the same flattened signal are a different population, and acromegaly remains the experiment of nature for what chronic excess does to soft tissue, insulin sensitivity and myocardium. If the question needs a pulse generated by the pituitary, the pulse-length pair is the microphone, not a larger IU count of somatropin.

In short. Injected growth hormone talks to a different receptor and skips the pituitary. Daily injections are a broad peak, not a night burst. That molecule is a separate object.

IGF-1 LR3 is the other neighbour people drag into a recovery sentence, and it belongs one floor further down. Francis, McDougall, Bagley, Ballard and colleagues made Long Arg3 IGF-1 by substituting Glu3 for arginine and adding a thirteen-residue N-terminal extension. IGF-binding-protein affinity collapses. IGF1R agonism remains. In serum-containing culture the analogue is the ligand the myoblast actually sees. It does not occupy GHRHR. It does not occupy GHS-R1a. It does not occupy GHR. It occupies a receptor tyrosine kinase, and glucose belongs in that protocol because hybrid insulin receptors are real. If you reconstitute modified GRF(1–29), ipamorelin and LR3 into one experiment you've mixed two GPCRs on a somatotroph with an RTK on a myotube. Lawful, if three questions are named. Unlawful as attribution, if a single waist measurement is then credited to the GH axis. The 83-mer has its own essay. The 191-mer has its own essay. This pair has this one. Walk GHRH and ghrelin to GH to IGF-1, in that order, if the axis is the object. Skip to the kinase if the kinase is the object. Write which skip you made. Skips are allowed. Hidden skips are how a neighbourhood becomes a muddle.

In short. A lab form of IGF-1 talks to a different receptor on muscle and other cells. It is not a GHRH analogue, not a secretagogue, and it does not answer the same question.

Four laboratory analogues sit on four microphones of the same axis, and confusing them is how a journal becomes a stack. Modified GRF(1–29) without DAC asks what a slightly prolonged GHRH pulse does to somatotrophs, to GH burst mass, and to the hepatic STAT5b programme when troughs are still allowed. Ipamorelin asks what selective GHS-R1a agonism does to the same granule, and to arcuate and gastric addresses, without dragging ACTH and prolactin into the table. Recombinant somatropin asks the GH receptor itself, skipping the hypothalamus and the pituitary. IGF-1 LR3 bypasses the pituitary and the liver and asks the tyrosine kinase on a myotube or a hepatocyte, with binding proteins taken out of the fight. Four ligands, four receptors, four questions. The axis essay on this desk is the wiring they share. This essay is the pair, at the length a recovery search actually needs, with sleep left on the diagram. Confuse the four and you are assembling a stack. A stack is not an experiment. Attribution is the job, and it's a more interesting job than a caption. Sequence identity is the only honest link between a catalogue vial and a paper.

In short. Four related peptides ask four different receptors on the same hormone axis. Mixing them hides which one worked. This essay is the two-switch pair.

Identity first. HPLC and mass spectrometry on the reconstituted stock, because lyophilised peptides are hygroscopic, labels smudge, and the tube you think is the twenty-nine-mer is, in a crowded freezer, sometimes the pentapeptide. Modified GRF(1–29) without DAC and ipamorelin cannot hide as each other on a mass spectrometer: tens of residues versus five, a maleimide either present or honestly absent, 711.9 daltons on the pentapeptide if the certificate is telling the truth. A blend cake should show two main peaks and two masses. A certificate that cannot show those has not yet named the microphones; it is a rumour about a white powder. Vehicle matched. Serum stated, because serum is a protease bath and a VEGF bath and a DPP-IV bath. Then the concentration you actually measured, not a nominal microgram-per-millilitre from a label that assumed the cake was dry. None of those sentences is a dose for a person. All of them are how a pituitary-slice paper starts, and they're how you'd start if you wanted a peak you could attribute. Reverse the order and you will photograph a GH rise. You will not know which chain earned it. Knowing is the interesting part.

In short. Weigh both chains on a mass spectrometer first. The short GHRH analogue and the five-mer cannot hide as each other. Then name the amounts you actually put in.

Sampling and state are the rest of the write-up, and they're the half that turns a peak into a pulse. Frequent GH if the pulse is the question, every ten or twenty minutes around the dose, a deconvolution if you have the kit. IGF-1 if the hepatic integral is the question, knowing you have traded bursts for a running mean. ACTH, cortisol and prolactin if the pentapeptide's selectivity claim is supposed to survive the experiment, because mixed pituitary cells are still mixed and an intact HPA axis is still intact. Metabolic state of the animal, because glucose and fasting gate the somatotroph; a fed challenge and a fasted challenge are not the same assay. Time of day, because a daytime secretagogue probe is not a nocturnal endogenous pulse. Sleep, if you are in an intact animal, because missing slow-wave sleep is how you subtract the largest native contribution and then credit the analogue for a number the night already owned. Species: rodent sexual dimorphism of GH pattern is sharper than human; swine sit closer on some secretagogue counts, which is why Raun used them. Write those variables. A recovery caption will not write them for you.

In short. Take frequent growth-hormone samples if you care about bursts. Write whether the animal had slept, eaten or been fasted. Those details change the number.

If you apply both ligands, run the factorial: GHRH analogue alone, ipamorelin alone, both, neither, on a named readout, with both concentrations written down. Until that figure exists in a paper you trust, the stack is a rhyme. A bench that ran the factorial once would teach the field more than a hundred threads repeating the rhyme, and it would be a pleasure to read. Add a somatostatin analogue if you want to know whether the stop can still win. Add a dihydropyridine if the L-type current is the claim. Add GHRP-6 in a comparator well if the selectivity claim is the claim; the ACTH line should move in one column and not the other. Scrambled peptide, vehicle, a positive control that must work or the week is void. Blinded scoring of the GH curve, because hope enters a sparse sampling schedule faster than it enters a deconvolution. The pair will survive contact with a proper control. If it does not, it was not what the caption said, and that is a result worth publishing. Phenotype rhyme — both look like GH went up — is the weakest reason to co-administer two ligands, and the most common.

In short. If you use both peptides, test each one alone and both together, and write both amounts. A rhyme in a forum is not a ratio in a dish.

What you should leave with is a topology, not a shopping list. Somatotrophs have two on-switches: GHRH via Gs and GHS-R1a via Gq. Bowers already showed the pair is more than additive. CJC without DAC is tetrasubstituted GRF(1–29), DPP-IV-resistant, tens of minutes, still a pulse, deliberately without the maleimide that would glue it to albumin for days. Ipamorelin is Aib-His-D-2-Nal-D-Phe-Lys-NH2, GHS-R1a, Raun 1998, GH up, ACTH and prolactin mostly quiet at GH-effective doses. Somatostatin remains the off-switch. Veldhuis remains the reason the pulse is the design constraint. The largest native bursts still fire in slow-wave sleep; a secretagogue literature does not replace a night. The blend is ten milligrams of each. Recombinant somatropin is a different listing, the 191-residue ligand at GHR. Tesamorelin is the licensed GHRH neighbour in its indication. Four microphones on the axis; this page is the two-switch pair a recovery search actually lands on. If your experiment needs the pair, name both. If it needs a medicine, this catalogue does not sell one. That's the map, and the map is the useful thing to carry out of the room.

In short. Leave with the map: two switches, a pulse-length GHRH copy, a clean ghrelin-receptor key, sleep still owning the native burst, and injected growth hormone as a separate object.

The neighbouring essays take the rest of the map, and they're worth the walk. CJC-1295 without DAC: why the maleimide is absent, why tesamorelin is named, why tens of minutes is a scientific number rather than a compromise. Ipamorelin: Raun's tables, the pentapeptide sequence, the failed ileus programme as a reminder that selectivity is not a universal drug. The growth-hormone axis, properly explained: four microphones, four questions, the wiring this pair sits on. Somatropin: the 191, JAK2–STAT5b, adult-GHD composition trials, acromegaly as caution. Sleep, cortisol and glucose: Van Cauter's restriction work, the midnight cortisol trough, why a wrecked night wrecks breakfast. How peptides talk to cells: occupancy, amplification, arrestin, the class-B and class-A distinction this pair uses on two sides of a synergy. Read those if you are holding a single vial, or if you wanted the night rather than the pair. Stay here if you wanted to know why Bowers' two locks sit in one cake, why the Drug Affinity Complex was left off, and why a scored slow-wave night is still the control that costs nothing. The night is still free. The pair is still two different jobs. Both facts can sit in the same head.

In short. Other essays cover each analogue, the full axis, injected growth hormone, and the sleep night. This one exists to keep the recovery search from collapsing them.

Protocols, doses and combinations live in the papers, not on this page. The studies that already ran GHRH analogues, secretagogues, recombinant GH and IGF-1 analogues in animals and in dishes are in PubMed, with concentrations, sampling intervals and exclusion criteria. Go there if you are running an experiment. Stay here if you wanted the pair explained at the depth a Cell desk would allow a review. Tesamorelin remains the licensed GHRH analogue in its indication. Recombinant somatropin remains a medicine in diagnosed deficiency. The tetrasubstituted twenty-nine-mer and the selective pentapeptide remain characterised ligands for two receptors on one secretory cell, pulse-length by design, sitting on an axis whose physiology was worked out before any of us were stocking it. The axis will still pulse tonight, whether or not anyone opened a vial, because the hypothalamus and the stomach and the somatotroph were not waiting for a chromatogram. Slow-wave sleep will still own the largest native burst. The figure is a late readout. The receptors were early. The pair was two different jobs. That's a cheerful fact, if you like physiology, and we do.

In short. This is the explanation, not a dosing plan. The pituitary will still release growth hormone in bursts tonight, whether or not anyone uses the analogues.

Research-use-only. Not for human consumption / not a medicine. The lyophilised CJC without DAC and ipamorelin on these listings, including the twenty-milligram blend that is ten milligrams of each, are laboratory reagents, HPLC-characterised, labelled for in-vitro work and for the animal protocols a bench already knows how to write: a pituitary-cell GH assay, a two-receptor synergy experiment whose concentrations you actually name, a secretagogue challenge whose ACTH line you actually draw, a frequent-sampling curve that can see a burst. The physiology in the paragraphs above is public, cited, and older than either vial. Use it to design the experiment you have the controls for, with both locks named, the stop named, the night named, and the time point written down. Read Bowers, read Raun, read Veldhuis, read Teichman so you know which CJC you did not reconstitute, then weigh the cake. We will sell you the named sequences. We will not tell you they are a night's rest, and we will not tell you they are recombinant somatropin. Two on-switches. One granule. Sleep still owns the native pulse. That's the whole of the kindness this page can do, and it's enough.

In short. These sequences are research chemicals for experiments, not medicines. Weigh them, measure the bursts and the stress hormones, and keep the claim the size of the tables.