Growth Hormone Peptides Explained: GHRH Analogues, Ghrelin Mimetics and How the Research Compares

In 1976, an endocrinologist at Tulane University and his colleagues made a small synthetic peptide that released growth hormone from the pituitary, and nobody, including them, knew exactly why it worked. The receptor it acted on would not be found for another twenty years, and the natural hormone it was imitating would turn up, of all places, in the stomach. That back-to-front history is the reason the growth hormone peptides fall into two quite different families today.

This guide maps the whole family: why there are two families of growth hormone peptides (GHRH analogues and ghrelin mimetics), how they were found, how each member differs in half-life, selectivity and pulse shape, why researchers pair one from each side, and where IGF-1 fits. Every compound mentioned here is sold by Crown Peptides strictly for laboratory research use only, and this guide is written for readers interested in the science. Each compound links to its full guide, and the whole range sits in our Endocrine & Hormonal research peptides category.

What Are Growth Hormone Peptides, and Why Do They Not Contain Growth Hormone?

"Growth hormone peptides" is the everyday name for a group of short, mostly synthetic peptides that prompt the pituitary gland to release its own growth hormone. That is the key point, and the one most often misunderstood: none of them is growth hormone. Growth hormone itself is a large protein of 191 amino acids. The peptides in this family are signals that ask the pituitary to release more of it, in the body's own rhythm.

What does "growth hormone secretagogue" mean?

A secretagogue is anything that makes a gland secrete, so a growth hormone secretagogue (GHS) is any molecule that makes the pituitary release growth hormone. In practice "GHS peptides" usually means the ghrelin-receptor side of the family, while "GH peptides" is used loosely for everyone.

What are GHRH peptides and GHRP peptides?

GHRH peptides are modified versions of growth hormone-releasing hormone, the brain's own instruction to release growth hormone. GHRPs, or growth hormone-releasing peptides, are small synthetic peptides that act on a different receptor, the one that responds to the stomach hormone ghrelin. Both families reach the same pituitary cells, through different doors.

Why Are There Two Families? Two Switches on the Same Cell

This is the heart of the story. The growth hormone-making cells of the pituitary, the somatotrophs, carry two separate receptors that can switch release on.

The GHRH receptor

The first switch is the GHRH receptor. When it was cloned in 1992, it turned out to be found predominantly, if not exclusively, in the anterior pituitary, and to be related to the receptors for secretin and vasoactive intestinal peptide (VIP). When GHRH binds it, the cell raises its levels of an internal messenger called cyclic AMP (PMID: 1333056). Sermorelin, CJC-1295 and Tesamorelin all act here.

The ghrelin receptor, GHS-R1a

The second switch is the growth hormone secretagogue receptor, GHS-R1a, now usually called the ghrelin receptor. Merck scientists cloned it in 1996 from the pituitary and hypothalamus of pigs and humans, and showed it was the target of the synthetic secretagogues (PMID: 8688086). GHRP-6, GHRP-2, Hexarelin and Ipamorelin all act here.

Different wiring inside the cell

The two receptors use different internal wiring. In a Merck study of rat pituitary cells, GHRH tripled cyclic AMP, while GHRP-6 on its own did not change it at all. A GHRH-receptor blocker left GHRP-6 working normally, and together, at maximal concentrations, the two were synergistic (PMID: 2541999). Two receptors on one cell, wired to different messengers, explain why there are two families, and are part of the reason they are so often studied together.

The brake: somatostatin

Release is also held back by a brake, the hypothalamic hormone somatostatin. A Turin review noted that inhibitory influences, somatostatin included, that almost abolish the effect of GHRH only blunt GHRPs, which act at both the pituitary and the hypothalamus (PMID: 9186261). Bowers described a curious pattern: given into a vein, GHRPs release more growth hormone than GHRH in people, yet the reverse is true in a dish of pituitary cells, which he linked to their need for the body's own GHRH (PMID: 22975043).

A Detective Story in Reverse: How the Family Was Found

Most hormones are found first and copied later. This family did it the other way round.

Synthetic peptides first, with no known receptor

Cyril Bowers and colleagues at Tulane began making small synthetic peptides in the 1970s. By 1984 they had described a hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, later named GHRP-6, which triggered growth hormone release in rats, monkeys, lambs and calves without releasing LH, FSH, TSH or prolactin in their tests (PMID: 6714155). Looking back in 2012, Bowers wrote that GHRPs were first imagined to be analogues of GHRH, but by comparing the two between 1982 and 1984 his group came to suspect they reflected a new hormone regulator of growth hormone, one yet to be identified (PMID: 22975043).

GHRH found in a tumour

The brain's own releasing hormone was finally pinned down in 1982, not from a brain but from pancreatic tumours that had caused acromegaly by over-stimulating the pituitary. Roger Guillemin's team isolated a 44-amino-acid peptide with full growth hormone-releasing activity (PMID: 6812220), and a separate team led by Jean Rivier and Wylie Vale characterised a growth hormone-releasing factor from a similar tumour the same year (PMID: 6292724).

The receptor, then the hormone

The 1996 receptor cloning suggested the synthetic peptides were mimicking an undiscovered hormone (PMID: 8688086). In 1999, a Japanese team led by Masayasu Kojima and Kenji Kangawa found it in rat stomach: a 28-amino-acid peptide with an octanoyl fatty acid attached to its third amino acid, a modification essential for its activity. They named it ghrelin, from a Proto-Indo-European root meaning "grow" (PMID: 10604470). The family finally had a natural parent.

The Growth Hormone Peptide Family Map

Here is every growth hormone peptide in our range, its family, and what sets it apart.

• Sermorelin (GHRH side): the first 29 amino acids of human GHRH, a short fragment that keeps about half the full hormone's potency, with no added protection.
• CJC-1295 (With DAC) (GHRH side): a modified 29-residue GHRH chain with an albumin-binding hook and a half-life measured in days.
• CJC-1295 (No DAC) (GHRH side): the same modified chain without the albumin hook, supplied in our CJC-1295 (No DAC) + Ipamorelin (Blend).
• Tesamorelin (GHRH side): all 44 amino acids of human GHRH with a small protective cap, and the deepest human trial record on this side of the family.
• GHRP-6 (ghrelin-mimetic side): the six-amino-acid GHRP that made the field.
• GHRP-2 (ghrelin-mimetic side): a more potent cousin of GHRP-6 that became a diagnostic medicine in Japan.
• Hexarelin Acetate (ghrelin-mimetic side): one of the strongest growth hormone releasers in the family, and also a binder of CD36, a receptor found in heart tissue.
• Ipamorelin (ghrelin-mimetic side): a five-amino-acid peptide described as the first selective secretagogue, which in pig studies released growth hormone without the cortisol rise of older GHRPs.
• Tesamorelin + Ipamorelin (Blend) (both sides): one vial carrying a GHRH analogue and a ghrelin mimetic together.
• IGF-1 LR3 (downstream): not a secretagogue at all, but a long-lasting analogue of IGF-1, the main signal growth hormone produces.
• MGF and PEG-MGF (downstream): peptides based on a locally made splice variant of IGF-1, studied in tissue biology.

The GHRH Side: Sermorelin, CJC-1295 and Tesamorelin

Natural GHRH is long, and an enzyme in blood called DPP-4 quickly clips the first two amino acids off its front end. Unprotected GHRH, including the 29-residue fragment, is rapidly cut at that point in plasma, and swapping in a mirror-image D-amino acid at position 1 or 2 prevents it (PMID: 2565342). Each analogue below solves that problem in a different way.

Sermorelin: the 29-amino-acid fragment

In 1984, Nicholas Ling and colleagues synthesised shortened versions of GHRH and found that fragments ending at residue 29, 30 or 31 kept about 50% of the full hormone's potency on rat pituitary cells; shorter fragments still worked, but with very low potency (PMID: 6435620). GHRH(1-29)-NH2 became Sermorelin. In a study of 10 healthy older men, two weeks of GHRH(1-29) at the higher of two amounts tested raised 24-hour growth hormone, pulse size and IGF-1 to the point where they no longer differed from those of young men (PMID: 1379256). The full story is in our Sermorelin guide.

CJC-1295: with and without DAC

CJC-1295 takes the 29-residue chain, makes four amino acid substitutions to protect it from enzymes, and in its best-known form adds a reactive group (the "DAC", or drug affinity complex) that latches permanently onto blood albumin. In rats it was still present in plasma beyond 72 hours (PMID: 15817669). In healthy adults, a single administration raised average growth hormone 2- to 10-fold for 6 days or more and IGF-1 1.5- to 3-fold for 9 to 11 days, with an estimated half-life of 5.8 to 8.1 days (PMID: 16352683). The No DAC version drops the albumin hook, making it a much shorter-lived signal; most published human data belong to the DAC form. See CJC-1295 With DAC vs Without DAC and our CJC-1295 with DAC guide.

Tesamorelin: the full-length answer

Tesamorelin is the complete 44-amino-acid hormone with a small trans-3-hexenoyl group added to its first residue, which shields it from DPP-4. It has the most substantial human record on the GHRH side. Its best-known result comes from a 26-week randomised, placebo-controlled trial in 412 HIV patients carrying extra abdominal fat: visceral fat fell by 15.2% on tesamorelin against a 5.0% rise on placebo, while IGF-1 climbed by 81.0% (PMID: 18057338). Our Tesamorelin guide tells its story.

How the GHRH analogues compare

Put simply, Sermorelin is the bare working fragment, CJC-1295 is a protected fragment that can be made to last days, and Tesamorelin is the protected whole hormone. Our comparisons cover each pair: CJC-1295 vs Sermorelin, Sermorelin vs Tesamorelin and Tesamorelin vs CJC-1295.

The Ghrelin-Mimetic Side: GHRP-6, GHRP-2, Hexarelin and Ipamorelin

The ghrelin mimetics are short, six amino acids or fewer, and all carry protective mirror-image D-amino acids. Where the GHRH analogues differ mainly in how long they last, these differ mainly in what else they release.

GHRP-6: the original

GHRP-6 is the hexapeptide that put the field on the map, and the first to be studied extensively in people (PMID: 6714155). In healthy men, prolactin and cortisol rose about two-fold, but only at the highest amount tested (PMID: 2108187). Our GHRP-6 guide covers it in full.

GHRP-2: the potent one that became a diagnostic

GHRP-2 swaps in different unnatural amino acids for greater potency. In pig studies it showed higher potency but lower maximal effect than GHRP-6, and, like GHRP-6, it raised ACTH and cortisol (PMID: 9849822). Its biggest claim to fame is clinical: in a Japanese validation study, growth hormone peaks after GHRP-2 were dramatically lower in adults with growth hormone deficiency than in healthy people, enough to support a simple diagnostic test (PMID: 17609397). See our GHRP-2 guide, how GHRP-2 became a diagnostic drug and GHRP-2 vs GHRP-6.

Hexarelin: a strong releaser with a heart connection

Hexarelin is GHRP-6 with a methyl group added to its D-tryptophan. In 12 healthy young volunteers, it released about twice as much growth hormone as GHRH given by the same route, and the response was very reproducible (PMID: 8126144). Like GHRP-6, it can raise prolactin, ACTH and cortisol (PMID: 11238504). What sets it apart is a second receptor: Hexarelin binds CD36 in rat heart tissue, and its effect on coronary perfusion pressure was missing in hearts from mice lacking CD36 (PMID: 11988484). Our Hexarelin guide covers the cardiac research.

Ipamorelin: the selective one

Ipamorelin, a five-amino-acid peptide from Novo Nordisk, was described by its developers in 1998 as the first secretagogue selective for growth hormone. It released growth hormone about as well as GHRP-6, yet in pigs it left ACTH and cortisol at GHRH-like levels even at very high amounts (PMID: 9849822). That selectivity helps explain why it is the ghrelin-side partner in both of our blends. The Ipamorelin guide has the full story, and GHRP-6 vs Ipamorelin and Ipamorelin vs GHRP-2 compare it with its older relatives.

MK-677: the non-peptide relative

MK-677 (ibutamoren) is not a peptide at all. It is a small molecule that acts on the same ghrelin receptor and is active by mouth. In a two-year randomised trial in 65 healthy older adults, it raised growth hormone and IGF-1 to young-adult levels, but also raised fasting glucose, reduced insulin sensitivity and increased appetite (PMID: 18981485). Crown Peptides does not stock MK-677; our MK-677 vs Ipamorelin article explains how it compares.

How Do Growth Hormone Peptides Differ From Each Other?

Within each family, members differ in how long they last, what else they release, and the shape of the signal they produce.

Half-life: minutes, hours or days

The family covers an extraordinary range. Unprotected GHRH fragments like Sermorelin are rapidly cleaved by DPP-4 (PMID: 2565342). In healthy men, Ipamorelin was cleared with a half-life of roughly 2 hours (PMID: 10496658). CJC-1295 with DAC, riding on albumin, lasted 5.8 to 8.1 days (PMID: 16352683). Our guide to peptide half-life explains why such small changes in structure make such large differences.

Selectivity: what else gets released

The GHRH analogues are naturally selective, because their receptor is found predominantly, if not only, in the anterior pituitary (PMID: 1333056). The ghrelin mimetics vary. GHRP-6, GHRP-2 and Hexarelin can raise cortisol and prolactin to varying degrees, and ghrelin itself raised prolactin, ACTH and cortisol more than Hexarelin did in a Turin study of seven young men (PMID: 11238504). Ipamorelin stands out as the exception, with selectivity for growth hormone similar to that of GHRH (PMID: 9849822).

Appetite: the ghrelin receptor's other job

The ghrelin receptor is not only a growth hormone switch. In a randomised, double-blind crossover study in nine healthy volunteers in London, ghrelin infusion increased the energy every single person ate from a free-choice buffet, by an average of 28%. The authors called it the first circulating hormone shown to stimulate food intake in man (PMID: 11739476). That second job is why appetite features in ghrelin-mimetic research and hardly at all on the GHRH side.

Pulse shape: a spike or a raised floor

The body releases growth hormone in bursts, so the shape of the signal matters as much as its size. After a single 15-minute infusion in healthy men, Ipamorelin gave one burst of growth hormone that topped out at 0.67 hours and then faded away (PMID: 10496658). Over two weeks in 13 healthy men, daily tesamorelin made the body's own pulses bigger, lifted baseline secretion and raised IGF-1 by 181 micrograms per litre (PMID: 20943777). CJC-1295 with DAC kept pulsatility intact while raising the trough levels between pulses 7.5-fold, lifting mean growth hormone by 46% and IGF-1 by 45% (PMID: 17018654). In these studies, then, a single dose of a short ghrelin mimetic produced a brief spike, while GHRH analogues, especially long-acting ones, also lifted the floor between pulses.

Desensitisation: does the response fade?

Repeatedly stimulated receptors can tire. Rat pituitary cells pre-treated with GHRP-6 responded less to a second GHRP-6 challenge but normally to GHRH, and recovered within an hour (PMID: 2541999). In a Manchester study in older adults, 16 weeks of repeated Hexarelin reduced the growth hormone response to a Hexarelin challenge from an area under the curve of 19.1 to 10.5 microgram-hours per litre; four weeks after stopping, it was back to 19.4. The authors called it a partial and reversible attenuation (PMID: 9589671).

Why Researchers Pair One Peptide From Each Family

The most striking finding in this field is synergy: signals from the two receptors, sent together, release more growth hormone than both would added up. Among 11 healthy adults studied in Belgrade, GHRH plus GHRP-6 released nearly twice the sum of each given alone, and the extra effect vanished in patients whose pituitary was cut off from the hypothalamus (PMID: 7883854). In one London study the synergy faded when the pair was repeated (PMID: 8762732).

That biology is the thinking behind our CJC-1295 (No DAC) + Ipamorelin (Blend) and Tesamorelin + Ipamorelin (Blend), though neither exact pair has yet been tested together in a published study. The evidence is set out in our two-pathway CJC-1295 and Ipamorelin article and our Tesamorelin + Ipamorelin blend guide, and Ipamorelin vs Sermorelin sets one member of each family side by side.

After the Pulse: IGF-1 and the Signals Downstream

Much of what researchers measure after a growth hormone peptide is IGF-1, insulin-like growth factor 1, made mainly by the liver in response to growth hormone.

Why IGF-1 is the number everyone measures

Growth hormone comes and goes in pulses, while IGF-1 changes slowly, making it a running summary of growth hormone activity. But blood levels are not the whole picture. When an NIH team deleted the IGF-1 gene only in the liver of mice, circulating IGF-1 dropped dramatically, yet body weight, body length and femur length were normal, pointing to the importance of IGF-1 made locally in tissues (PMID: 10377413).

IGF-1 LR3: skipping the secretagogue step

IGF-1 LR3 is a modified IGF-1 with very low affinity for the IGF-binding proteins that normally hold IGF-1 in check. In rats it was cleared from the circulation more quickly than IGF-1, yet given by continuous infusion it was generally 1.5 to 2 times more potent for changes in body weight gain and organ weights (PMID: 8708565). It lets researchers study the downstream signal directly, bypassing the pituitary. See our IGF-1 LR3 guide.

MGF and PEG-MGF: the local variant

The IGF-1 gene can be spliced in different ways, and one variant, mechano growth factor, is made locally in tissue. In a University College London cell study, the distinct E-domain peptide of MGF increased myoblast proliferation and inhibited terminal differentiation, apparently through a receptor other than the IGF-1 receptor (PMID: 12095637). Our MGF guide and PEG-MGF guide cover both forms.

Which Growth Hormone Peptides Became Licensed Medicines?

Several members, or close relatives, have been licensed by regulators, some of them as diagnostic tools.

Sermorelin in the United States

Sermorelin was licensed by the US Food and Drug Administration as Geref, first approved in 1990. The manufacturer discontinued it in 2008, and the FDA later determined that it was not withdrawn for reasons of safety or effectiveness (Federal Register, 2013).

Tesamorelin in the United States

In the United States, tesamorelin holds a licence as Egrifta for reducing excess abdominal fat in adults with HIV-associated lipodystrophy, on the strength of trials like the one above (PMID: 18057338). It is not licensed in the UK.

GHRP-2 in Japan

GHRP-2, also called pralmorelin, is marketed in Japan by Kaken Pharmaceutical as a single-dose diagnostic agent for assessing growth hormone deficiency, the story told in our article on how GHRP-2 became a diagnostic drug.

Macimorelin and anamorelin: the small-molecule cousins

Macimorelin, an oral ghrelin-receptor agonist, was approved by the FDA in December 2017 as Macrilen for diagnosing adult growth hormone deficiency. Its validation trial found 87% sensitivity and 96% specificity against the insulin tolerance test, with 97% reproducibility on retesting (PMID: 29860473). Anamorelin, another ghrelin-receptor agonist, is approved in Japan for cancer cachexia (PMID: 40542284).

The Open Questions Driving Growth Hormone Peptide Research

Some of the most interesting questions in this field are only now becoming testable.

What does the receptor's background signal do? The ghrelin receptor signals even when empty (PMID: 12907757). How much that constant hum contributes to growth hormone release and appetite, compared with ghrelin pulses, is still being worked out.

Can structure explain selectivity? Since 2021, cryo-electron microscopy has shown the ghrelin receptor bound to ghrelin and GHRP-6 (PMID: 34417468) and, most recently, the approved drugs macimorelin and anamorelin (PMID: 40542284). Those structures are starting to show how different agonists steer the receptor's signalling, a step towards understanding why some ghrelin mimetics release growth hormone more cleanly than others.

Which pulse shape matters most? A single dose of a short ghrelin mimetic gives a spike, while long-acting GHRH analogues raise the floor between pulses. In the CJC-1295 study, the IGF-1 rise did not correlate with any single measure of growth hormone secretion (PMID: 17018654). Working out which features of the pattern drive downstream effects is a big open question.

How do modern pairs behave? The classic synergy work paired natural GHRH or its fragments with older GHRPs and ghrelin; pairs such as tesamorelin with Ipamorelin have not yet been characterised together.

The Technical Breakdown: Sequences, Receptors and Pharmacology

Here is the chemistry and receptor detail for those who want it; the rest of the guide stands on its own without this section.

GHRH and its analogues

Human GHRH is Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser-Tyr-Arg-Lys-Val-Leu-Gly-Gln-Leu-Ser-Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met-Ser-Arg-Gln-Gln-Gly-Glu-Ser-Asn-Gln-Glu-Arg-Gly-Ala-Arg-Ala-Arg-Leu-NH2 (PMID: 6812220). Sermorelin is the first 29 residues, ending Ser-Arg-NH2 (PMID: 6435620). DPP-4 removes Tyr-Ala from the N-terminus, and trypsin-like enzymes cut near positions 11 and 12 (PMID: 2565342). CJC-1295 is GHRH(1-29) carrying four substitutions, one of them D-alanine in place of alanine at position 2; the DAC version carries an N-epsilon-3-maleimidopropionamide lysine at the C-terminus that bonds to the free thiol on Cys34 of albumin (PMID: 15817669). Tesamorelin is GHRH(1-44)-NH2 with a trans-3-hexenoyl group on Tyr1.

The ghrelin mimetics

GHRP-6 is His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (PMID: 6714155). GHRP-2 (pralmorelin) is D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2, C45H55N9O6, 818.0 g/mol, and Hexarelin (examorelin) is His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2, C47H58N12O6, 887.0 g/mol (PubChem). Ipamorelin is Aib-His-D-2-Nal-D-Phe-Lys-NH2, which came from a chemistry programme on GHRP-1 analogues without its central Ala-Trp pair (PMID: 9849822). Ghrelin is a 28-residue peptide whose Ser3 carries an n-octanoyl group essential for activity (PMID: 10604470).

Receptor signalling

The GHRH receptor belongs to the class B family of G protein-coupled receptors, alongside the secretin and VIP receptors, and signals through cyclic AMP (PMID: 1333056). GHS-R1a is a G protein-coupled receptor that, in transfected cells, showed strong ligand-independent signalling through inositol phosphate turnover; a substance P analogue acted as a potent full inverse agonist, switching that background activity off (PMID: 12907757). In the cryo-EM structures, both drugs occupied a binding pocket split in two by a conserved salt bridge (PMID: 40542284).

Why most of the family are not oral

In a 1994 pharmacology study of Hexarelin, its biological bioavailability was estimated at 77.0% by the subcutaneous route, 4.8% intranasally and 0.3% by mouth (PMID: 8126144). Poor oral uptake is one reason orally active agonists like MK-677 and macimorelin were developed. These figures describe one study's pharmacology, not guidance for any laboratory work.

Testing a Family of Look-Alike Peptides

Many growth hormone peptides are near-identical. GHRP-6 and Hexarelin differ by one methyl group, 14 mass units apart. Sermorelin and Tesamorelin share their first 29 residues.

That is why identity testing matters: every Crown Peptides batch is checked for purity by HPLC and its identity confirmed by mass spectrometry, with the batch-specific certificate published on our Lab Reports page and the batch number printed on the vial. Our peptide testing guide explains how the two methods work. Vials are supplied freeze-dried and kept cold (see our storage information), weekday orders placed before 2pm are dispatched the same day, and UK delivery is free over £100. If you have a question about a batch, we usually reply within 24 hours on business days, or sooner on WhatsApp, via our contact page.

Related Reading and Compounds

Most of the deeper reading sits in the guides linked above. These are the most useful next steps.

Start with a comparison

If you want one member of each family side by side, Tesamorelin vs Ipamorelin is the clearest place to begin. For differences within a family, try CJC-1295 vs Sermorelin on the GHRH side or GHRP-2 vs GHRP-6 on the ghrelin side.

The two-receptor blends

The CJC-1295 (No DAC) + Ipamorelin (Blend) and Tesamorelin + Ipamorelin (Blend) both put the synergy idea into a single vial.

Growth hormone and sleep

Much growth hormone is released during deep sleep, so our guide to peptides for sleep research covers the growth hormone connection alongside DSIP.

The whole growth hormone family, from Sermorelin to Hexarelin Acetate, sits in our Endocrine & Hormonal research peptides category.

One Hormone, Two Doors, and a Family Still Growing

The growth hormone peptides began with synthetic peptides that worked for reasons nobody understood. It took a cloned receptor and a hormone hiding in the stomach to explain them, and along the way the field produced a selective secretagogue, a GHRH analogue that lasts for days, and licensed medicines in the United States and Japan.

What comes next looks just as interesting: receptor structures that could explain why one ghrelin mimetic is clean and another is not, a clearer picture of which features of the growth hormone pulse really matter, and the first careful studies of modern two-receptor pairs. Two doors into one cell have kept researchers busy for forty years, and there is plenty left to open. Explore every member of the family in our Endocrine & Hormonal research peptides range.

References

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