Sermorelin is the GHRH(1-29) fragment whose pediatric growth-hormone-deficiency trials and adult GH/IGF-1 record are reviewed here.

The short version

Sermorelin is a lab-made copy of the working end of GHRH (the brain's own "make growth hormone" signal). It is a string of 29 amino-acid building blocks — the shortest piece of that natural signal that still does the full job. Given to the body, it tells the pituitary (a small gland under the brain) to release its own growth hormone in natural bursts, which then nudges the liver to make IGF-1, a downstream growth signal. Decades ago it was an approved children's medicine for short stature; today it is studied as a research peptide. This page is a plain reading of what the studies actually measured.

What the sermorelin literature documents

Sermorelin (GHRH(1-29)NH2, also written GRF(1-29)) is a synthetic 29-amino-acid peptide that matches the first 29 residues of human growth hormone-releasing hormone — the shortest fragment that keeps full activity at the GHRH receptor ^[13]. Rather than supplying growth hormone directly, it is a secretagogue (something that tells a gland to release its own hormone): it binds GHRH receptors on the pituitary's growth-hormone-producing cells and prompts the body's own pulsatile GH release — hormone delivered in natural bursts rather than a steady drip — which in turn raises liver-made IGF-1 ^[13].

The record splits into two clear chapters. The first is pediatric: across multicenter trials in growth-hormone-deficient children, once-daily subcutaneous GHRH(1-29) accelerated linear growth, lifting first-year height velocity from roughly 4.1 cm/year toward 7-8 cm/year, without excessive IGF-1 generation ^[1]. That body of work, reviewed in detail on the pediatric growth hormone deficiency research page, is what earned sermorelin a former US approval. The second chapter is adult endocrine research: in healthy older men, 0.5 mg and 1 mg twice daily for 14 days produced dose-related rises in 24-hour GH and IGF-1, and at the high dose those values no longer differed from young men ^[2].

This site reads that record straight. It is editorial commentary on the published literature — a reviewer's digest, not a clinic, not a vendor, and not a course of treatment. Every figure quoted here is captioned with the study it came from, and the full reference list carries every DOI and PubMed link.

From here, the desk opens onto the rest of the record. The full mechanism of action — how a GHRH(1-29) stimulus becomes a pulse of growth hormone — is set out below; the research record gathers the mechanism, the adult endocrine data, and the reported side effects; the half-life and pharmacokinetics explain why the native fragment acts so briefly; the doses studied log what was given to which population; and the common questions answer what readers most often ask, each returned to its study.

Sermorelin peptide: GHRH(1-29) structure and identity

The sermorelin peptide is the amidated 29-residue amino-terminal fragment of the 44-amino-acid hypothalamic hormone GHRH ^[13]. As sermorelin acetate, the salt form, it has a molecular weight of 3357.9 Da, the molecular formula C149H246N44O42S, and CAS number 86168-78-7 (the acetate salt, 114466-38-5). It is the shortest segment of GHRH that retains full biological activity at the GHRH receptor, which is why a 29-residue fragment, not the whole 44-residue hormone, became the molecule of interest ^[13].

That the first 29 residues carry the full punch is not a trivial detail — it is the reason a synthetic peptide of this length could ever have become a usable molecule. The amino-terminal end of GHRH is where the receptor-activating work happens; the rest of the native 44-residue hormone contributes little to potency at the receptor. Trimming to GHRH(1-29) and amidating the C-terminus gave researchers a compound that was easier to make and characterize while behaving, at the receptor, like the whole hormone ^[13].

Because it is the native fragment rather than a chemically stabilized analog, sermorelin clears the bloodstream quickly: its plasma half-life is on the order of 10-12 minutes after intravenous dosing, yet a single dose elevates serum GH for about three hours ^[3]. That gap — minutes in plasma, hours of downstream hormone effect — is itself instructive: the stimulus is brief, but the pulse it triggers and the IGF-1 response that follows outlast it. That brevity is also the structural fact that motivated the longer-acting GHRH analogs, a contrast taken up on the sermorelin vs ipamorelin page.

Sermorelin acetate: the salt form and its identifiers

Sermorelin acetate is the form the compound takes as a stable, characterizable salt — the acetate salt of the GHRH(1-29)NH2 peptide. Its molecular weight is 3357.9 Da, its molecular formula is C149H246N44O42S, and the acetate-salt CAS number is 114466-38-5 (the parent peptide carries CAS 86168-78-7) ^[13]. These identifiers are the molecule's fingerprints; they are how a given material is matched to the substance described in the literature, and they are why "sermorelin" and "sermorelin acetate" point to the same active peptide rather than two different things. The acetate counter-ion does not change the receptor activity — it is simply the salt that makes the peptide practical to handle and store as a lyophilized powder.

Sermorelin mechanism of action: GHRH receptor to pulsatile GH

Sermorelin's mechanism of action runs entirely through the body's own machinery. It binds the GHRH receptor — a class B G-protein-coupled receptor on pituitary somatotrophs (the gland's growth-hormone-making cells) — and activates the adenylate-cyclase / cAMP / protein-kinase-A pathway, raising GH gene transcription and prompting pulsatile GH release ^[13]. Downstream, that GH drives hepatic IGF-1 (a growth signal the liver makes when GH rises) ^[13]. There is also a trophic side to the signal: sustained GHRH-receptor activation supports somatotroph proliferation, not just acute release ^[13].

The defining feature is that the loop stays intact. Because sermorelin acts upstream on the pituitary instead of supplying outside hormone, physiologic feedback through somatostatin (the body's GH brake, abbreviated SRIF) and IGF-1 remains operative, preserving the natural pulsatile pattern ^[13]. In practice that means the system can still say no: when IGF-1 climbs or somatostatin tone rises, the GH response is reined in, rather than the body being forced to absorb a fixed external dose. That negative feedback is real and measurable — classic work showed GH itself exerts autofeedback on the GH response to GHRH, with free fatty acids and somatostatin involved ^[11]. Broader reviews place GHRH inside a multifactorial control system that also includes ghrelin, klotho, and nesfatins ^[12], which is the regulatory backdrop any GHRH analog acts against.

That feedback-preserving design is the crux of the case for a secretagogue over direct hormone replacement. An editorial argued this route is a more physiologic approach to adult-onset GH insufficiency than supplying recombinant GH directly, precisely because it works with the pituitary's own rhythm rather than overriding it ^[4].

What is sermorelin used for?

In the research record sermorelin appears in two main contexts. The first is a historical pediatric use: it was a prescription drug for growth hormone deficiency and short stature in children, since withdrawn from the US market and now prepared by compounding pharmacies. The second is adult GH-axis research, where GHRH(1-29) raised GH and IGF-1 in healthy older men ^[2]. This digest reports those research findings rather than recommending any use.

What is sermorelin?

Sermorelin (GHRH(1-29)NH2) is a synthetic 29-amino-acid peptide matching the first 29 residues of growth hormone-releasing hormone, the shortest fragment that keeps full activity at the GHRH receptor on pituitary cells ^[13]. As sermorelin acetate it has a molecular weight of 3357.9 Da. It is a GHRH analog and a pituitary GH secretagogue, not a form of growth hormone itself.

What does sermorelin do to the body?

It binds GHRH receptors on pituitary somatotrophs and prompts the body's own pulsatile release of growth hormone, which in turn raises liver-made IGF-1 ^[13]. Physiologic feedback through somatostatin and IGF-1 stays intact, so the natural burst pattern of GH secretion is preserved rather than overridden ^[13]. In healthy older men it raised 24-hour GH and IGF-1 over 14 days ^[2].