RESEARCH DIGEST / MECHANISM
Sermorelin is the GHRH(1-29) fragment that prompts the body's own pulsatile growth hormone.
It clears the plasma in roughly ten minutes, yet holds serum GH elevated for about three hours. This is a mechanism-first reading of the published record, with every quantitative claim carried back to its study.
The short version
Sermorelin is a small peptide — a chain of 29 amino acids — that copies the front end of GHRH (the brain's own "make growth hormone" signal). Instead of supplying growth hormone directly, it taps the pituitary gland and tells it to release its own, in the natural bursts the body uses (what researchers call pulsatile release). When growth hormone rises, the liver makes more IGF-1 (a growth signal that carries out many of growth hormone's effects). This page is the overview; the deeper pages cover the sermorelin mechanism of action, the studied doses and routes, and the full reference list.
What is sermorelin?
Sermorelin (sermorelin acetate) is the amidated synthetic 29-amino-acid peptide corresponding to the amino-terminal 1-29 fragment of human growth hormone-releasing hormone (GHRH) — a 44-residue hypothalamic hormone. The 1-29 stretch is the shortest fragment that keeps full activity at the GHRH receptor, which is why a peptide less than two-thirds the length of native GHRH reproduces its core signaling. It is a pituitary growth hormone secretagogue (a secretagogue is something that tells a gland to release its hormone), studied for its ability to drive the body's own GH output rather than replace it [1].
The regulatory history is specific and frequently misstated, so it is worth stating plainly. Sermorelin was an FDA-approved prescription drug for the evaluation and treatment of growth hormone deficiency and short stature in children, and it was withdrawn from the US market in 2008 for commercial reasons — not because of any safety or efficacy problem [5]. It is no longer marketed as a finished branded product; it is now prepared by compounding pharmacies and is treated as a long-standing Category 1 bulk drug substance under the FDA's Section 503A framework (final guidance January 2025). The accurate framing is a formerly FDA-approved GHRH analog that is now compounded — neither a currently marketed approved drug nor a compound that was never sanctioned.
Sermorelin as a research peptide: GHRH(1-29)NH2
As a research peptide, sermorelin is defined by its sequence. It is GHRH(1-29)NH2 — the amidated 1-29 N-terminal fragment of GHRH, identical in those 29 residues to the native hormone, with a C-terminal amide that the bioactive fragment carries. Its molecular weight is 3357.9 Da and its molecular formula is C149H246N44O42S; the CAS number for the parent peptide is 86168-78-7 [1]. Because aqueous peptide solutions degrade, research-grade sermorelin is supplied as a lyophilized (freeze-dried) powder and reconstituted with sterile diluent before use.
The peptide's biological identity is the whole story here. It is not a steroid, not a hormone-replacement product, and not a controlled substance. It is a GHRH analog: a molecular key cut to fit the GHRH receptor on the pituitary's growth-hormone cells. What follows on this site is the published record of what that key does once it turns the lock — the receptor pharmacology, the dose-response data, and the open questions, all sourced.
What does sermorelin do to the body?
Sermorelin binds GHRH receptors on anterior-pituitary somatotrophs — the cells that make growth hormone — and prompts them to synthesize and release GH in the body's own pulsatile pattern (the natural bursts, rather than a steady drip). Because it acts upstream on the pituitary instead of supplying GH from outside, the normal brakes stay on: somatostatin (the hormone that opposes GHRH) and IGF-1 negative feedback continue to regulate the system, which preserves the pulsatile rhythm [1]. The downstream consequence of higher GH is more hepatic IGF-1, the liver-made growth signal through which much of GH's activity is carried.
The clinical signature of that mechanism is documented. In healthy men, intravenous GHRH(1-29) released GH at doses as low as 0.25 mcg/kg, with maximal release at 1-2 mcg/kg; despite rapid clearance the GH rise lasted about three hours [3]. In prepubertal growth-hormone-deficient children, once-daily subcutaneous GHRH(1-29) raised first-year height velocity from roughly 4.1 cm/year to about 7-8 cm/year, without excessive IGF-1 generation [2]. The receptor-level account — the GHRH-receptor pharmacology and the sermorelin half-life — is detailed on the mechanism page, while the deeper findings, including the aging and GH/IGF-1 research, the cognition and sleep findings, and the safety and tolerability record, live on the research page.
Sermorelin vs ipamorelin: what is the difference?
Sermorelin and ipamorelin are often discussed together because both raise growth hormone, but they act on two different receptors. Sermorelin is a GHRH analog: it works at the GHRH receptor, the class B G-protein-coupled receptor that native GHRH uses. Ipamorelin belongs to the growth-hormone-releasing peptides (GHRPs) — a separate class that acts on the ghrelin/GHS receptor, a different switch entirely [1]. The two mechanisms are complementary rather than redundant, which is why GHRH analogs and GHRPs are sometimes studied side by side. This site documents the GHRH-receptor arm; it does not present any human stacking protocol, and the dealt literature here reports the GHRH pathway rather than combination outcomes.