Sermorelin

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H-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-NH2

YADAIFTNSYRKVLGQLSARKLLQDIMSR

Sermorelin (INN) · GRF (1-29) · GHRH (1-29) · GRF 1-29 amide · Geref (former trade name)

Reported at approximately 11–12 minutes, with the broader literature giving a range of roughly 10–20 minutes. The short half-life reflects rapid peptidase cleavage of the unmodified sequence and is the defining pharmacokinetic feature of the compound.

Native human GHRH is a 44-residue peptide. Sermorelin is its first 29 residues, amidated at the C-terminus — and is described in the literature as the shortest fragment that retains full GHRH receptor activity. Everything else in this compound class is a modification of that same scaffold.

YADAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL

YADAIFTNSYRKVLGQLSARKLLQDIMSR-NH2 The N-terminal 29 residues, amidated. No further modification.

Half-life approximately 11-12 minutes.

The full 44-residue sequence with a C6 hexenoyl group carrying a double bond at position 3, attached to the N-terminal tyrosine.

Reported elimination half-life 8 minutes.

The 29-residue scaffold carrying amino acid substitutions selected for resistance to enzymatic degradation, extending duration relative to unmodified sermorelin.

Sermorelin is therefore the unmodified reference member of the family: the native fragment against which the stabilized analogs are compared. Its first 29 residues are identical to the first 29 of tesamorelin's backbone.

Sermorelin binds the growth hormone-releasing hormone receptor (GHRHR), a G protein-coupled receptor expressed on somatotroph cells of the anterior pituitary.

Signalling cascade, as described in the literature Receptor engagement activates adenylyl cyclase, converting ATP to cyclic AMP. Rising cAMP activates protein kinase A, which phosphorylates a number of targets including voltage-dependent calcium channels in the cell membrane. Opening of those channels permits calcium influx; the resulting rise in intracellular calcium drives secretory vesicles within the somatotroph to release stored growth hormone.

The distinction that defines the compound class. Sermorelin does not supply exogenous growth hormone. It signals the pituitary to release the endogenous hormone, which means output remains subject to normal physiological feedback — including negative feedback from somatostatin and from IGF-1. Exogenous GH administration bypasses that regulation entirely.

The literature reports that sermorelin's action is relatively specific to GHRHR, without significant alteration of prolactin, insulin, cortisol, glucose, or thyroid hormone levels.

Increased GH secretion raises insulin-like growth factor-1 (IGF-1), which mediates much of the anabolic activity attributed to growth hormone.

Some sources report that sermorelin does not appear subject to tachyphylaxis, and suggest upregulation rather than downregulation of GHRH receptors with repeated exposure. This is a claim from the secondary literature rather than a settled finding.

The original clinical application. Sermorelin was reviewed for use in the diagnosis and treatment of children with idiopathic growth hormone deficiency, with subcutaneous administration at 30 µg/kg reported to increase growth velocity.

(Prakash & Goa, BioDrugs, 1999)

Early work established that pulsatile infusion of an amidated GHRH fragment produced growth in normal and GHRH-deficient rats.

(Clark & Robinson, Nature, 1985)

Single nightly injections of GHRH(1-29) were examined in healthy elderly men.

(Vittone et al., Metabolism, 1997)

A 16-week study in age-advanced men and women reported increases in growth hormone release, IGF-1, lean body mass and skin thickness.

Note that this study used [Nle27]GHRH(1-29)-NH2 — a norleucine- substituted analog at position 27, not sermorelin itself, which carries methionine at that position.

(Khorram, Laughlin & Yen, JCEM, 1997)

GHRH agonists have been examined in models of myocardial infarction, with reported reductions in infarct scar in swine with subacute ischemic cardiomyopathy and effects on fibrosis, apoptosis and cardiac repair pathways.

(Bagno et al., JAHA, 2015; Kanashiro-Takeuchi et al., Oncotarget, 2015)

Interactions between GHRH and GABA-A receptors have been examined in animal models of epilepsy and in tissue from patients with epilepsy.

(Tang et al., Scientific Reports, 2017)

Growth hormone secretion peaks during slow-wave sleep, and the relationship between the GHRH axis and sleep architecture has been examined in both animal and human work, including orexin signalling.

(Shepherd et al., Comp Biochem Physiol, 2007; Zaffanello et al., Frontiers in Endocrinology, 2024)

Effects of GHRH on visceral fat and cardiovascular indices have been reviewed across human studies.

(Stanley & Grinspoon, Growth Hormone IGF Research, 2014)

Growth hormone secretagogues such as GHRP-6 and GHRP-2 act at the ghrelin receptor (GHS-R) rather than GHRHR. Because the two classes engage separate receptors, combined administration has been examined for additive effect, with reported IGF-1 elevations exceeding those from either class alone.

(Sigalos et al., American Journal of Men's Health, 2017)

Reviewed in the context of growth hormone secretagogues and body composition management.

(Sinha et al., Translational Andrology and Urology, 2020)

Sermorelin acetate was formerly marketed in the United States as Geref for pediatric growth hormone deficiency. It is no longer available as a marketed product in the US.

Sermorelin appears on the World Anti-Doping Agency prohibited list. Growth hormone releasing factors are prohibited at all times under the WADA Code, which is relevant to any research context involving competitive athletes.

Material supplied for laboratory use is a research chemical. It is not a drug, food, cosmetic, or dietary supplement as supplied, has not been evaluated by the FDA in that form, and is not intended for human or veterinary use.