What Is Sermorelin? GHRH (1-29) Peptide Profile

Cover illustration: AI-generated editorial artwork. Conceptual only; not an exact molecular structure, actual laboratory result or evidence of clinical effects.

Sermorelin is GHRH (1-29)-NH2: the first 29 amino acids of human growth hormone-releasing hormone, with an amidated C-terminus. Among the compounds in this category it is unusual in having a peer-reviewed human literature stretching back to the mid-1980s.

For laboratory research use only. The research materials supplied by HealthyWelness are not approved medicines, foods or cosmetics and are not for human or veterinary use. This article summarises published research and is not medical advice.

Key points

Sequence: residues 1–29 of human GHRH, C-terminally amidated.
Receptor: the GHRH receptor (GHRHR), a class B GPCR on pituitary somatotrophs.
Not a ghrelin receptor ligand — that is the GHRP family.
Literature: human studies published from 1985 onward.
Short acting relative to modified analogues, by design rather than by deficiency.

Why 29 residues

Native GHRH is a 44-amino-acid peptide. Classic structure-activity work truncated it from the C-terminus and asked at what point receptor activity was lost. The answer was residue 29: the 1–29 fragment retained the activity of the full-length hormone, while shorter fragments did not. C-terminal amidation was added because the free acid form is less potent.

This is a textbook illustration of a general principle in peptide pharmacology: the receptor-binding information is often carried by a subdomain, not the whole molecule. The remaining 15 residues of GHRH are not inert in a biological sense, but they are not required for receptor activation.

The 1980s human studies

Barron and colleagues (1985) compared GHRH (1-29)-NH2 with a D-Ala2 analogue in normal men. That paper is worth knowing about for two reasons. First, it establishes that the fragment is active in humans, not only in vitro. Second, the comparison with a D-amino-acid-substituted analogue in the same study is effectively the opening move of the entire modified-GHRH-analogue research programme that later produced compounds such as CJC-1295. Position 2 is the site of DPP-4 cleavage; substituting a D-amino acid there was the first widely used way to slow degradation.

Study	Year	Subject
Barron et al., Peptides	1985	GH response to GHRH (1-29)-NH2 vs a D-Ala2 analogue in normal men
Neyzi et al., Acta Paediatr Suppl	1993	Growth response to GHRH (1-29)-NH2 compared with growth hormone
Khorram et al., JCEM	1997	Immune system measures following [Nle27]GHRH (1-29)-NH2 in older adults

The 1993 comparison with growth hormone itself is the conceptually interesting one, because it contrasts two different pharmacological strategies: supplying the downstream hormone directly, or acting one step upstream at the releasing-hormone receptor. The two approaches differ in whether pituitary feedback regulation remains in the loop. That distinction, rather than any potency ranking, is the reason the GHRH-analogue class continued to be studied after recombinant GH became available.

Degradation, and why that is informative

Sermorelin is cleaved rapidly in plasma, with dipeptidyl peptidase-4 acting at the N-terminus a principal route. Every subsequent modification in this family — D-amino acid substitutions, the Nle27 change seen in Khorram et al., the albumin-binding chemistry of CJC-1295 — is an answer to that problem.

So the short half-life makes sermorelin the useful reference point in comparative work. When a paper reports that a modified analogue has an extended profile, sermorelin is usually what it is extended relative to. See sermorelin compared with CJC-1295 for how that comparison is set up.

Handling in the lab

Supplied lyophilized; keep the sealed vial at −20 °C, protected from light and moisture.
Reconstitute gently — direct the diluent down the vial wall and swirl; do not shake a 29-residue peptide into foam.
Aliquot after reconstitution. Repeated freeze–thaw is a documented cause of peptide loss.
Keep working solutions at 2–8 °C and use within the window on the data sheet. See storing reconstituted peptides.
Note that protease activity in a biological sample will act on this peptide quickly; include inhibitors where the assay allows.
Concentration maths: peptide reconstitution calculator.

Our sermorelin research material ships with HPLC purity and MS identity data per lot.

Open questions

How do pulsatile and continuous receptor exposure differ in their downstream transcriptional effects?
What is the practical consequence of retaining versus bypassing pituitary feedback regulation?
Do the GHRH receptor populations reported outside the pituitary respond to the 1–29 fragment in the same way?

Sermorelin compared with CJC-1295
Sermorelin, ipamorelin and tesamorelin compared
GHRP-2 compared with GHRP-6

Frequently asked questions

What is sermorelin?

Sermorelin is a synthetic 29-amino-acid peptide corresponding to residues 1 to 29 of human growth hormone-releasing hormone, with a C-terminal amide. It is the shortest N-terminal fragment of GHRH reported to retain full activity at the GHRH receptor.

Why is it written as GHRH (1-29)?

Native GHRH is 44 amino acids long. Structure-activity work established that the first 29 residues carry the receptor-activating information, so the fragment is designated GHRH (1-29). The NH2 suffix seen in the literature indicates C-terminal amidation.

How does sermorelin differ from a GHRP?

Sermorelin acts at the GHRH receptor. The growth hormone-releasing peptides, such as GHRP-2 and GHRP-6, act at the ghrelin receptor (GHS-R1a). They are two separate receptor systems that converge on the same pituitary cells.

Is sermorelin a new compound?

No. Human studies with GHRH (1-29)-NH2 were published in the mid-1980s, making it one of the longest-studied peptides in this class.

What is the difference between sermorelin and CJC-1295?

Both act at the GHRH receptor. CJC-1295 is a modified GHRH analogue carrying substitutions that increase resistance to enzymatic degradation; sermorelin is the unmodified 1-29 fragment and is degraded more rapidly.

References

Barron JL, et al. Growth hormone responses to growth hormone-releasing hormone (1-29)-NH2 and a D-Ala2 analog in normal men. Peptides. 1985. PMID: 2866496 https://pubmed.ncbi.nlm.nih.gov/2866496/
Khorram O, et al. Effects of [norleucine27]growth hormone-releasing hormone (GHRH) (1-29)-NH2 administration on the immune system of aging men and women. J Clin Endocrinol Metab. 1997. PMID: 9360512 https://pubmed.ncbi.nlm.nih.gov/9360512/
Neyzi O, et al. Growth response to growth hormone-releasing hormone(1-29)-NH2 compared with growth hormone. Acta Paediatr Suppl. 1993. PMID: 8329826 https://pubmed.ncbi.nlm.nih.gov/8329826/