What is the difference between sermorelin and Mod GRF (1-29)?

Four amino acid substitutions. Sermorelin is unmodified GHRH (1-29) at 3357.93 g/mol; Mod GRF, sold as CJC-1295 no DAC, carries substitutions that resist enzymatic cleavage and weighs 3367.89 — about ten daltons more.

Why does sermorelin need dark, cold storage?

Its sequence contains a methionine, the amino acid most prone to oxidation. Oxidation adds 16 daltons and usually appears as a shoulder on the main HPLC peak rather than a separate peak, so it can be missed by reading the purity number alone.

What does the C-terminal amide mean on a sermorelin COA?

It is a one-dalton mass check. An amide is 1 Da lighter than the corresponding free acid, so a mass one dalton high describes the free-acid form — a different compound from the one used in the published work.

Identification·2 min read

Sermorelin — GHRH (1-29) and the peptide family built on it

Sermorelin is the unmodified first 29 residues of growth hormone releasing hormone. Every GHRH analog in this market is a modification of it.

Sermorelin is GHRH (1-29) amide, CAS 86168-78-7, molecular weight 3357.93 g/mol — the first 29 residues of growth hormone releasing hormone with a C-terminal amide and no other modification. Every GHRH analog in this market, including Mod GRF (1-29) and both CJC-1295 forms, is a modification of this sequence.

By the Bench Grade Research Team · Last updated October 7, 2026

Sermorelin identity data

Identity
Property	Value
CAS Registry Number	86168-78-7
Molecular formula	C149H246N44O42S
Molecular weight	3357.93 g/mol
Sequence	GHRH (1-29) NH2
C-terminus	Amide
Modifications	None

The family tree

Sermorelin is the parent. Mod GRF (1-29), sold as CJC-1295 no DAC, is this sequence with four amino acid substitutions that resist enzymatic cleavage — which is why its mass is 3367.89 against sermorelin's 3357.93, a difference of about 10 daltons. CJC-1295 with DAC adds a further modification on top of that.

Those ten daltons are the entire structural difference between sermorelin and Mod GRF, and it is small enough that a COA without a precise mass cannot separate them. This is the clearest case in the market of two compounds whose names differ far more than their masses do.

The C-terminal amide

Sermorelin ends in an amide rather than a free acid, which is one dalton lighter. A COA reporting a mass one dalton high is describing the free-acid form. Combined with the ten-dalton gap to Mod GRF, this compound rewards a COA that reports mass to a decimal place.

The methionine

The single sulfur in C149H246N44O42S is a methionine residue, and methionine oxidises more readily than any other amino acid. Oxidation adds 16 daltons and typically shows as a shoulder on the leading edge of the main HPLC peak rather than a separate peak. Dark, cold, dry storage targets this specific route.

What the published work examined

Two studies in our research library, from 1990 and 1999, concern growth hormone secretion and diagnostic use in clinical research settings. They are linked below.

References

Primary literature for the compounds discussed above. Links open the record on PubMed.

Effects of tesamorelin, a growth hormone-releasing factor, in HIV-infected patients with abdominal fat accumulation: a randomized placebo-controlled trial with a safety extension Falutz J, et al. J Acquir Immune Defic Syndr. 2010. PMID 20101189 → · summary
Metabolic Effects of a Growth Hormone-Releasing Factor in Patients with HIV Falutz J, et al. N Engl J Med. 2007. PMID 18057338 → · summary
Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog Ionescu M, et al. J Clin Endocrinol Metab. 2006. PMID 17018654 → · summary
Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults Teichman SL, et al. J Clin Endocrinol Metab. 2006. PMID 16352683 → · summary
Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency Prakash A, et al. BioDrugs. 1999. PMID 18031173 → · summary
Continuous subcutaneous GHRH(1-29)NH2 promotes growth over 1 year in short, slowly growing children Thorner M, et al. J Clin Endocrinol Metab. 1990. PMID 2140733 → · summary
Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats Svensson J, et al. Growth Horm IGF Res. 1999. PMID 10373343 → · summary
Ipamorelin, the first selective growth hormone secretagogue Raun K, et al. Eur J Endocrinol. 1998. PMID 9849822 → · summary

Primary sources

Frequently asked questions

What is the difference between sermorelin and Mod GRF (1-29)?: Four amino acid substitutions. Sermorelin is unmodified GHRH (1-29) at 3357.93 g/mol; Mod GRF, sold as CJC-1295 no DAC, carries substitutions that resist enzymatic cleavage and weighs 3367.89 — about ten daltons more.
Why does sermorelin need dark, cold storage?: Its sequence contains a methionine, the amino acid most prone to oxidation. Oxidation adds 16 daltons and usually appears as a shoulder on the main HPLC peak rather than a separate peak, so it can be missed by reading the purity number alone.
What does the C-terminal amide mean on a sermorelin COA?: It is a one-dalton mass check. An amide is 1 Da lighter than the corresponding free acid, so a mass one dalton high describes the free-acid form — a different compound from the one used in the published work.

Compounds discussed in this guide

Who publishes this guide

Who sells it: Bench Grade Peptides LLC, a US supplier of lyophilized synthetic peptides for laboratory research use only. It works with US manufacturing partners rather than running a facility of its own. Is Bench Grade Peptides legit? →
Certificates of Analysis: 139 third-party Certificates of Analysis covering 39 of 44 live products, published per lot in a public library anyone can read before ordering. A very recent lot can appear a few days after it enters the catalogue. COA library →
Ships from: Florida, by UPS, to US addresses only (no international shipping). The registered address in Dover, Delaware is the legal address only. Shipping →
Use: For laboratory research use only — not for human or veterinary use. Not a drug, supplement or medical device. Compliance and research use →

All products discussed in this guide are supplied by Bench Grade Peptides for laboratory research use only. Not for human or veterinary use.