Sermorelin and Mod GRF 1-29 are two analogues of GHRH, the hormone that tells the pituitary to release growth hormone. Sermorelin is the older one: an exact copy of the active fragment of GHRH, sold for years as the approved medicine Geref. Mod GRF 1-29 is the same sequence with four substituted amino acids that make it last longer. At the receptor both do the same thing; what separates them is stability in the body and regulatory history. Neither is an approved preparation today, and both are banned in sport all year round.
What is a GHRH analogue?
A GHRH analogue is a synthetic peptide that imitates growth hormone releasing hormone. Natural GHRH carries its active part in the first 29 amino acids of the chain. That part binds the GHRH receptor in the anterior pituitary and triggers a release of growth hormone. An analogue copies that fragment, or alters it so that it survives longer in the blood. This whole group of peptides works indirectly, through your own pituitary, rather than by supplying growth hormone from outside. The mechanism of the group is described in the article on growth hormone peptides.
What is sermorelin?
Sermorelin is a shortened and amidated version of human GHRH, 29 amino acids long. Its sequence matches the natural 1-29 fragment with no substitutions. Merck Serono sold it as Geref: from 1990 at a dose of 0.05 mg for an intravenous diagnostic test, and from 1997 at 0.5 to 1 mg for subcutaneous treatment of children with growth hormone deficiency. The manufacturer later withdrew the preparation and surrendered the authorisation for manufacturing and commercial reasons unrelated to safety or efficacy. Sermorelin is now available only as research material.
Sermorelin has a very short half-life, on the order of ten minutes. After an injection it therefore produces a single short burst of growth hormone and disappears quickly from the blood.
What is Mod GRF 1-29?
Mod GRF 1-29 is sermorelin with four substituted amino acids. The most important substitution is at position two, where natural L-alanine is replaced by D-alanine. That change blocks the enzyme dipeptidyl peptidase-4, which normally cuts the peptide from the start of the chain. The result is a half-life of about thirty minutes, roughly three times longer than sermorelin’s. The GHRH receptor is stimulated in the same way. The compound has no authorisation for any use and remains a substance in development.
Mod GRF 1-29 and “CJC-1295 without DAC” are two names for the same compound. Shops sometimes list them as separate items, but the molecule is identical.
Sermorelin or Mod GRF 1-29: what separates them in practice?
| Feature | Sermorelin | Mod GRF 1-29 (CJC-1295 without DAC) |
|---|---|---|
| Sequence | natural GHRH fragment 1-29 | fragment 1-29 with 4 substitutions |
| Key change | none | D-alanine at position 2, resistance to DPP-4 |
| Half-life | about 10 minutes | about 30 minutes |
| Regulatory history | Geref, FDA from 1990 and 1997 | never authorised |
| Status today | research material | research material |
Pharmacologically these two peptides sit close together. Both give a short, pulsatile release of growth hormone, and Mod GRF 1-29 holds the signal a little longer after a single dose. The larger difference lies in their history: sermorelin was a real medicine with decades of human data, while Mod GRF 1-29 never went through authorisation.
And where does CJC-1295 with DAC fit in?
CJC-1295 with DAC is a third molecule with a different profile. DAC stands for a complex that binds the drug to plasma proteins. Because of it the half-life rises to about eight days and one injection a week is enough. Instead of short pulses the peptide then gives steady, stretched-out stimulation of the GHRH receptor. The difference between the version with DAC and the one without is taken apart in a separate article on CJC-1295 with or without DAC.
What is the legal and sporting status of these peptides?
Neither sermorelin nor Mod GRF 1-29 is a medicine you can buy in a pharmacy. Both are substances intended for laboratory research, with no authorisation as a medicinal product. On the WADA prohibited list they appear under section S2.2.4, which covers growth hormone releasing hormone and its analogues, named explicitly alongside CJC-1295, tesamorelin and others. The ban applies all year, in and out of competition. The full picture is set out on the legal warning page and in the article on the legal status of peptides. Both molecules are stocked as research material: sermorelin and Mod GRF 1-29.
Frequently asked questions
What is the difference between sermorelin and Mod GRF 1-29?
Sermorelin is an exact copy of the active GHRH fragment. Mod GRF 1-29 is the same sequence with four substituted amino acids that extend the action from about ten to about thirty minutes. At the GHRH receptor both act the same way.
Are Mod GRF 1-29 and CJC-1295 without DAC the same thing?
Yes. They are two names for one compound, the GHRH fragment 1-29 with substitutions that resist the enzyme DPP-4. Listings sometimes separate them, but the molecule is the same.
Is sermorelin a medicine?
It was. As Geref it held FDA approval from 1990 for a diagnostic test and from 1997 for treating children with growth hormone deficiency. The manufacturer withdrew it for commercial reasons, not safety ones. Today sermorelin is a research substance.
Which of these peptides lasts longer?
Mod GRF 1-29, with a half-life of about thirty minutes against about ten minutes for sermorelin. CJC-1295 with DAC lasts about eight days, but gives steady stimulation rather than short pulses.
Can they be used in sport?
No. GHRH analogues are on the WADA prohibited list under section S2.2.4 and are banned all year, in and out of competition.
Where this information comes from
The sequence and amidation of sermorelin, the Geref authorisation dates of 1990 and 1997 with their doses, and the reason for withdrawal come from the FDA record for that preparation. The D-alanine substitution at position two, the resistance to DPP-4 and the half-life of about thirty minutes come from the published chemistry of Mod GRF 1-29. The section S2.2.4 listing comes from the WADA prohibited list. These sources were checked on 6 September 2026.