Growth hormone-releasing hormone runs 44 amino acids long. Decades ago, though, researchers found that its first 29 carry almost the entire message — and that opening segment is sermorelin, written formally as GHRH(1-29). This article is provided for research use only and looks at the chemistry of that fragment: what it is, where it comes from, how it talks to its receptor, and why it disappears from plasma so fast. One caveat up front. Sermorelin is also an international nonproprietary drug name, and research-grade material is not equivalent to the FDA-approved pharmaceutical product of the same name.
What Sermorelin Actually Is
In one line: sermorelin is the 29-amino-acid front end of growth hormone-releasing hormone, reproduced as a standalone peptide. Its chemical profile gives the molecular formula C149H246N44O42S, a molar mass of roughly 3,357.93 g/mol, and the CAS number 86168-78-7. Its tail is capped with an amide group rather than a free acid — a small structural detail that turns out to matter for how the molecule is recognized.
One well-documented fact is what makes the fragment interesting: it's described as the shortest fully functional fragment of GHRH. Throw away more than a third of the parent hormone, in other words, and the remaining piece still behaves in laboratory models like the whole thing. The rest of this article is really an answer to one question — how can such a large molecule be trimmed so aggressively and still work?
Where the Fragment Comes From
To understand the fragment, start with the parent. Growth hormone-releasing hormone, as its reference entry describes, is a 44-residue peptide made in the arcuate nucleus of the hypothalamus. It's released in pulses and travels through the hypothalamo-hypophyseal portal system — a short, dedicated set of blood vessels — to the anterior pituitary, where it prompts the release of growth hormone.
The trimming story goes back to the early 1980s. Work by Wehrenberg and Ling showed that the first 29 residues of GHRH were as potent in laboratory models as the full 44-residue chain. That result gave the fragment its working name, GRF(1-29), and later its nonproprietary name, sermorelin. If you're researching this compound, that finding is the historical hinge: it established that the "active core" of the hormone lives near the N-terminus rather than spread across the whole sequence.
Reading the 29-Residue Sequence
Here's the chain, residue by residue: 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. Line it up against the parent hormone and you'll see it's an exact copy of GHRH's opening 29 amino acids, as the analogue literature lays out.
A couple of reading conventions help here. Residues are numbered from the N-terminus, so "position 2" means the second amino acid — an alanine — and the "1-29" label simply means residues one through twenty-nine. That trailing "NH2" is the amide cap mentioned earlier. Thinking structurally rather than by name is a habit worth keeping across peptide chemistry; the same approach applies when you study other short, defined peptide sequences where the exact residue order is the whole story.