Secretagogue

Where the peptide field got the word

Kojima and colleagues open the 1999 ghrelin paper with the usage that still governs this niche. Small synthetic molecules called growth-hormone secretagogues stimulate the release of growth hormone from the pituitary. They act through the growth-hormone secretagogue receptor, a G-protein-coupled receptor. That pathway is distinct from regulation by hypothalamic growth hormone-releasing hormone. [1] PMID: 10604470

The word is older than ghrelin. In 1984 Bowers described a synthetic hexapeptide that specifically elicited a dose-related release of growth hormone in vitro and in vivo, without a concomitant release of LH, FSH, TSH, or prolactin in those experiments. [2] PMID: 6714155 "Specifically" is doing real work. A secretagogue claim is a claim about which hormone moves, not a claim that a peptide is generally stimulating.

Two routes, one loose label

The Kojima abstract draws the line this site should keep. Growth hormone release can be driven by hypothalamic GHRH, and it can be driven by ghrelin acting as the endogenous ligand of the secretagogue receptor. Ghrelin is a 28-amino-acid peptide with an n-octanoyl group on serine 3, and that acylation is required for the activity they measured. [3] PMID: 10604470 Calling both "GH peptides" and stopping there erases the receptor.

Sermorelin Sermorelin growth hormone-releasing hormone (GHRH) analog GHRH analog for endogenous growth hormone stimulation and tesamorelin Tesamorelin growth hormone-releasing hormone (GHRH) analog GHRH analogue studied for visceral fat reduction and GH-axis stimulation are GHRH-family analogues. Ipamorelin Ipamorelin growth hormone secretagogue (GHS) / selective ghrelin receptor agonist Selective growth hormone secretagogue sits on the secretagogue-receptor side of the same conversation. Those are compound pages, not this page. This page exists so a guide can say "secretagogue" and point at a definition instead of implying the word means "any peptide that mentions growth hormone."

What a secretagogue is not

It is not exogenous growth hormone. The pituitary is doing the releasing. It is not proof of a clinical effect in humans just because a rat pituitary released hormone in an incubate. Bowers reported activity in several species and by intravenous, subcutaneous, and intraperitoneal injection in rats. [4] PMID: 6714155 Species, route, and hormone panel still have to be read. A vendor sentence that says "secretagogue" without saying which hormone, which receptor, and which experiment is using the word as marketing.

It is also not a half-life and not a reconstitution instruction. Those are separate entries.

Where the word is already in use here

The growth-hormone secretagogues guide and the GHRH-versus-GHRP guide are the long pages. This entry is the one-sentence meaning they rely on: a releaser of a hormone the gland already makes, and in this literature, usually growth hormone via a path that is not GHRH.