It is produced in the hypothalamus, the pancreas and the gut, and exists in two main forms of 14 and 28 amino acids. It acts on five receptors (SSTR1 to SSTR5) and its overall effect is inhibitory: it reduces the secretion of growth hormone, TSH, insulin, glucagon and several digestive hormones.
In the growth hormone axis, somatostatin and GHRH work in opposition. When somatostatin falls and GHRH rises, the pituitary releases a pulse of GH; when they reverse, secretion stops. That alternation is what gives GH its pulsatile pattern.
That is why secretagogues that counteract somatostatin tone (ghrelin mimetics such as ipamorelin) enhance the response to GHRH. And that is why GH itself and IGF-1, by increasing somatostatin, hold back their own production.
Somatostatin explains why the response to a GHRH analogue on its own is limited and why its combination with a GHRP is studied so much.
Related terms
Learn it in depth at the Peptide University
- Physiology of the GH/IGF-1 axis · Module 5
- GHRPs, ghrelin mimetics and synergy · Module 5
- IGF-1, its binding proteins and its variants · Module 5
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Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).