Growth hormone secretagogue binding sites in peripheral human tissues.
Papotti. M M; Ghè. C C; Cassoni. P P; Catapano. F F; Deghenghi. R R; Ghigo. E E; Muccioli. G G
Key Findings
- GHS receptors are most densely present in the human myocardium (heart) and also in adrenal glands, gonads, arteries, lung, liver, skeletal muscle, kidney, pituitary, thyroid, adipose tissue, veins, uterus, skin, and lymph nodes.
- Hexarelin can fully displace a radiolabeled probe from GHS receptors in endocrine tissues, showing higher potency than MK‑0677 or ghrelin.
- In non‑endocrine tissues, only hexarelin (not MK‑0677 or ghrelin) effectively displaces the probe, hinting at a distinct receptor subtype that prefers peptidyl GHS like hexarelin.
- Many tissues (parathyroid, pancreas, placenta, prostate, stomach, colon, etc.) show negligible GHS receptor binding.
Practical Outcomes
- For biohackers, the data suggest that hexarelin may have direct effects on the heart and several metabolic organs, which could be relevant for performance or longevity goals. However, the study provides no dosing, safety, or efficacy information, so it’s not a ready‑to‑use protocol—rather, it highlights areas where further research is needed before self‑experimentation.
Summary
The study mapped where the body’s growth‑hormone‑secretagogue (GHS) receptors are located and found they’re especially abundant in the heart and also show up in many other organs like the adrenal glands, muscles, liver and fat. Hexarelin, a peptide GHS, binds strongly to these receptors, more so than the similar drug MK‑0677 or the natural hormone ghrelin, especially in endocrine (hormone‑producing) tissues.
Abstract
The family of GH secretagogues (GHS) includes peptidyl (hexarelin) and nonpeptidyl (MK 0677) molecules possessing specific receptors in the brain, pituitary, and thyroid. GHS receptor subtypes have also been identified in the heart; and a gastric-derived peptide, named ghrelin, has recently been proposed as a natural ligand. Our aim was to investigate the presence of GHS receptors in a wide range of human tissues, by radioreceptor assay with [125I]Tyr-Ala-hexarelin. GHS receptors were detected mainly in the myocardium, but they were also present (in order of decreasing binding activity) in adrenal, gonads, arteries, lung, liver, skeletal muscle, kidney, pituitary, thyroid, adipose tissue, veins, uterus, skin, and lymphnode. In contrast, negligible binding was found in parathyroid, pancreas, placenta, mammary gland, prostate, salivary gland, stomach, colon, and spleen. Hexarelin, MK 0677, and human ghrelin completely displaced the radioligand from binding sites of endocrine tissues, but MK 0677 and ghrelin were less potent than hexarelin. In nonendocrine tissues, both MK 0677 and ghrelin were inactive in displacement of [125I]Tyr-Ala-hexarelin, whereas hexarelin was as active as a displacing agent in endocrine tissues. This study provides the first detailed analysis of the tissue localization of GHS receptors and suggests that a still unknown receptor subtype, specific for peptidyl GHS, may exist in the heart and in other tissues.
Study Information
pubmed
2000
10.1210/jcem.85.10.6846