GHRP-6 is a synthetic hexapeptide and one of the earliest growth hormone secretagogues, predating the discovery of ghrelin itself. It was instrumental in identifying the ghrelin receptor.

As a research tool it is historically important. As something to administer, it is largely superseded by more selective agents, and its defining practical characteristic is that it does several things at once rather than one thing cleanly.

Agonist at the growth hormone secretagogue receptor GHS-R1a, the ghrelin receptor, producing pulsatile GH release from the pituitary.

Unlike ipamorelin, it is not selective. Doses that release GH also raise cortisol and prolactin, and it strongly stimulates appetite through the same receptor. It also produces tachyphylaxis: the GH response attenuates with repeated administration.

Early clinical, mostly pharmacodynamic. Human studies from the 1990s established that it raises GH in a dose-dependent way, alongside cortisol and prolactin.

There is no adequately powered evidence for any clinical outcome. It was investigated as a GH secretagogue and did not progress to an approved indication.

For body composition or recovery in healthy adults there is no controlled human evidence at all, and the pharmacodynamic tachyphylaxis is a specific reason to be sceptical of extrapolating single-dose GH data to sustained use.

Reported effects in short human studies include intense hunger, flushing, and transient increases in cortisol and prolactin. Sustained prolactin elevation has its own endocrine consequences.

No long-term safety data. The concerns are those of GH/IGF-1 elevation plus the added complication of a non-selective endocrine response. Prohibited in sport under WADA's S2 category.

Never approved. Sold as a research chemical, prohibited in sport, and not manufactured to pharmaceutical standards outside a research setting.