GHRP-6

The original growth hormone-releasing hexapeptide, developed by Cyril Bowers' group and first described in Endocrinology in 1984. It was derived from met-enkephalin, with D-amino acids that remove opioid activity.

It binds the ghrelin receptor in the pituitary and hypothalamus, releasing growth hormone through a pathway separate from GHRH; the two together act synergistically. It also activates brain appetite centers and, at higher doses, raises cortisol and prolactin. It binds CD36, which is proposed to explain tissue-protective effects seen in animals.

In 18 normal men, peak growth hormone rose from about 1.2 to about 69 µg/L, with synergy when GHRH was added; cortisol and prolactin roughly doubled only at the highest dose. A Cuban phase I study in 18 healthy men found mild, resolving adverse events in 67%. In rats it strongly increases food intake and reduced stress-induced stomach lesions by about 85%. Heart, brain, gut and liver protection has been shown only in animal models. No human efficacy trials or repeated-use safety data exist.

The phase I study reported sweating (50%), slow heart rate (44%) and sleepiness (17%), all mild with no serious events. FDA cites immunogenicity risk, limited safety data, possible cortisol effects and raised blood sugar from reduced insulin sensitivity. Strong appetite effects are well documented in animals.

Not approved in the US or any other country found. FDA lists it in 503B Category 2 (significant safety risk) since 2023 and 503A Category 3 (insufficient information), so it is not compoundable. WADA prohibits it at all times under S2.4. Status as of October 2026.