Hexarelin common uses, half-life, side effects and more

Hexarelin is a synthetic growth hormone releasing peptide. It makes the pituitary release its own growth hormone. It is GHRP-6 with one extra methyl group added to help it survive digestion. It releases more growth hormone than GHRP-6 does. No source establishes by how much. It reached phase 2 trials for growth hormone deficiency and was discontinued there. No regulator anywhere has ever reviewed it. It also binds a second receptor found on heart and immune cells. That is unusual for this family and is why it turns up in cardiovascular research.

• Raising growth hormone without injecting growth hormone itself
• Recovery and body composition (community use)
• Short cycles chosen because the response fades
• Appetite stimulation
• Historical testing for growth hormone deficiency

Once or twice daily in community practice

Community practice is 100 to 200 mcg under the skin once or twice a day. That figure comes from forum protocols catalogued in a review. The longest published trial happens to land in the same place, at 1.5 mcg per kg under the skin twice a day for 16 weeks. Other published work used single doses into a vein at 0.5 to 2 mcg per kg. Children in the growth studies were given 60 mcg per kg by nose three times a day. The commonly quoted cycle of a few weeks on and several weeks off matches no source. The one catalogued community cycle runs 8 to 12 weeks on and 4 weeks off. The growth hormone response is down about a third after one week of twice-daily dosing and down about 45 percent by 16 weeks. It returns to baseline four weeks after stopping.

No human study has measured how long hexarelin itself lasts in the blood. The widely quoted 55 minutes is not the peptide's half-life. It is how fast the growth hormone response fades. That same sentence also gives the 30 minute peak and the 240 minute return to baseline. Measured half-lives exist only in animals at about two hours in dogs and about 76 minutes in rats. A review that reports a bare half-life for hexarelin is quoting the rat figure without saying so.

• A rise in cortisol, ACTH, and prolactin after a single dose
• The cortisol and ACTH response fades with repeated dosing before the growth hormone response does
• Less deep sleep when dosed in the evening
• Increased appetite in rodent studies
• No side effects were reported in the published human courses given by nose or by mouth

Hexarelin activates the ghrelin receptor on the pituitary and releases the body's own growth hormone. That raises IGF-1 from the liver. It also binds a scavenger receptor called CD36 on heart cells, blood vessel lining, and immune cells. The two receptors do different jobs. The short-lived boost in heart contraction runs through the ghrelin receptor rather than through CD36. What CD36 does in the heart is narrow the coronary arteries. The researchers who found that proposed it as a possible mechanism for coronary spasm rather than as a benefit. CD36 also drives cholesterol handling in immune cells. That work was done in cell culture and mice rather than in hearts.

Hexarelin reached phase 2 for growth hormone deficiency and was discontinued. It was never tested in phase 3 and no regulator has reviewed it. The human record is a set of small short studies of hormone release. The longest ran 16 weeks in 12 elderly adults. The most-cited finding from that work is the fading growth hormone response. A small program gave it by nose to short children for several months and growth speeded up. Those studies had no control group and never reported adult height. A blood marker of heart risk doubled in those same children and insulin rose more than threefold. No human study has ever measured a heart outcome.

• It is banned in sport at all times and is named individually on the prohibited list
• Its effect on coronary arteries in laboratory hearts was narrowing rather than widening and was proposed as a mechanism for coronary spasm
• Children given it by nose for several months had a doubling of a blood marker of heart risk and a large rise in insulin
• Mouse studies covering pregnancy found fewer successful pregnancies and impaired memory in the offspring
• Growth hormone and IGF-1 drive cell growth so it is not for anyone with a current or past cancer