MK-677

What is MK-677?

An orally active growth hormone secretagogue that mimics ghrelin to stimulate sustained GH and IGF-1 release. Technically a non-peptide small molecule, but commonly grouped with GH peptides due to its mechanism.

MK-677 has been studied in several clinical trials, including a 12-month randomized controlled trial in adults aged 60-81 that showed increases in GH and IGF-1 to young-adult levels and gains in fat-free mass. However, it did not improve strength or function in that trial, and some lean mass gains may reflect intracellular water retention. A separate trial in heart failure patients was stopped early due to safety concerns. The FDA has flagged it as posing significant safety risks and it remains unapproved.

Benefits & evidence

How it works

MK-677 is a non-peptide agonist of the ghrelin receptor (GHS-R1a). By mimicking ghrelin, it signals the pituitary to release growth hormone in a pulsatile fashion. Unlike injectable GH secretagogues, it is orally bioavailable, which makes it convenient but also means it produces more sustained ghrelin receptor activation.

This sustained activation raises GH and IGF-1 levels over a 24-hour period but also stimulates appetite (a natural ghrelin effect) and can increase fasting glucose and reduce insulin sensitivity. It does not significantly suppress the body's own GH production, and its effects on GH persist for months without tachyphylaxis.

Dosing information

Side effects

Most side effects tend to improve as your body adjusts.

Research (10 studies)