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Home/Growth Hormone, Longevity & Anti-Aging/MK-677 (Ibutamoren)

MK-677 (Ibutamoren)

Oral, non-peptide growth hormone secretagogue (ibutamoren) that activates the ghrelin receptor; studied for GH and IGF-1 elevation.

Overview

MK-677, also known as ibutamoren, is an orally bioavailable, non-peptide agonist of the ghrelin receptor (GHS-R1a) developed by Merck. Although it is grouped with peptides in research catalogs, it is a small molecule. It stimulates growth hormone secretion and raises IGF-1 levels and has been evaluated in randomized trials in older adults, growth hormone-deficient patients, and other populations. It was never approved as a drug, in part because of effects on glucose metabolism seen in long-term studies.

Mechanism

MK-677 mimics ghrelin at the growth hormone secretagogue receptor, amplifying pulsatile GH release from the pituitary and thereby increasing hepatic IGF-1 production. Unlike injectable secretagogue peptides, it is active after oral administration and has a long half-life, producing sustained elevation of GH and IGF-1 with once-daily dosing.

Dosing

Published clinical studies have most often used a once-daily oral dose of 25 mg in adults, with pediatric protocols using weight-based dosing; trials lasted from weeks to over a year. Because the drug is unapproved, any use should follow published research protocols rather than vendor guidance.

Expected Effects

  • sustained increases in circulating GH and IGF-1 in clinical studies
  • increased fat-free mass and decreased fat mass reported in some longer trials in older adults
  • improved sleep quality in some studies, consistent with ghrelin-receptor activity

Side Effects & Tolerability

The most clinically significant finding is a dose- and duration-related increase in fasting glucose and insulin resistance, which limited development. Increased appetite, fluid retention, and elevations in prolactin or cortisol have also been reported. These effects are documented in the published trial literature.

Storage

MK-677 is an oral small molecule; research-grade material should be stored per the supplier label, typically cool, dry, and protected from light, and handled as a powder rather than a reconstituted peptide.

Related peptides

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