Growth Hormone Secretagogues

MK-677 (Ibutamoren)

Also known as Ibutamoren · Ibutamoren mesylate · MK-0677 · L-163191

Emerging researchOralNot FDA-approved for any indication; not lawful as a dietary supplement ingredient in the US and marketed as a research chemical. Prohibited in sport (WADA, growth hormone secretagogues, S2). Long-term safety not established.

MK-677 (ibutamoren) is a non-peptide, orally active growth hormone secretagogue that mimics ghrelin at the GHS-R1a receptor in the hypothalamus and pituitary, producing sustained, non-pulsatile elevation of growth hormone and IGF-1. Unlike the injectable peptides in this category it is taken by mouth. In a long-term randomized trial in older adults it increased fat-free mass but did not improve strength and was associated with worsened insulin sensitivity. It is not an approved medication.

Studied / used for

Studied for sustained elevation of growth hormone and IGF-1
Investigated for fat-free mass and body composition in older adults
Explored for appetite stimulation and in clinical research on muscle wasting

Commonly reported side effects

Increased appetite
Fluid retention and edema
Muscle pain
Increased fasting glucose and reduced insulin sensitivity
Fatigue or drowsiness
Elevated IGF-1

Emerging research. Active research; human evidence still developing. This reflects the strength of the research base, not effectiveness or a recommendation.

Not medical advice.

This is an educational reference. Peptalk does not recommend, prescribe, endorse, or rate any compound, and provides no dosing information. Do not start, stop, or change any peptide, hormone, supplement, or therapy based on this page. All clinical decisions must be made with your licensed healthcare provider.

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