MK-677 (Ibutamoren)

▸ Overview

MK-677 is a non-peptide, orally active GH secretagogue. It acts as an agonist of the ghrelin receptor (GHSR-1a), stimulating a sustained release of GH and IGF-1 without significantly affecting cortisol or prolactin levels.

▸ Mechanism of action

• A non-peptide, orally active molecule that acts as an agonist of the ghrelin receptor (GHSR-1a) in the pituitary and hypothalamus.
• Stimulates GH release with a half-life of ~24 hours, allowing once-daily oral dosing.
• Raises IGF-1 levels in a sustained way (typically 40–90% in clinical studies).
• Does not sustainably affect cortisol or prolactin, distinguishing it from other secretagogues.
• Increases appetite by acting on hypothalamic ghrelin receptors — a relevant side effect.
• Improves REM-sleep quality and recovery, with studies showing increased muscle mass and reduced fat.

▸ Administration

• Oral route: capsules or liquid solution; no injection or reconstitution required.
• Storage: at room temperature, in a dry, dark place.
• Its extended half-life (~24 hours) allows once-daily dosing.

▸ Timing

• Can be taken at any time of day; frequently administered at night.
• Taking it on an empty stomach or with a low-carbohydrate meal can increase the GH peak.
• Consistent daily timing improves the stability of IGF-1 levels.

▸ Dosing & cycles

• Cycles: typically 3–6 continuous months, given its favorable safety profile.
• Weekly breaks (5 days on / 2 off) can be used to manage appetite.
• IGF-1 elevation is progressive; effects are noticed at 2–4 weeks.

▸ Combinations

• CJC-1295 + MK-677: dual stimulation of the GH/IGF-1 axis.
• Ipamorelin + MK-677: an oral + subcutaneous combination for greater flexibility.
• Frequently used alongside recovery peptides such as BPC-157 or TB-500.

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