Oral, once-daily growth hormone secretagogue. Technically a small molecule, not a peptide — but lumped into the category for protocol purposes.
MK-677 (also known as ibutamoren, mibutamoren, or Nutrobal) is a small molecule that mimics the action of ghrelin at the ghrelin receptor (GHSR-1a) in the pituitary and hypothalamus. Despite being grouped with "peptides" in common use, it is technically not a peptide — it's a small molecule with full oral bioavailability, which makes it distinctive in this category. A typical dose is once-daily oral, most often at bedtime.
Because it stimulates natural pulsatile GH release, MK-677 produces sustained elevation of both growth hormone and IGF-1, comparable to what tesamorelin produces via the GHRH pathway. Unlike injectable GHRH analogs, however, MK-677 also triggers endogenous ghrelin effects — increased appetite, measurable water retention, and some users experience transient elevation of cortisol and prolactin.
MK-677 is one of the compounds where careful biomarker tracking genuinely matters. It can modestly impair glucose tolerance in some users, which only shows up on fasting glucose and fasting insulin panels — not on weight or subjective measures. Anyone running it should pull these at baseline and 8-week marks at minimum.
MK-677 activates the growth hormone secretagogue receptor (GHSR-1a), the endogenous receptor for ghrelin. This stimulates pulsatile endogenous GH release from the pituitary, increases IGF-1 production from the liver, and produces ghrelin-associated effects like increased appetite. Unlike GHRH analogs (tesamorelin, sermorelin), MK-677 acts further upstream and produces a broader endocrine effect — including the appetite and water-retention signals that come with ghrelin stimulation.
Standard dose is 25 mg oral once daily, typically at bedtime (many users find the compound makes them drowsy). Some users run 10 mg to minimize water retention and appetite effects. Cycles typically run 2–6 months, often with structured off-periods. Baseline IGF-1 is drawn before starting; response is assessed at the 4–8 week mark. Fasting glucose and insulin should be monitored — MK-677 is the peptide category compound most associated with insulin resistance in practical use.
Education only — not medical advice. Any protocol change should involve your licensed provider.
When running MK-677, these are the biomarkers most commonly tracked to assess response and safety:
Free calculator for MK-677 reconstitution math — vial size, BAC water volume, and exact syringe units.
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