OnePin Peptide Library · Growth Hormone
MK-677
Ibutamoren · MK677 · Nutrobal
MK-677 (ibutamoren mesylate) is a non-peptide, orally active growth hormone secretagogue that mimics the action of ghrelin by binding to the growth hormone secretagogue receptor (GHS-R1a). Unlike growth hormone releasing peptides (GHRPs), MK-677 is not a peptide and has excellent oral bioavailability. It stimulates the pituitary gland to release growth hormone (GH) in a pulsatile, physiological pattern, and significantly increases circulating levels of both GH and IGF-1 without suppressing the hypothalamic-pituitary axis.,MK-677 was developed by Merck and investigated in multiple Phase II clinical trials for growth hormone deficiency, muscle wasting, osteoporosis, and age-related frailty. These trials demonstrated consistent and sustained increases in GH and IGF-1 levels (IGF-1 increases of 40-60% above baseline) that persisted with chronic daily dosing for up to 2 years. However, Merck discontinued clinical development and MK-677 was never submitted for FDA approval. It remains an investigational compound.,A critical consideration with MK-677 is its effect on insulin sensitivity and blood glucose. As a ghrelin mimetic, it increases appetite (which is a desired effect for some, but problematic for others) and can worsen insulin resistance, raise fasting glucose, and increase HbA1c. This metabolic trade-off was a significant factor in Merck's decision not to pursue approval and is an important consideration for long-term use. MK-677 also increases cortisol and prolactin in some individuals, though usually within normal ranges.
Oral: Bedtime dosing preferred (GH pulse during sleep, reduces daytime hunger). Take with or without food. Continuous or 5-on-2-off.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
Binds to the ghrelin/growth hormone secretagogue receptor (GHS-R1a) in the hypothalamus and pituitary, mimicking endogenous ghrelin. This stimulates growth hormone-releasing hormone (GHRH) neurons and directly activates pituitary somatotrophs, producing pulsatile GH release that mirrors the natural secretory pattern.,Amplifies GH pulse amplitude without altering pulse frequency, preserving the physiological GH secretion pattern. Also reduces somatostatin (GH-inhibiting hormone) tone, further facilitating GH release. The result is sustained elevation of both GH and IGF-1 levels without the tachyphylaxis seen with continuous GH administration.,As a ghrelin mimetic, MK-677 activates hypothalamic appetite centers (NPY/AgRP neurons), increasing hunger and food intake. It also modulates glucose metabolism through GHS-R1a-mediated effects on pancreatic islets and hepatic glucose output, which can worsen insulin sensitivity.
Binds to the ghrelin/growth hormone secretagogue receptor (GHS-R1a) in the hypothalamus and pituitary, mimicking endogenous ghrelin. This stimulates growth hormone-releasing hormone (GHRH) neurons and directly activates pituitary somatotrophs, producing pulsatile GH release that mirrors the natural secretory pattern.,Amplifies GH pulse amplitude without altering pulse frequency, preserving the physiological GH secretion pattern. Also reduces somatostatin (GH-inhibiting hormone) tone, further facilitating GH release. The result is sustained elevation of both GH and IGF-1 levels without the tachyphylaxis seen with continuous GH administration.,As a ghrelin mimetic, MK-677 activates hypothalamic appetite centers (NPY/AgRP neurons), increasing hunger and food intake. It also modulates glucose metabolism through GHS-R1a-mediated effects on pancreatic islets and hepatic glucose output, which can worsen insulin sensitivity.
What to expect
Days 1-7: Increased appetite and improved sleep quality are the first noticeable effects. Mild water retention begins. GH/IGF-1 elevation starts within 2-3 days.
Evidence
Interactions & stacking
What's safe to combine, and what belongs in a separate pin.
Safe & synergistic
Keep separate
Pharmacokinetics
Storage. Store at room temperature in a cool, dry place. Protect from moisture and light. Oral compound - no reconstitution needed.
Regulatory status
Investigational compound - never FDA-approved. Clinical development discontinued by Merck. Not a dietary supplement. Listed as a prohibited substance by WADA. Classified as a research chemical.
Put it to work
Calculate, log & track
Open MK-677 straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.
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The guide & community
The complete MK-677 walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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