Overview
MK-677 (ibutamoren) is a non-peptide growth hormone secretagogue that mimics the action of ghrelin. Unlike most growth hormone-related compounds, MK-677 is orally active and does not require injection, making it unique in this class of compounds.
Mechanism of Action
MK-677 works by:
- Activating the ghrelin receptor (GHSR) in the brain
- Stimulating growth hormone release from the pituitary
- Increasing IGF-1 levels
- Maintaining elevated GH/IGF-1 without affecting cortisol
Research Findings
Clinical studies have investigated MK-677 for various applications:
- Increased lean body mass in elderly subjects
- Improved bone density markers
- Enhanced sleep quality
- Effects on nitrogen balance
Pharmacokinetics
Key pharmacokinetic properties:
- Oral bioavailability (does not require injection)
- Long half-life allowing once-daily dosing
- Sustained elevation of GH and IGF-1 levels
Side Effects
Reported side effects in clinical trials include:
- Increased appetite (ghrelin-like effect)
- Transient water retention
- Mild joint pain
- Blood glucose elevation in some individuals
Regulatory Status
MK-677 is not FDA-approved and is classified as an investigational drug. It is sometimes categorized with selective androgen receptor modulators (SARMs) despite having a different mechanism. Its use outside of clinical research is not recommended.