MK-677 (Ibutamoren)

Typical use cases

Dosing guidelines

Titration

Community protocols commonly describe starting at a lower dose (e.g., 10 mg) and observing tolerance for appetite, water retention, and lethargy before any adjustment; many report dosing at night because of GH pulse timing and sleepiness, while others prefer morning to limit sleep disruption. Educational only — not a dosing recommendation.

Reconstitution

N/A — orally administered (capsules or oral liquid); no reconstitution required

Injection sites

N/A — oral administration (swallowed capsule or liquid)

Storage & handling

Commonly stored in a cool, dry place away from light and humidity; oral liquid preparations are often refrigerated and capsules kept at room temperature per product labeling

Side effects

• Increased appetite Mild · Common
• Fluid retention / edema Mild · Common
• Lethargy, drowsiness, or fatigue Mild · Common
• Elevated fasting blood glucose / reduced insulin sensitivity Moderate · Common
• Muscle or joint pain (arthralgia/myalgia) Mild · Uncommon
• Numbness or tingling (transient paresthesia) Mild · Uncommon

Research summary

MK-677 is one of the most extensively studied oral growth hormone secretagogues, with human data spanning healthy volunteers, older adults, and disease populations. It is a non-peptide spiroindoline agonist of the ghrelin receptor (GHS-R1a) that signals through the Gq/PLC/IP3 pathway in pituitary somatotrophs to amplify pulsatile GH release, secondarily raising IGF-1. Randomized trials have shown it can restore GH/IGF-1 toward young-adult levels in older adults and reverse short-term diet-induced nitrogen wasting (Murphy et al., 1998). In a 12-month randomized trial, Nass et al. (2008, Annals of Internal Medicine) reported that 25 mg/day increased fat-free mass by roughly 1.1 kg in healthy older adults (about a 1.6 kg difference versus placebo, which lost mass), but this did not translate into measured gains in strength or function. A large 12-month Alzheimer's trial (Sevigny et al., 2008, Neurology) confirmed robust IGF-1 elevation (~73% at one year) yet found no slowing of cognitive decline, illustrating that target engagement does not guarantee clinical benefit. Reported effects on bone turnover markers and sleep architecture (increased slow-wave and REM sleep) are described but less consistently translated into hard outcomes. The chief and recurring safety signals across trials are increased appetite, fluid retention/edema, and impaired glucose tolerance with elevated fasting glucose and reduced insulin sensitivity. Limitations include modest functional benefits, the glucose-metabolism concern, and the fact that MK-677 has never received regulatory approval for human therapeutic use; it is discussed as a research compound rather than an approved medicine.

Key references

• https://pubmed.ncbi.nlm.nih.gov/9467534/
• https://pubmed.ncbi.nlm.nih.gov/18981485/
• https://pubmed.ncbi.nlm.nih.gov/19015485/
• https://pmc.ncbi.nlm.nih.gov/articles/PMC5632578/
• https://pubchem.ncbi.nlm.nih.gov/compound/Ibutamoren

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