Oral non-peptide ghrelin mimic that raises GH and IGF-1 for 24 hours. Not approved; in Phase 3 for children with GH deficiency.
Also called Ibutamoren, Ibutamoren mesylate, MK-0677, L-163,191, LUM-201
MK-677 is not a peptide. It is a small spiro-piperidine molecule Merck designed in the early 1990s to do what GHRP-6 does, switch on the ghrelin receptor, but as a once-daily pill. It is included here because it is sold and discussed alongside the GH-releasing peptides. A 25 mg daily dose roughly doubled 24-hour GH in older adults and pushed IGF-1 up by 40 to 90 percent into the range of young adults, and the effect held for up to two years.
Merck ran it through real randomized trials. In 65 healthy adults aged 60 to 81, a year of 25 mg a day added about 1.1 kg of lean mass while the placebo group lost 0.5 kg, but strength and physical function did not improve, and the extra weight included more limb fat. In 563 people with Alzheimer's disease it raised IGF-1 by 73 percent and did nothing for memory or decline. In older adults recovering from hip fracture, a trial was stopped early because more people on MK-677 developed heart failure.
The consistent costs are hunger, fluid retention and worse blood sugar: fasting glucose and HbA1c went up and insulin sensitivity went down across studies. FDA lists it as a Category 2 safety risk for compounding, and its advisory committee voted 13 to 1 against allowing it in 2024. The one active drug program, LUM-201 from Lumos Pharma, is a placebo-controlled Phase 3 trial in children with GH deficiency that began in May 2026 and uses a screening test meant to pick out children likely to respond.
Not technically a peptide. MK-677 (Ibutamoren) is listed here because it is discussed and used alongside peptides, but it is not built from amino acids joined by peptide bonds.
What it binds to, and what happens inside the body after that, step by step.
MK-677 is an orally active agonist of the ghrelin receptor (GHS-R1a). It amplifies the body's own GH pulses rather than adding a fixed dose of hormone: pulse height rises, the number of pulses does not, and GH stays under normal feedback control. Because it lasts all day, IGF-1 climbs over the first two to four weeks and stays up with daily dosing. The same receptor drives hunger and modestly raises cortisol and prolactin.
Human results and animal results are kept apart below. A result in rats tells you a mechanism is plausible. It does not tell you what happens in a person.
There are several placebo-controlled randomized trials, so the evidence base is real. They consistently show that 25 mg a day raises GH and IGF-1 to young-adult levels and adds about 1 kg of lean mass, mostly as water and cell mass, without improving strength, function, bone density at most sites, or Alzheimer's progression. The same trials show rising blood glucose, falling insulin sensitivity, fluid retention, and a heart failure signal in frail older adults. Pediatric GH-deficiency results are from company-reported Phase 2 data, with Phase 3 under way.
65 healthy adults aged 60 to 81, 2-year double-blind modified crossover
Lean mass rose 1.1 kg vs a 0.5 kg loss on placebo at 12 months, with no change in strength or function; fasting glucose rose 5 mg/dL and insulin sensitivity fell.
Read the study563 patients with mild to moderate Alzheimer's disease, 12 months
IGF-1 rose 72.9 percent at 12 months but there was no difference from placebo on any cognitive or functional scale.
Read the study123 older adults after hip fracture, 25 mg/day vs placebo
IGF-1 rose by 51.4 ng/mL and gait speed improved slightly, but most function measures did not, and the trial was stopped early for congestive heart failure (4 patients vs 1 on placebo).
Read the study292 women aged 64 to 85 with low femoral neck bone density, 12 to 18 months
Adding MK-677 to alendronate raised femoral neck bone density 4.2 vs 2.5 percent, but not at the spine, total hip or whole body.
Read the study24 obese men aged 18 to 50, 25 mg/day vs placebo for 8 weeks
IGF-1 rose about 40 percent and fat-free mass increased, but total and visceral fat did not change and glucose tolerance worsened.
Read the study8 healthy volunteers on a calorie-restricted diet, crossover
Nitrogen balance was +0.31 g/day on MK-677 vs -1.48 g/day on placebo during a week of dieting.
Read the study8 young adults (crossover) and 6 older adults, 1 to 2 weeks
25 mg at bedtime increased stage 4 sleep by about 50 percent and REM sleep by over 20 percent in young adults; REM rose nearly 50 percent in older adults.
Read the study32 healthy adults aged 64 to 81, 2, 10 or 25 mg/day vs placebo
25 mg/day raised mean 24-hour GH by 97 percent and IGF-1 from 141 to 265 micrograms/L at 4 weeks; fasting glucose rose from 5.4 to 6.8 mmol/L.
Read the studyNo preclinical studies are listed as key studies here. The human data above carries the evidence.
These are questions the published research has not answered.
No product containing MK-677 (Ibutamoren) is approved as a medicine by the FDA.
Not approved anywhere. Merck's programs in frailty, hip fracture, osteoporosis and Alzheimer's disease were stopped. Lumos Pharma licensed it as LUM-201 for pediatric GH deficiency and started a placebo-controlled Phase 3 trial (NCT06948214, about 150 children) in May 2026; a Phase 2 trial of LUM-201 added to oral semaglutide in older adults with obesity is listed as not yet recruiting. WADA names ibutamoren (MK-677) under S2.2.4, prohibited at all times. Products sold online as research chemicals or in supplements are unregulated.
No human half-life has been published for MK-677 (Ibutamoren), so we do not draw a clearance curve. Half-lives quoted online for it are usually estimates from animal data.
This table records the doses that trials and approved labels used, with the source for each row. It is a record of research, not a recommendation, and it is open to free members.
Which symptoms are expected and which mean stop and get help: side effects and red flags.
Tap a claim to see what the studies found.
It is neither. It is a non-peptide ghrelin-receptor agonist that raises your own GH. It does not bind the androgen receptor.
It added about 1.1 kg of lean mass in a year in older adults, partly water and cell mass, but strength and physical function did not improve. No trial has tested it with resistance training in young adults.
In obese men and healthy older adults, total and visceral fat did not fall; body weight and limb fat went up.
One small 1 to 2 week study found about 50 percent more stage 4 sleep in young adults and more REM in older adults. It has not been repeated in a larger or longer trial.
Randomized trials still showed higher glucose, insulin resistance, fluid retention and a heart failure signal in frail older adults.
In 563 Alzheimer's patients, a year of MK-677 raised IGF-1 by 73 percent with no effect on cognitive decline.
These pairings come up often. Almost none have been tested together in a trial, and the evidence note on each says so plainly.
The idea is to protect lean mass during GLP-1 weight loss by raising GH and IGF-1.
EvidenceA Phase 2 trial of LUM-201 plus oral semaglutide in older adults with obesity is registered (NCT07754045) but not yet recruiting, so there are no results. MK-677's glucose effects work against a drug used partly for blood sugar control.
Ghrelin-receptor and GHRH signaling are synergistic, so pairing them is assumed to give larger GH pulses.
EvidenceNo human study has tested MK-677 with any GHRH analog. The added IGF-1 exposure has no safety data.
Not applicable. MK-677 is an oral solid; trial material was given as tablets or capsules. Unregulated powders and liquids sold online have no published stability data.
Not applicable (oral drug).
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