Dr. Pep

Peptides · Oral non-peptide ghrelin-receptor agonist

MK-677: what the studies show

Every line below comes from a study, label or regulator record, checked by two models, with the source linked. Information, not medical advice. For adults 18+.

What it is

  • MK-677 (ibutamoren, MK-0677) is a small-molecule drug taken by mouth that switches on the ghrelin receptor, the body's "hunger hormone" receptor, and so raises growth hormone (GH) and IGF-1. It is not a peptide. Sellers often group it with SARMs.[1][2][3]
  • A related compound, LUM-201, is the same molecule (ibutamoren mesylate) in a company programme for children with GH deficiency.[4][5]

Bottom line

  • MK-677 reliably raises GH and IGF-1 and added about 1 kg of fat-free mass in older adults over a year, but it also raised weight, fasting glucose and cortisol and lowered insulin sensitivity. It failed in Alzheimer disease, and a hip-fracture trial was stopped early over heart failure. It is not an approved drug, and FDA lists it as a compounding substance with significant safety risks.[1][6][7][8]

What the human studies found

  • In a 2-year double-blind RCT in 65 healthy adults aged 60 to 81 (25 mg by mouth daily), GH and IGF-1 rose to young-adult levels. After 1 year, fat-free mass fell 0.5 kg on placebo and rose 1.1 kg on MK-677 (p<0.001). Abdominal visceral fat and total fat mass did not differ. Body weight rose 2.7 kg versus 0.8 kg on placebo. Strength and function outcomes were secondary measures; the abstract highlights the body-composition change.[1]
  • In an RCT in 123 elderly people recovering from hip fracture (25 mg/day for 24 weeks), IGF-1 rose 51 ng/ml but most functional measures did not improve. Gait speed improved (p=0.011), stair-climbing power did not (p=0.292). The trial was stopped early after a signal of congestive heart failure in a small number of patients, and the authors called the safety profile unfavourable in this group.[7]
  • In a 12-month double-blind RCT in 563 people with mild to moderate Alzheimer disease (25 mg daily), IGF-1 rose 60% at 6 weeks and 73% at 12 months, but there was no difference from placebo on any of four disease-progression scales.[6]
  • In an 18-month RCT in 292 postmenopausal women with low bone density, MK-677 25 mg raised bone-turnover markers but, with alendronate, raised bone density only at the femoral neck (4.2% vs 2.5% on alendronate alone), not at the spine, total hip or whole body.[9]
  • In a randomised crossover trial in 22 dialysis patients who finished, MK-0677 for 3 months raised IGF-1 1.76-fold versus 1.07-fold on placebo. Effects on muscle, strength or survival were not tested.[10]
  • Earlier small RCT: in 24 obese men, oral MK-677 25 mg daily for 8 weeks raised IGF-I by about 40% and increased fat-free mass versus placebo.[11]

Known risks and side effects

  • In the 2-year older-adult RCT, fasting glucose rose about 5 mg/dL, insulin sensitivity fell, cortisol rose, and limb fat and body weight rose. The most common side effects were increased appetite (which faded over months), mild leg swelling and muscle pain. LDL cholesterol fell slightly.[1]
  • A congestive heart failure signal ended the hip-fracture trial early. FDA cites this trial as the reason ibutamoren poses significant safety risk.[7][8]
  • In a small trial in GH-deficient adults, fasting and after-meal insulin and after-meal glucose rose with MK-677, and the authors said longer studies were needed to judge this.[12]
  • Case reports in people taking it as a performance supplement include liver enzyme rise after 2 months in a man in his early 30s (resolved after stopping) and reversible gynaecomastia with low testosterone after a supplement mix. Case reports cannot show MK-677 was the cause, and products can contain other drugs.[13][14]
  • Content of products sold as sports enhancers is unreliable. A European study of suspected illegal medicines found ibutamoren was the most-reported molecule, with most samples with quantitative data containing active doses and some overdoses.[15]

Legal status

  • As of the FDA category 2 page (content current 2026-04-22), ibutamoren mesylate is listed as a bulk substance that poses significant safety risks for compounding under both 503A (listed 2023-09-29) and 503B (listed 2022-12-29), because of the potential for congestive heart failure in certain patients.[8]
  • An FDA warning letter dated 2023-06-12 to Warrior Labz SARMS named "MK-677 Ibutamoren" among products sold as SARMs and said products intended to affect the body are drugs under the FD&C Act.[3]

Sources

  1. [1] Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.
  2. [2] Structural basis of human ghrelin receptor signaling by ghrelin and the synthetic agonist ibutamoren.
  3. [3] FDA: Warning Letter, Warrior Labz SARMS (2023-06-12), BPC-157, TB-500, thymosin beta-4, MK-677
  4. [4] The Impact of Ibutamoren on Nonalcoholic Fatty Liver Disease
  5. [5] A GH Secretagogue Receptor Agonist (LUM-201) Elicits Greater GH Responses than Standard GH Secretagogues in Subjects of a Pediatric GH Deficiency Trial.
  6. [6] Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial.
  7. [7] MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study.
  8. [8] FDA: Certain bulk drug substances for use in compounding that may present significant safety risks (503A/503B category 2)
  9. [9] Effect of alendronate and MK-677 (a growth hormone secretagogue), individually and in combination, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women.
  10. [10] Oral ghrelin receptor agonist MK-0677 increases serum insulin-like growth factor 1 in hemodialysis patients: a randomized blinded study.
  11. [11] Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure.
  12. [12] Oral administration of growth hormone (GH) releasing peptide-mimetic MK-677 stimulates the GH/insulin-like growth factor-I axis in selected GH-deficient adults.
  13. [13] Hepatotoxicity induced by MK-677.
  14. [14] Reversible Gynecomastia and Hypogonadism Due to Usage of Commercial Performance-Enhancing Supplement Use.
  15. [15] SARMs, Metabolic Modulators and Growth Hormone Secretagogues in Suspected Illegal Medicines, Bought as Sport Performance Enhancers: A Retro- and Prospective Study Within the GEON.