Non-peptide oral ghrelin receptor agonist and growth hormone secretagogue

Ibutamoren mesylate

aka ibutamoren · MK-677 · MK-0677 · LUM-201 · L-163,191

Evidence grade
Grade B: Moderate human evidence
for raising GH/IGF-1 and lean mass
User score everyone · n = 29
US FDA Not approved FDA safety-risk list (Category 2) · checked 2026-11-13
WADA 2026 Prohibited (S2.2.4) at all times · checked 2026-11-13
EU EU orphan designation for GH deficiency was granted in 2017; FDA's 2024 review found no EMA-authorized product. Orphan designation is not marketing approval. · checked 2026-11-13

Grade note: FDA keeps it in Category 2 for safety; the grade rates efficacy only.

Goals: Sleep · Muscle & strength Compare with another peptide →

User reports

approximate — combined from two independent Reddit reads

Men 45–60

1 man aged 45–60

small sample · n = 1

Outcome mixed 1 of 1

Benefits sleep 1 of 1

Side effects anxiety 1 of 1 · blood pressure 1 of 1 · insomnia 1 of 1 · more hunger 1 of 1 · other 1 of 1 · vivid dreams 1 of 1 · water retention 1 of 1

Stopped 0 of 1 Used with other compounds 1 of 1

All men

3 men

small sample · n = 3

Outcome mixed 1 of 3 · negative 1 of 3 · positive 1 of 3

Benefits muscle 2 of 3 · strength 2 of 3 · joints / tendons 1 of 3 · sleep 1 of 3

Side effects other 2 of 3 · water retention 2 of 3 · anxiety 1 of 3 · blood pressure 1 of 3 · gi upset 1 of 3 · insomnia 1 of 3 · low mood 1 of 3 · more hunger 1 of 3 · tingling / numbness 1 of 3 · vivid dreams 1 of 3

Stopped 0 of 3 Used with other compounds 1 of 3

Everyone

29 people

  • Positive: 18 of 29 (62%)
  • Mixed: 6 of 29 (21%)
  • Negative: 3 of 29 (10%)
  • No effect: 2 of 29 (7%)
  • Unclear: 1 of 29 (3%)
Benefits reported of 29
Benefits reported (n = 29)
ItemReports
Strength14 of 29 (48%)
Muscle12 of 29 (41%)
Sleep10 of 29 (34%)
Recovery4 of 29 (14%)
Fat loss3 of 29 (10%)
Joints / tendons3 of 29 (10%)
Endurance1 of 29 (3%)
Energy1 of 29 (3%)
Side effects reported of 29
Side effects reported (n = 29)
ItemReports
Water retention11 of 29 (38%)
More hunger10 of 29 (34%)
Other6 of 29 (21%)
Insomnia4 of 29 (14%)
Vivid dreams4 of 29 (14%)
Anxiety3 of 29 (10%)
Blood pressure3 of 29 (10%)
Fatigue3 of 29 (10%)
Why people stopped of 29
Why people stopped (n = 29)
ItemReports
Side effects1 of 29 (3%)

Stopped 1 of 29 (3%) Used with other compounds 2 of 29 (7%)

User reports are anecdata, not evidence: self-selected, unverified, often combined with other compounds.

In their words

  • “The hunger was almost immediate.”

  • “My sleep was much better and dreams much more vivid.”

  • “I've noticed around a 30% boost in lean muscle mass”

  • “It made me bloated, upset stomach, greasy face and depressed.”

  • “Since beginning MK 677, I have hit six lifetime PRs on bench press, close grip bench press, shoulder press, squat, and deficit deadlifts.”

  • “The weirdest effects I've noticed is my hands getting numb when holding my phone for a long time while lying down”

  • “I loved everything about it, except it gave me high blood pressure after only 4 days.”

  • “Used mk677 from a very reputable source at 25mg for 6 months, and noticed 0 difference.”

Read summaries and method notes

Read 1. One man aged 45–60: a 46M on MK-677 alongside testosterone reported marked hunger, anxiety, bedtime insomnia, vivid dreams, a mild blood-pressure rise and some water retention; sleep improved after moving the dose to the morning. Across five users, positives were sleep, strength and body composition; negatives were hunger, vivid dreams, GI symptoms, water retention and lethargy. One lower-dose user quit twice because of lethargy and eye-pressure/tunnel-vision symptoms.

Read 2. No man aged 45–60 in allowed subreddits (most MK-677 users are much younger or give no age). Two clearly male users reported big strength and muscle gains, joint healing and better sleep with morning dosing, but also numb hands, irritability, raised blood pressure, hunger and transient erection/libido problems. Everyone (n=25, 7 threads): 16 positive, 4 mixed — strength (12), muscle (11), deeper sleep (8) at 10–30 mg/day for about 8 weeks — against water retention/puffy face (9) and extreme hunger (8), tingling/numbness (3), early insomnia (3) and raised blood pressure (2).

Note 1. Conservative extraction of clear firsthand courses only. The 46M report was stacked with testosterone/HRT, so muscle or strength changes were not attributed to MK-677 unless the user did so.

Note 2. An identical double post was deduplicated. No 45-60 ages in allowed subreddits; r/BodyHackGuide excluded. Almost all reports came from younger or ageless fitness/SARM users; 9 seed threads were unavailable.

Each read counted people independently. Overlap between the two reads is estimated from shared threads and removed; counts are approximate. How we count.

Summary

Not a peptide. Non-peptide spiropiperidine small molecule (MW 624.77 Da) classified as a peptidomimetic. Oral ghrelin mimetic GH secretagogue.

Proposed mechanism

Binds GHS-R1a (ghrelin receptor) in hypothalamus and pituitary → increases GH pulse amplitude and frequency while preserving physiological pulsatility. Blanket absence of endocrine-axis suppression across populations is unestablished. Crosses blood-brain barrier — enables central sleep effects.

Reverse-engineered from peptide GHRP-6 but is a small molecule with oral bioavailability above 60% reported in dogs and an approximately 24-hour biological effect; these are not a verified human bioavailability estimate or plasma half-life — fundamentally different pharmacokinetics from injectable peptide secretagogues like Ipamorelin.

Safety

  • Appetite increase, edema and muscle pain occurred in trials
  • Fasting glucose and insulin resistance can increase
  • Congestive heart failure was a safety signal in frail older adults after hip fracture
  • FDA also identified liver enzyme elevations and hyperprolactinemia
  • No FDA-approved label establishes formal contraindications

From labels, regulators and trials. No signal in small studies ≠ safe.

Evidence B raising GH/IGF-1 and lean mass

B stands, narrowly. One solid 12-month RCT (65 analysed) showed more fat-free mass than placebo, which is the marketed effect. But strength and function did not improve, the hip-fracture trial stopped early for a heart-failure signal, the Alzheimer trial failed, and FDA keeps it in Category 2. The rubric has no safety cap, so B is the rubric answer; a human should decide whether to cap it (see decisions list).

Human trials · 6

  1. PMID 189814852008Randomized double-blind placebo-controlled trial with second-year crossover 71 people

    Healthy adults aged 60–81 years; 65 were evaluated in the first year

    Fat-free mass increased versus placebo, without demonstrated improvement in strength or function; glucose rose and insulin sensitivity fell. Source

  2. PMID 210678292011Randomized double-blind placebo-controlled phase 2b trial 123 people

    Older adults recovering from hip fracture

    IGF-1 rose, functional results were mixed and the study stopped early for a heart-failure signal. Source

  3. PMID 190154852008Randomized double-blind placebo-controlled trial 563 people

    Adults with mild to moderate Alzheimer disease

    No slowing of clinical progression was demonstrated. Source

  4. PMID 93496621997Small placebo-controlled crossover in young adults and uncontrolled comparison in older adults 14 people

    Eight healthy young and six older adults

    Sleep architecture changed in the short study; the older group did not have a placebo period. Source

  5. NCT046143372026Phase 2 randomized open-label active-comparator trial; results posted in 2026 82 people

    Selected prepubertal children with GH deficiency; 104 received a screening dose and 82 entered randomized arms

    At six months, the 1.6 mg/kg arm averaged 8.2 cm/year annualized growth versus 10.6 cm/year with the growth-hormone comparator. Source

  6. NCT069482142026Ongoing phase 3 randomized double-blind placebo-controlled trial; planned enrollment 150 people

    Previously untreated prepubertal children with GH deficiency

    Recruiting in 2026; efficacy and safety results are not yet available. Source

Bar length = trial size on a log scale.

Dose ranges

Reported ranges from labels and studies, with context. Not a recommendation.

  • clinical trial
    25 mg orally once daily in older-adult body-composition and hip-fracture trials Source
  • clinical trial
    0.4–0.8 mg/kg orally daily for six months in a pediatric GH-deficiency study Source

Editorial ratings EDITORIAL

Editors’ judgement, 0–5. Opinion, not data; separate from grade and user score.

Not rated yet.

Sources

  1. pubmed.ncbi.nlm.nih.gov/18981485/
  2. pubmed.ncbi.nlm.nih.gov/21067829/
  3. pubmed.ncbi.nlm.nih.gov/19015485/
  4. pubmed.ncbi.nlm.nih.gov/9349662/
  5. clinicaltrials.gov/study/NCT04614337
  6. clinicaltrials.gov/study/NCT06948214
  7. fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-pres
  8. wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
  9. fda.gov/media/182087/download
  10. fda.gov/media/182088/download
  11. fda.gov/media/185412/download
  12. fda.gov/advisory-committees/advisory-committee-calendar/july-23-24-2026-meeting-pharmacy-c

Reddit threads read · 10

4 further sources on commercial or non-primary hosts not listed.

Research checked 2026-11-13.