MK-677 (Ibutamoren)
MK-677 (Ibutamoren) — evidence, the oral-GH story & status

Class: small_molecule
Synonyms: MK-677
MK-0677
Ibutamoren (mesylate)
Merck code L-163,191
pediatric development name LUM-201. INCI: none. Not a peptide and not a SARM (see below)
Function tags: GH secretagogue (oral)
body composition
slow-wave sleep
appetite (research / gray-market)
Overall evidence grade: B
WADA prohibited: yes
WADA note: Sport: WADA-prohibited at all times — Section S2 (GH secretagogues / ghrelin mimetics); directly detectable.
Last updated: 2026-07-10

In brief: MK-677 (ibutamoren) is an oral, non-peptide ghrelin-receptor agonist — the pill version of the injectable GHRPs. Across ~30 years of trials it reliably raises GH and IGF-1 and deepens slow-wave sleep, and it modestly increases lean mass — but without improving strength or physical function, and at a real metabolic cost (insulin resistance / elevated blood glucose). It's not FDA-approved (the FDA is recalling consumer products that contain it), it carries a congestive-heart-failure safety signal from an elderly trial, and it's banned in sport. It is not a peptide and not a SARM.

## Identity a **non-peptide small molecule** — a **spiroindanylpiperidine (~529 Da)**, chemically closer to a conventional drug than to a peptide. Synthesised in 1995 by Arthur Patchett's team at **Merck** (Patchett, PNAS 1995; Smith, Science 1997) as an **orally active** growth-hormone secretagogue. It is a long-acting (elimination **half-life ~24 hours**, supporting once-daily use) agonist of the **ghrelin receptor (GHS-R1a)** — the **same receptor** as the injectable GHRPs (GHRP-6 #24, GHRP-2 #23, Ipamorelin #17, Hexarelin #21), but taken by mouth. ## Mechanism (as proposed) binds **GHS-R1a** (the ghrelin receptor) on hypothalamic and pituitary somatotrophs → **pulsatile GH release** (mimicking the body's natural overnight pattern) → hepatic **IGF-1**, which drives the downstream muscle/fat/bone/sleep effects. It also mimics ghrelin's **appetite** signal (relentless hunger). Its oral, small-molecule nature and long half-life are what distinguish it from the injectable GHRPs — as is its tendency to **raise blood glucose** with sustained use.

Evidence grades by outcome:
outcome: GH / IGF-1 elevation
grade: B
base: ~30 years of trials (Chapman 1996; Svensson 1998; many)
effect: Sustained rise in GH & IGF-1
caveat: Well-established biomarker effect — which is not the same as a clinical benefit
outcome: Slow-wave (deep) sleep
grade: B
base: Documented across trials
effect: Meaningful increase in stage-IV sleep
caveat: A genuine, often most-noticed effect
outcome: Fat-free (lean) mass
grade: C
base: Nass 2008 (Ann Intern Med, 2 yr, n=65): FFM +1.1 kg
effect: Modest lean-mass gain
caveat: No strength or functional improvement — the key honest limit
outcome: Anti-aging / physique / strength (the popular use)
grade: F
base: Lean-mass gain doesn't translate to function; appetite drives fat gain
effect: Not demonstrated for these goals
caveat: The FFM gain ≠ performance; ghrelin-driven hunger causes fat gain in physique use
outcome: Failed / halted indications
base: Alzheimer's (Sevigny 2008 — no effect); hip-fracture trial (Adunsky 2011) terminated early on a CHF signal
effect: Negative / safety-halted
caveat: The congestive-heart-failure signal in elderly is a serious flag
outcome: Safety
base: Multiple trials
effect: Real concerns
caveat: Insulin resistance / elevated fasting glucose (primary risk); lower-extremity edema; appetite → fat gain; modest prolactin rise; theoretical oncogenic concern (sustained IGF-1); CHF signal; WADA-banned

Legal status:
region: US
status: Not approved
note: Not FDA-approved for any indication (30 years on, still unapproved; Merck shelved it, and Lumos's LUM-201 is in pediatric development, not approved). The FDA is actively enforcing against unapproved consumer products — a consumer alert on "iKids-Growth" (Sept 2025) and a recall of "Agebox" products containing undeclared ibutamoren (March 2026). It is not a scheduled substance, but selling it in supplements is unlawful.
region: EU
status: Not approved
note: not approved.

Cosmetic claims:

Note: Reference entry — not sold here. The oral, non-peptide sibling of the injectable GHRPs: same ghrelin-receptor mechanism, but a pill. Included because the demand is enormous and it sits right next to the GH-peptide cluster — honestly tagged as not a peptide. No dosing published here.

Sources:
Patchett AA, et al. (A nonpeptidyl growth hormone secretagogue.) PNAS. 1995; Smith RG, et al. Science. 1997.
Chapman IM, et al. (Stimulation of the GH/IGF-1 axis by oral MK-677.) J Clin Endocrinol Metab. 1996.
Nass R, et al. Effects of an oral ghrelin mimetic on body composition in healthy older adults. Ann Intern Med. 2008. (FFM +1.1 kg, no strength gain.)
Sevigny JJ, et al. (MK-677 — no clinical effect on Alzheimer's progression.) Neurology. 2008; Adunsky A, et al. (Hip-fracture trial terminated on CHF signal.) 2011.
Lumos Pharma — LUM-201 (OraGrowtH210/212) pediatric GHD Phase 2.