MK-677 (Ibutamoren)

What it is

MK-677 — also called Ibutamoren — is the only ghrelin-receptor agonist in this whole class that you can swallow. Everything else in the GH-secretagogue world is an injection: GHRH side (Sermorelin, CJC-1295, Tesamorelin) or ghrelin side (Ipamorelin, GHRP-2/6, Hexarelin). MK-677 is a small molecule, not a peptide — it survives your stomach acid and first-pass liver metabolism, which is why it works orally. It binds the GHS-R1a ghrelin receptor in the pituitary and hypothalamus, your pituitary releases a real GH pulse, and IGF-1 stays elevated for hours.

That oral property is the whole reason this compound exists. Merck developed it in the 1990s as an HGH substitute for muscle wasting, osteoporosis, and age-related GH decline. The regulatory context matters: the 1990 Crime Control Act amended the Federal Food, Drug, and Cosmetic Act to add criminal penalties for distributing HGH for anything other than recognized disease, which effectively closed off-label HGH for wellness and longevity. That created a commercial gap. MK-677 was Merck’s answer — an oral, patentable, HGH-equivalent that bypassed the wall.

The program ended in a hip-fracture trial that we’ll cover below. Merck shelved it; the molecule’s structure became public; the research-chemical market filled the void; and in 2023 the FDA added MK-677 to the 503A “do not compound” list. That means licensed US compounding pharmacies can’t legally produce it for human use. The rights ended up with Lumos Pharma, which is developing it as LUM-201 for rare pediatric growth disorders.

How it works

MK-677 is a selective agonist at GHS-R1a, the ghrelin receptor. When ghrelin (your “hunger hormone,” made in the stomach) hits that receptor on pituitary somatotrophs, it triggers a pulsatile GH release. MK-677 mimics that signal — pharmacologically and behaviorally — with sustained oral presence.

The downstream cascade: GH pulse → liver IGF-1 production → systemic IGF-1 elevation. That elevation is what drives the muscle/bone/skin/sleep effects users chase. Magnitudes are commonly cited at roughly 2–3 IU/day of exogenous HGH equivalent at standard doses, though that comparison is rough — pulsatile endogenous GH and continuous exogenous HGH behave very differently downstream.

Here’s the structural map worth holding, because it’s the entire reason MK-677 cross-sells to injectable secretagogues:

Class	Receptor	Examples
GHRH-receptor agonists	GHRH-R on pituitary	Sermorelin, CJC-1295, Tesamorelin (all Alyve SKUs)
Ghrelin-receptor agonists	GHS-R1a	Ipamorelin (Alyve SKU), GHRP-2, GHRP-6, Hexarelin, MK-677 (oral)

MK-677 and Ipamorelin hit the same receptor. The molecules are different — MK-677 is non-peptide, Ipamorelin is a synthetic pentapeptide — and that’s where the side-effect profiles diverge. Ipamorelin was engineered specifically for selective GHS-R1a binding, meaning it triggers GH release without the off-target hunger, cortisol, and prolactin spikes you get from broader ghrelin agonism. MK-677 has no such selectivity — it brings the whole ghrelin-pathway baggage along for the ride. That’s not a knock on MK-677; it’s just the engineering trade-off you sign up for when you trade an injection for a pill.

What the research shows

MK-677 has a real human evidence base — more than most peptides in this wiki — and the picture it paints is mixed in a useful, informative way.

Adunsky et al. — the elderly hip-fracture RCT. This is the most important MK-677 study to know. Elderly post-surgical hip-fracture patients, 25 mg/day oral, roughly 123 randomized (62 ibutamoren / 61 placebo). The cardiovascular signal: congestive heart failure in 4/62 (6.5%) on MK-677 vs 1/61 (1.7%) on placebo. The trial was terminated early. The mechanistic explanation is straightforward — GH-driven fluid retention unmasked subclinical cardiac dysfunction in a frail elderly population. This finding is what ended Merck’s program. It does not mean MK-677 causes heart failure in healthy adults; it means in a population with thin cardiac reserve, adding fluid retention on top of recent surgery was enough to push some patients over the edge. Lead with this fact in any honest write-up.

Nass et al. — 2-year healthy-elderly RCT. Healthier older adults, two years of daily oral MK-677. GH and IGF-1 rose and stayed up. Lean body mass went up, body weight went up. Fasting glucose rose ~5 mg/dL (~0.3 mmol/L) and HbA1c crept up — modest in absolute terms but a real insulin-resistance signal in a population already at metabolic risk. Bone mineral density improved (the original Merck osteoporosis target). This is the central long-term trial: the benefits are real, the metabolic cost is real, the trade-off is real.

Sleep architecture. Multiple smaller human studies in both young and older adults document an increase in deep (slow-wave) sleep duration on MK-677. This is the “I sleep like a rock” effect biohackers report. It tracks the natural overnight GH pulse and is one of the most consistently reported subjective benefits.

The mechanism map (broad pharmacology) [ESTABLISHED]. GH-driven water retention, GH-driven reduction in insulin sensitivity, and ghrelin-driven appetite stimulation are all well-established endocrinology. MK-677’s clinical effects are the predictable downstream of doing what it’s designed to do.

Practitioner-level reporting. Dr. Alex Tatem — urologist, men’s health specialist — disclosed a personal 12-week MK-677 cycle at 25 mg/day (legally prescribed in 2022, before the FDA listing). Two things from his disclosure are worth knowing: his A1C went to 5.7 (pre-diabetic range) and came back down after he quit, and he experienced enough water-retention-driven cardiovascular strain that a Boulder Flatirons hike he’d done dozens of times stopped him in the parking lot. That’s a single physician’s experience, not a controlled trial — but it lines up cleanly with the Nass glucose data and the Adunsky CHF mechanism. Honest first-person data from someone who runs labs on himself is worth surfacing.

Where the evidence runs out: long-term safety in healthy adults is not characterized. MK-677 has never been FDA-approved for any indication; the Merck trials were the closest thing to clean efficacy data and they ended before reaching that question.

Real-world protocol

The doses and schedules here are for educational and informational purposes only. MK-677 is sold for research use only and is not an FDA-approved drug. This is not medical advice. Consult a qualified physician before beginning any protocol.

MK-677’s defining property is that there is no reconstitution math. It’s oral. Capsules or a liquid solution from a research vendor; one dose, once a day, swallowed.

Dose range studied: 5–25 mg/day. Most community protocols and the Merck trials clustered at 10–25 mg/day.

Practical dosing tiers:

• Low / longevity-only: 5–10 mg/day — captures the sleep + IGF-1 baseline lift with milder water retention and metabolic impact.
• Standard: 10–15 mg/day — most biohacker community ranges.
• High (bulking): 20–25 mg/day — the Merck trial dose; maximizes muscle/appetite/sleep effect, also maximizes water retention, insulin-resistance, and CV-strain risk.

Timing: Once daily, usually before bed. The reason: it leverages the natural overnight GH pulse, and the deep-sleep effect helps with sleep onset and architecture. Splitting AM/PM is done by some users but pushes the metabolic side effects harder.

Cycle: Community convention is 8–12 weeks on, 4–8 weeks off — and unlike the injectable GHRPs (see GHRP-2, GHRP-6, and Hexarelin — the injectable ghrelin-receptor GH peptides), MK-677 doesn’t show rapid receptor desensitization, so some long-term users run it continuously. Whether that’s wise given the 2-year Nass glucose creep is the open question — cycling gives your insulin sensitivity a reset window, and that’s probably the more defensible default.

Harm-reduction operational rules (the Tatem framing, lifted with his self-experimentation in mind):

• Monitor blood sugar. Baseline fasting glucose + HbA1c before, every ~8 weeks during, post-cycle.
• Watch blood pressure — water retention pushes it up.
• Do cardio — offsets the CV strain from fluid load.
• Keep the dose in the 10–15 mg range unless you have a specific bulking reason to go higher.
• Cycle off. Do not run it indefinitely without monitoring.

Use-case fit:

• Bulking + hard-gainer profile. The ghrelin hunger becomes the therapeutic mechanism. Water retention masked by mass gain. The compound’s strengths align with the goal.
• Cutting / fat-loss. Avoid. The hunger sabotages the diet; water retention hides progress; insulin resistance works against fat-loss physiology.
• Cardiac history (especially anything reduced-ejection-fraction). Avoid. The Adunsky signal is what it is.
• Tested athlete. WADA-banned. Not a question.

The injectable alternative — and why most informed users end up there. Ipamorelin hits the same receptor without the ghrelin off-target effects: no significant hunger, no meaningful cortisol/prolactin elevation, no water retention to the same magnitude, no insulin-resistance signal. The trade-off is one subcutaneous shot a day instead of one pill. For most use cases — sleep, recovery, body comp, IGF-1 baseline — Ipamorelin (often blended with CJC-1295 in the CJC-1295 / Ipamorelin stack) is the cleaner, better-engineered answer to what MK-677 was originally trying to solve.

Side effects & management

The side-effect profile is well-characterized — both from the Merck trials and from broad community use. Stated plainly, not scarily:

Effect	Mechanism	Practical notes
Ravenous appetite	Direct ghrelin-receptor agonism	Asset for bulking; deal-breaker for cutting
Water retention / edema	GH-driven fluid retention	Hands, feet, face; masks definition; raises BP; the CV-strain mechanism behind Adunsky’s CHF signal
Insulin resistance / fasting glucose rise	GH/IGF-1 reduce insulin sensitivity	Nass: ~5 mg/dL fasting glucose, HbA1c creep at 2 years; Tatem: A1C to 5.7 on 12 weeks at 25 mg/day
Lethargy / daytime fatigue	Possibly REM rebound / circadian shift	Most pronounced first 2–4 weeks
Modest prolactin rise	Off-target ghrelin-pathway signaling	Usually upper-end of normal at standard doses
Blood pressure elevation	Fluid retention	Track it
Vivid dreams	Deep-sleep / REM shift	Most users report this as a positive

Management defaults: dose at the low end of the range; cycle off; monitor metabolic labs; do cardio; eat for the goal (don’t fight the hunger if you’re bulking, don’t run this compound if you’re cutting).

Hard-stop populations (where the risk-reward genuinely doesn’t pencil):

• Active or recent CHF, significant reduced ejection fraction, recent major cardiac event.
• Active or pre-existing diabetes — the insulin-resistance signal compounds.
• Active malignancy or active cancer-history concern — IGF-1 is a mitogen.
• Elderly with subclinical cardiac vulnerability (the Adunsky population).

Regulatory status

Never FDA-approved for human use. In 2023, the FDA added MK-677 to the “do not compound” Category 2 list, which means US compounding pharmacies cannot legally produce it for human consumption. Sold worldwide as a “research chemical” — legal gray area, not labeled for human consumption. WADA-banned in sport. Rights with Lumos Pharma (LUM-201 pediatric growth disorder program). The 1990 Crime Control Act background — which closed off-label HGH and motivated MK-677’s original development — is part of the historical context but doesn’t directly apply to MK-677’s current status.

The Alyve product

MK-677 is not in Alyve’s current launch catalog — flagged as a roadmap candidate. The 2023 FDA do-not-compound listing is a real headwind for any verified-vendor wanting to add it, and the CHF + insulin-resistance signals make this a higher-friction addition than the cleaner GH-axis SKUs already in the catalog (Ipamorelin, CJC-1295, CJC-1295 / Ipamorelin, Sermorelin, Tesamorelin).

The honest position for OHM readers researching MK-677: the injectable GHS-R1a agonist that solves the same problem with a far cleaner side-effect profile is available, US-manufactured, COA-verified at >99% purity, and in Alyve’s launch lineup. Ipamorelin was engineered specifically to do what MK-677 does — hit the ghrelin receptor for a GH pulse — without the hunger, water retention, and metabolic baggage. Stacked with CJC-1295 in the CJC-1295 / Ipamorelin blend (in stock, 99.90% Freedom Diagnostics COA, lot CJI583), it’s the dual-receptor GH-axis stack that the broader peptide world moved to once MK-677’s problems became clear.

Offer: Use coupon OHM-15 for 15% off — Alyve’s pricing is very competitive, and buying 3 vials of any given peptide in one purchase gets you over 30% off retail. (Full disclosure: OHM-15 attributes the sale to me — said plainly, as always.)

Sources

1. Adunsky A, et al. Ibutamoren mesylate in elderly hip-fracture patients — RCT, terminated for CHF signal.
2. Nass R, et al. Two-year MK-677 (ibutamoren) in healthy older adults — GH/IGF-1, lean mass, glucose, BMD.
3. Sleep-architecture trials of MK-677 (young + older adults).
4. FDA 503A Category 2 “do not compound” listing, 2023 — MK-677 addition.
5. Lumos Pharma — LUM-201 pediatric growth disorder program (MK-677 / ibutamoren successor development).
6. Tatem A. “MK-677 Review by a Doctor — Is It Safe or Hype?” (urology / men’s health video; 12-week personal cycle disclosure, A1C 5.7, water retention CV strain).
7. Research note — Follistatin-344 + MK-677 cluster (text aggregation, mechanism + Adunsky + Nass + sleep data).
8. Alyve COA summary (none for MK-677 — not in launch catalog).

See also: Ipamorelin, CJC-1295, CJC-1295 / Ipamorelin, Sermorelin, Tesamorelin, GHRP-2, GHRP-6, and Hexarelin — the injectable ghrelin-receptor GH peptides.