MK-677 (Ibutamoren)
Also known as: MK-677, Ibutamoren, MK677, MK 677, Nutrobal, Ibutamoren Mesylate
Orally active GH secretagogue, sold as a SARM but hormonally unrelated — raises growth hormone reliably, and insulin sensitivity is what limits it.
Substance family
Growth hormone itself and the peptides that prompt the body to release it. Effects build over months rather than weeks, and reduced insulin sensitivity is what limits duration.
Effects on
Which outcomes this substance acts on — descriptive, not a recommendation.
Strain profile
Where this substance is most likely to hit — a rough orientation, individually dependent on dose, duration and predisposition.
This substance causes
Dosing & protocols by goal
Rough orientation ranges as reported in harm-reduction literature — not an individual treatment plan. Doses are individual and open-ended; frequency depends on the ester or half-life.
Clinical trials (dose range studied)
MedicalDose
10–25 mg / day
Frequency
1× daily
Cycle length
Up to 2 years in trials on older adults
Investigated for age-related muscle loss and in hip fracture recovery. Trials found raised IGF-1IGF-1The growth factor through which growth hormone does most of its work — and the marker used to gauge HGH dosing. alongside raised blood glucose and reduced insulin sensitivityinsulin sensitivityHow strongly the body responds to its own insulin — worsened by growth hormone and by some blood-pressure drugs..
Muscle gain and recovery (grey market practice)
IntermediateDose
10–25 mg / day
Frequency
1× daily, evening
Cycle length
8–16 weeks, then a break
Unusually, the practical range matches the trial range. Evening dosing aligns with the natural GH pulse in deep sleep.
Lower dose
BasicDose
10 mg / day
Frequency
1× daily, evening
Cycle length
8–16 weeks
Often sufficient for the sleep and recovery effects, with less water retention and a smaller impact on glucose.
Side effect & countermeasure
Typical problems and what you can do to reduce harm — at a glance. Does not replace medical monitoring.
Problem
Rising blood glucose and reduced insulin sensitivity
Countermeasure
The limiting factor, and it appeared consistently in the trials. Growth hormone opposes insulin, and MK-677 raises GH continuously rather than in pulses. Check fasting glucose, HbA1c and fasting insulin before, during and after; metformin or berberine are used to counteract it. Pre-existing insulin resistanceinsulin resistanceHow strongly the body responds to its own insulin — worsened by growth hormone and by some blood-pressure drugs. is a reason not to use it.
Problem
Marked increase in appetite
Countermeasure
MK-677 acts on the ghrelin receptor — the hunger signal. The effect is strong and useful in a mass phase, actively counterproductive in a diet. This is not a side effect that fades; plan meals rather than eating by feel.
Problem
Water retention, puffiness, carpal tunnel symptoms
Countermeasure
The classic sign of too much GH activity. Reduce the dose; symptoms usually resolve within days. Most pronounced in the first weeks.
Problem
Sold as a SARM
Countermeasure
It has nothing to do with androgen receptorsandrogen receptorsThe docking site in the cell that androgens bind to in order to have any effect. and causes no testosterone suppressionsuppressionThe body shutting down its own testosterone production because an external source is present. — that part is genuinely true. But it is not harmless for a different reason: the effect on glucose metabolism is real and dose-dependent.
Problem
Lethargy and heavy sleep
Countermeasure
Common, particularly at higher doses. Evening dosing turns this into an advantage rather than a problem — taken in the morning it interferes with the day.
Problem
Elevated prolactin, occasionally
Countermeasure
Reported at higher doses. If nipple sensitivity or libido changes appear, measure prolactinprolactinA pituitary hormone that, when elevated, causes low libido, erectile problems and breast tissue growth. rather than assuming an estrogen cause.
Overview
MK-677 is sold alongside SARMs and is not one. It does not touch the androgen receptor, causes no suppression of testosterone, and needs no recovery plan. Those claims are accurate.
What it does instead is raise growth hormone and IGF-1 — orally, once daily, without injections. That is genuinely unusual and it is why the substance is interesting. It also reached phase 2 trials, including two-year studies in older adults, which makes it better documented than most things sold in this corner of the market.
Those same trials identified the problem.
Mechanism of Action
Ghrelin is the hormone that signals hunger, and it also triggers growth hormone release. MK-677 mimics ghrelin at its receptor — non-peptide, so it survives digestion and works as a tablet, which peptides like ipamorelin cannot.
The GH increase is reliable and IGF-1 rises measurably. Unlike injected HGH, release stays under the body's own regulation, so the extremes of exogenous growth hormone do not occur.
But the elevation is continuous rather than pulsatile, and that is where the trade-off sits. Growth hormone opposes insulin, and a sustained elevation reduces insulin sensitivity. The two-year trials in older adults found exactly that: raised IGF-1 alongside raised fasting glucose and reduced insulin sensitivity. One trial in Alzheimer's patients was stopped partly over cardiovascular concerns, including heart failure signals.
The ghrelin mechanism also brings the effect nobody warns about adequately: appetite. Not mild appetite improvement — a strong, persistent hunger signal that does not fade with continued use. In a mass phase that is useful. In a diet it works directly against the goal, which is why MK-677 is one of the few compounds that is genuinely the wrong tool for cutting.
Typical Context
Ten to twenty-five milligrams daily, taken in the evening, over eight to sixteen weeks with breaks. Evening dosing is not arbitrary — the natural GH pulse occurs in deep sleep, and the sedating effect becomes an advantage rather than a nuisance.
The lower end of the range is often enough for the sleep and recovery effects. Water retention and glucose impact both scale with the dose, and the additional benefit above ten milligrams is smaller than the additional cost.
Anyone with existing insulin resistance, prediabetes or a family history of type 2 diabetes should treat this as a reason not to use it rather than something to monitor around.
Side Effects & Risks
- Rising blood glucose and reduced insulin sensitivity — the limiting factor
- Marked, persistent increase in appetite
- Water retention, puffiness, carpal tunnel symptoms
- Lethargy, heavy sleep
- Elevated prolactin occasionally at higher doses
- Cardiovascular concerns raised in one trial population
- No hormonal suppression, so no recovery plan needed
Blood Work & Monitoring
- Fasting glucose, HbA1c and fasting insulin — the values that decide whether it can continue
- IGF-1 — the practical measure of effect
- Prolactin — if nipple or libido symptoms appear
- Blood pressure — measured at home
Harm-Reduction Notes
- Insulin sensitivity is the limit — measure glucose and HbA1c, not just IGF-1
- Not a diet compound; the appetite effect works directly against a deficit
- Evening dosing turns the sedation into an advantage and matches the natural GH pulse
- Water retention and carpal tunnel symptoms mean the dose is too high
- Pre-existing insulin resistance is a reason to skip it entirely
- It is not a SARM and needs no PCT — but that says nothing about the metabolic risk
- Only sources with an independent analysis
Legal status by region
Regulation differs considerably between jurisdictions and changes over time. This is a rough orientation, not legal advice — check the rules that apply where you are.
| Region | Regulatory status |
|---|---|
| United States | Not approved for human useSold as a research chemical; the FDA has warned about products marketed as SARMs. |
| EU / UK | No marketing authorisation |
| Most other jurisdictions | Unregulated grey area |
| Competitive sport | Prohibited at all timesListed by WADA under S2 as a growth hormone secretagogue. |