MK-677 Side Effects, Including Hair Loss
MK-677 side effects from three published human trials: fasting glucose, edema, cortisol, testosterone. Plus what is - and is not - established about hair loss.
The short version
MK-677 (ibutamoren) has never been approved by the FDA, and FDA itself flags a congestive-heart-failure signal from a hip-fracture trial that was stopped early. Three other published human trials, in older adults and obese men, report a consistent pattern. It includes increased appetite, fluid retention and muscle pain, a rise in fasting glucose with reduced insulin sensitivity, a small rise in cortisol, and reduced testosterone in men. No published human trial has studied hair loss on MK-677, so that link is not established.
- FDA's own safety flag on ibutamoren is a congestive heart failure signal from a hip-fracture trial stopped early.
- Three other published trials report increased appetite, edema, muscle pain, fasting-glucose rise, cortisol rise and reduced testosterone.
- No published human trial has measured hair loss or hair thinning on MK-677. It is not an established side effect, in either direction.
- Get emergency care for shortness of breath, rapid swelling or chest pain; call Poison Control for a suspected overdose.
US legal status - Research use only
MK-677 (ibutamoren) has never been FDA-approved for any indication. It is not a controlled substance, but FDA lists it as Category 2 for compounding safety risk.
For what MK-677 is and its mechanism, see the main MK-677 page. For the doses the trials below used, see MK-677 dosage. This page covers the side-effect and safety record.
FDA’s own flag: a heart-failure signal
FDA’s list of bulk drug substances that may present significant safety risks in compounding has an entry for ibutamoren mesylate. It cites a randomised, placebo-controlled trial in patients recovering from hip fracture that was terminated early over a potential safety signal of congestive heart failure.
The entry is Category 2 under both 503A and 503B compounding rules, FDA’s designation for substances it has identified as presenting significant safety risks. That trial is not one of the three cited below. It is a separate study FDA references in its own finding. It is why shortness of breath and unexplained swelling appear in the “get care now” list on this page.
What three published human trials report
Small or uncontrolled human studies. Too little to settle the question either way. Three published human trials tested MK-677 at 25 mg/day (one also tested 2 and 10 mg) in older adults and obese men, for 8 weeks to 2 years. None enrolled young, healthy adults training for muscle, and none measured hair as an outcome.
None of these four papers enrolled young, healthy adults training for muscle, the population most vendors market MK-677 to. None measured hair, skin or cosmetic outcomes of any kind.
Hair loss: not established
Hair loss is one of the most common searches about MK-677, so I looked for evidence on it directly.
One trial found a small rise in cortisol on MK-677: an increase of 47 nmol/L from baseline versus placebo Nass 2008 - Nass R, Pezzoli SS, Oliveri MC et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008;149(9):601-11., in the references below. Elevated cortisol is a recognised trigger of telogen effluvium, a temporary, diffuse shedding pattern. That is a general physiological mechanism, not a finding specific to MK-677.
No study has tested whether the cortisol change in that trial is large or sustained enough to cause measurable hair shedding in anyone. Reports of MK-677 hair loss in forums and vendor marketing are not attributed to any study I could verify by fetching it. This page reports the cortisol finding on its own and does not turn it into a hair-loss claim.
Who should not use it
No FDA-reviewed contraindication list exists for MK-677, because it has never completed that review. Based on FDA’s heart-failure signal and the findings above, these people should avoid it:
- Anyone with a personal or family history of heart failure or cardiac risk factors
- Anyone with diabetes or impaired glucose tolerance - fasting glucose rose in every trial that measured it
- Anyone pregnant or breastfeeding
- Children - none of the trials studied paediatric use
The trials’ eligibility rules describe who a monitored study considered eligible. They are not a safety clearance for anyone outside them.
Related
- Does MK-677 cause hair loss?
- MK-677 (Ibutamoren): the non-peptide GH secretagogue
- MK-677 dosage: what the human trials actually used
- Dosage calculator
- Are peptides safe?
Common questions
What are the known side effects of MK-677?
FDA's bulk-drug-substance safety listing flags a congestive heart failure signal from a randomized trial in hip-fracture patients, which was terminated early over that signal. Three other published human trials, in older adults and obese men, report a consistent pattern beyond that. It includes increased appetite, transient lower-leg swelling and muscle pain, a rise in fasting glucose with reduced insulin sensitivity, a small rise in cortisol, and reduced total testosterone in men.
Does MK-677 cause hair loss?
This is not established. I searched the published literature and found no human trial or case report that measured hair loss, thinning or shedding as an outcome of MK-677 (ibutamoren). The three published human trials this page cites did not report hair as an outcome. Hair-shedding reports in forums and marketing material are not attributed to any study I could verify, so this page does not present them as an established effect.
Why might people connect MK-677 to hair loss even without a study?
One published trial measured a small rise in cortisol on MK-677. Elevated cortisol is a recognised trigger of telogen effluvium, a temporary, diffuse hair-shedding pattern, but that is a general physiological association, not a finding about MK-677. No study has tested whether MK-677's cortisol rise causes measurable hair shedding in anyone. Treat the connection as an unstudied hypothesis, not a documented effect.
What is FDA's specific safety concern with MK-677?
FDA's list of bulk drug substances that may present significant safety risks in compounding includes ibutamoren mesylate, citing the potential for congestive heart failure in certain patients. It cites a randomized, placebo-controlled trial in patients recovering from hip fracture that was terminated early over a potential safety signal of congestive heart failure. It is Category 2 under both 503A and 503B, meaning FDA has identified it as presenting significant safety risks for compounding.
What did the fasting-glucose and testosterone findings actually show?
In a dose-ranging trial, fasting glucose rose from 5.4 to 6.8 mmol/L at 4 weeks on the 25 mg dose. A 2-year trial in older adults found fasting glucose rose about 0.3 mmol/L with reduced insulin sensitivity. In an 8-week trial in obese men, oral glucose tolerance was impaired at 2 and 8 weeks, and the same cohort showed reduced total serum testosterone compared with placebo.
When should I stop and get medical care?
Get emergency care (call 911 in the US) for shortness of breath, rapid or unexplained swelling, or chest pain. Do the same for signs of a severe allergic reaction, such as facial or throat swelling and difficulty breathing. These overlap with the heart-failure signal FDA has flagged. For a suspected overdose or a reaction that is not an emergency, call Poison Control at 1-800-222-1222, free and confidential around the clock.
References (6 sources)
Bibliographic detail is fetched from PubMed, not written by me - so a citation here cannot drift from the paper it names. Study design comes from PubMed's own tags rather than my judgement.
- 1.Chapman IM, Bach MA, Van Cauter E et al. Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretogogue (MK-677) in healthy elderly subjects. J Clin Endocrinol Metab. 1996;81(12):4249-57.Randomised trialPMID 8954023
- 2.Nass R, Pezzoli SS, Oliveri MC et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008;149(9):601-11.Randomised trialPMID 18981485full text
- 3.Svensson J, Lönn L, Jansson JO et al. Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure. J Clin Endocrinol Metab. 1998;83(2):362-9.Randomised trialPMID 9467542
- 4.Svensson J, Carlsson B, Carlsson LM et al. Discrepancy between serum leptin values and total body fat in response to the oral growth hormone secretagogue MK-677. Clin Endocrinol (Oxf). 1999;50(4):451-6.Randomised trialPMID 10468903
- 5.FDA - Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Ibutamoren mesylate entry: category 2 under 503A and 503B, congestive heart failure risk, hip-fracture RCT terminated early.- US Food and Drug Administrationregulatory
- 6.America's Poison Centers - confirms 1-800-222-1222 as the national Poison Control number, free, expert and confidential.- America's Poison Centersother