Library / Growth hormone

Ibutamoren

Also known as MK-677, MK-0677

Failed trials

Not a peptide: an oral small molecule that mimics ghrelin to raise growth hormone and IGF-1. Phase 2 trials (including hip fracture recovery and Alzheimer disease) did not lead to approval.

Not an approved medicine. Ibutamoren is not an approved medicine for this use in Australia or the United States. This page summarises published research for information only. It is not a recommendation to use Ibutamoren, and VialOwl does not sell or supply it.

Background

Not a peptide: an orally active small molecule (L-163,191, later MK-0677) designed by Merck Research Laboratories and described in 1995 as a non peptide mimic of GHRP-6. Merck ran trials into the 2000s but it was never approved.

How it is thought to work

Taken by mouth, it activates the ghrelin receptor for many hours, raising growth hormone and IGF-1 levels day and night. It also increases appetite and can reduce insulin sensitivity.

What is claimed, and the evidence

Claim	Evidence	Notes
Raising growth hormone and IGF-1 in older adults	Human trials	A 2 year randomised trial in 65 healthy adults aged 60 to 81 raised levels to young adult ranges.
Increasing lean (fat free) mass	Human trials	About 1.1 kg more fat free mass after 12 months versus placebo, but no gain in strength or function.
Faster recovery after hip fracture	Human trials Not supported	Phase 2b trial (123 patients) showed no benefit on most function measures and was stopped early for a heart failure safety signal.
Slowing Alzheimer disease	Human trials Not supported	12 month trial in 563 patients found no effect despite higher IGF-1.
Reversing diet induced protein loss	Small human studies	Short crossover study in 8 healthy volunteers improved nitrogen balance.
Better sleep quality	Small human studies	Small sleep studies in the 1990s.
Muscle building, fat loss and anti ageing as a 'SARM' style supplement	No published evidence	Widely sold online as a research chemical; trials did not show strength or function gains.

Side effects

Effect	How often	Notes
Increased appetite	Common	Most frequent side effect in the 2 year trial; eased after a few months.
Mild swelling of the lower legs (oedema)	Common	Transient in the older adult trial.
Muscle pain	Common	Transient in the older adult trial.
Raised fasting glucose and reduced insulin sensitivity Serious	Common	Fasting glucose rose about 0.3 mmol/L on average.
Weight gain	Common	2.7 kg versus 0.8 kg on placebo over 12 months, partly limb fat.
Raised cortisol	Common	Increased 47 nmol/L on average in the older adult trial.
Congestive heart failure Serious	Uncommon	Safety signal in a limited number of elderly hip fracture patients ended that trial early; cited by FDA.

Warnings

FDA lists ibutamoren as a significant safety risk for compounding because of the potential for congestive heart failure.
Raises blood glucose and reduces insulin sensitivity; long term cancer and mortality effects have not been studied.
It is sold online as a 'research chemical' with no quality control; products may be contaminated or mislabelled.

Regulatory status

Australia: Not included on the ARTG (unapproved). Schedule 4 in the Poisons Standard (listed by name), with Appendix D clause 5 possession controls.
United States: Not FDA approved. In 503A and 503B Category 2 (significant safety risks), citing potential for congestive heart failure.

Sources

Also in Growth hormone

From the VialOwl library, reviewed 26 September 2026. For education and general information. It is not medical advice and not a recommendation to use Ibutamoren.