Ibutamoren (MK-677), CAS no 159634-47-6 has been of interest for biological research in association with aims of increasing muscle mass, improving healing of injures and increasing quality of sleep. While not sufficiently investigated for medical, the body of knowledge regarding ibutamoren consists about one hundred publications.
Growth hormone and hunger
Ibutamoren is a synthetic analogue of ’hunger hormone’ ghrelin. Ibutamoren’s mechanism of action comprises augmentation of natural release of growth hormone according to its natural biorhytm. It is different from synthetic growth hormone that does not follow the natural growth hormone release biorhytm.
According to preliminary research, ibutamoren increases muscle mass but also fat mass in lower extremities, bone mineral density, lowers „bad“ LDL cholesterol, improves sleep and increases appetite. Ibutamoren has been shown to to increase blood sugar levels and lower insuline sensitivity, making it at odds with diabetic condition.
Ibutamoren (MK-677) in elderly studies
While ibutamoren, in a study of the elderly with hip fracture , increased gait speed and reduced number of falls. It also caused elevated blood pressure, increased likelihood of congestive heart failure and increased levels of diabetes markers, suggesting that ibutamoren is not suitable for improving function of the elderly.
In a study of healthy older study subjects it was found that ibutamoren reversed the natural muscle loss and caused the growth hormone profile. It was to be more similar to that of young adults without significant adverse effects . Interestingly, the amount of total body mass increased, total fat mass did not change, yet body fat redistributed somewhat into lower extremities with ibutamoren in comparison with placebo. While ibutamoren has a favourable effect on high density lipoprotein / low density lipoprotein (’good’ / ’bad’ cholesterol ratio) and bone mineral density, it had effects that can aggravate diabetes or increase the risk thereof, as it increased the level of blood sugar.
Ibutamoren (MK-677) in other studies
In addition, ibutamoren increased the level of cortisol . In the overweight men, ibutamoren did not help to decrease weight. It increased the muscle mass but left the fat mass unchanged . Hence, ibutamoren is probably not of interest for research aimed at the cause of weight loss. To the contrary, in a study aimed at reducing body mass loss of young men, ibutamoren was effective of preventing body mass loss .
Ibutamoren’s effect has been researched in association with sleep. The study was very small. The effects of the preliminary study suggested increased sleep quality in association with ibutamoren 
Since ibutamoren increases the release of important growth factor, the scientists have investigated the relevance of the chemical with cancer. Ibutamoren has been researched in association with different types of cancer cells. In one study, the inhibition of cancer cells was found. In the second one, there was no effect. And in the third study, ibutamoren stimulated hormone-producing cancer cells similarly to growth hormone [6,7,8].
It is known that athletes have been using ibutamoren, and it is also known that ibutamoren use in athletes has been associated with competition bans.