Ibutamoren

Ibutamoren (also known as MK-677, L-163,191, and Nutrobal) is a non-peptide, long-acting, orally-active, and selective agonist of the ghrelin receptor and a growth hormone secretagogue, mimicking the growth hormone (GH)-stimulating action of the endogenous hormone ghrelin. It has been demonstrated to increase the release of, and produces sustained increases in plasma levels of several hormones including GH and insulin-like growth factor 1 (IGF-1), but without affecting cortisol levels.

Pharmacology

Ibutamoren is frequently discussed on online forums for its reputed anabolic muscle-building properties. It is available over the counter and used by those wishing to increase their growth hormone levels. However, clinical studies have shown that it does not significantly alter GH levels; instead, it increases IGF-1 levels. Ibutamoren has been shown to sustain activation of the GH–IGF-1 axis and to increase lean body mass with no change in total fat mass or visceral fat. It is orally active, and can be taken once a day.

Clinical trials

Several studies have been done on Ibutamoren, and it has been shown to increase IGF-1 levels in both men and women. In one study, the subjects showed an increase in lean body mass but no increase in strength. It is unclear if this increase in lean body mass was due to an increase in muscle, bone, or water retention.

Side effects

The side effects of Ibutamoren are generally mild and tend to diminish over time. Some of the common side effects include increased appetite, mild lower extremity edema, and muscle and joint pain. Several studies have also suggested that Ibutamoren may alter the action of certain hormones, which could lead to potential health risks. For example, it may increase prolactin levels, which may affect menstrual cycle in women and cause sexual dysfunction in men.

Legal status

Ibutamoren is currently not approved by any health regulatory authority for medical use. However, it is available over the counter for research purposes.

See also

• Ghrelin receptor
• Growth hormone secretagogue
• Insulin-like growth factor 1