A signaling protein in the same family as myostatin, also bound and neutralized by follistatin.

A compound that prompts the body to release its own hormone rather than supplying that hormone directly. A growth hormone secretagogue makes the pituitary release growth hormone; it is not growth hormone.

Binding free actin so it cannot assemble into filaments, which influences how cells move and reorganize. The described mechanism of thymosin beta-4 and of the TB-500 fragment.

A hormone released by the pituitary that drives growth and influences metabolism and body composition. Many compounds in this library act on the systems controlling it rather than being it.

A muscle stem cell that activates in response to damage and contributes to repair. Central to the claims made for MGF.

Growth hormone-releasing hormone. The body’s own signal telling the pituitary to release growth hormone. Sermorelin, CJC-1295 and tesamorelin are all analogues of it.

An enzyme that extends telomeres, the protective caps on chromosomes. The most cited claim about Epitalon rests on telomerase activity observed in cell culture that has not been widely reproduced.

Another name for the first 29 amino acids of GHRH, the portion carrying its activity. Sermorelin is that sequence unmodified; Mod GRF 1-29 is a modified version of it.

A lipid in the inner mitochondrial membrane, essential to how mitochondria function. Abnormalities in it underlie Barth syndrome, the approved indication for SS-31.

Insulin-like growth factor 1. A hormone made mainly by the liver in response to growth hormone. Much of what growth hormone does downstream, it does through IGF-1.