Somatropin is recombinant human growth hormone (rhGH), identical in sequence to the 191-amino acid pituitary-derived GH. It binds the GH receptor throughout the body to exert a wide range of anabolic and metabolic effects — including stimulation of IGF-1 production in the liver, promotion of protein synthesis and lean mass accrual, lipolysis of adipose tissue, and enhancement of bone mineral density. In research, somatropin is used as the reference standard for studying GH axis biology and as a benchmark for comparing GH secretagogue compounds. Its broad systemic activity reflects the pleiotropic role of endogenous GH in physiology.