Somatotropin, also commonly referred to as human growth hormone (HGH), is a hormone that is produced in the human body and excreted into the blood by the somatotrope cells of the anterior pituitary gland. It is a single-chain protein that is composed of 191 amino acids with a molecular weight of approximately 22,000 Daltons.

GH secretion has many direct and indirect effects on the human body. First, GH stimulates the liver's production of insulin-like growth factor (IGH-1). Because GH stimulates the liver's production of IGF-1, the effects of both GH and IGF-1 are listed below.

Synthetic version of Human Growth Hormone is called Somatropin (191 amino acid sequence growth hormone). It is identical to human body's own GH. However that is not the case for Somatrem (192 amino acid sequence growth hormone).