Somatotropin

Abstract

Somatotropin is a protein hormone secreted from the anterior pituitary gland under the action of growth hormone-releasing factor (stimulatory) and somatostatin (inhibitory) released from the hypothalamus. Somatotropin can vary slightly in size, generally about 191 amino acids, and the amino acid sequence also varies among species. Whereas bST and pST share a high degree of sequence similarity (ca. 90%), both have a much lower homology with human ST (ca. 65%) and hence are inactive in humans. Since ST is a protein, it is digested if consumed orally, and exogenous ST has to be administered via injection or implant.