Molecular evolution of growth hormone

Growth hormone (GH) is a single-chain protein hormone of about 190 residues, expressed mainly in the vertebrate anterior pituitary gland, which regulates somatic growth and various aspects of metabolism; many of these actions are mediated by insulin-like growth factor 1 (IGF1). Growth defects in humans frequently result from GH deficiency and are often treatable by GH administration. The evolution of GH illustrates many features of molecular evolution, including (i) the development and elaboration of gene/protein families by gene duplication, (ii) subtle changes resulting from incorporation of point mutations, which often occur during episodes of accelerated change, and (iii) co-evolution of hormones and their receptors.