Physiology of Growth Hormone in Fetus and Child

Human growth hormone (GH), also known as somatotropin, is a 191-amino acid single-chain polypeptide. Its production begins in early fetal life and is secreted from the anterior pituitary gland in a pulsatile fashion. The GH levels vary during childhood and peak during the pubertal growth spurt. The GH pulse frequency and the amplitude is influenced by a number of factors including age, gender, sleep, nutrition, exercise, and pubertal status. The human growth hormone (GH) gene family is closely related, sharing 90%–99% nucleotide sequence similarity, and is believed to have evolved by gene duplication. The secretion of growth hormone is relatively higher during the early to midadolescence years, about 700 μg/day, approximately double the levels measured in adulthood (~400 μg/day).