Growth hormone (GH) is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland. It stimulates growth, cell reproduction and regeneration in humans and other animals. It is a stress hormone that raises the concentration of glucose and free fatty acids. Secretion of GH in the pituitary is regulated by the hypothalamus. These cells release the peptides GHRH and GHIH into the hypophyseal portal venous blood surrounding the pituitary.. A number of factors are known to affect GH secretion, such as age, sex, diet, exercise, stress, and other hormones.