Secretion of each of the known anterior pituitary hormones is controlled by one or more hypothalamic releasing or inhibitory factors, interacting with feedback effects of target gland hormones. All of the hormones are peptides, with the exception of dopamine which is a catecholamine and the principal prolactin-inhibiting factor (PIF). Thyrotrophin-releasing hormone (TRH) was the first of the hypophysiotrophic hormones to be chemically characterised (1969) and, between 1969 and 1982, all of the principal hypothalamic regulatory factors had been isolated and their structures elucidated. Furthermore, all have now been synthesised and introduced into clinical medicine.
