Hypothalamus: Releasing and Inhibiting Hormones

A. Hypothalamus : Considered specifically as an endocrine structure, the hypothalamus is ectodermal in origin and located at the floor of the diencephalon; its major endocrine job is controlling the secretory activity of the pituitary gland below it, through releasing hormones (RH) and inhibiting hormones (IH) -- all of them peptide hormones, and, because they are made by neurosecretory cells, also called neurohormones. Named hypothalamic hormones include Adrenocorticotropin Releasing Hormone (stimulates ACTH release by the anterior pituitary), Thyrotropin Releasing Hormone (stimulates TSH release), Gonadotropin Releasing Hormone/GnRH (stimulates the pituitary to secrete gonadotropins), Prolactin Inhibiting Hormone/prolactostatin (inhibits prolactin release), Somatostatin (inhibits growth-hormone release), Somatotropin-releasing hormone (stimulates growth-hormone release), and Gastrin Releasing Peptide (GRP) and Gastric Inhibitory Polypeptide (GIP). Separately, the hypothalamus is also the direct source of the two hormones stored and released by the posterior pituitary, ADH and oxytocin, covered under the neurohypophysis below. …