The pituitary gland

The pituitary sits in a small bony pocket of the skull, the sella turcica, and hangs from the hypothalamus by a stalk. It has two main parts: the adenohypophysis (with the pars distalis, the front part, and the pars intermedia) and the neurohypophysis (pars nervosa, the back part).

• The pars distalis (anterior pituitary) makes six hormones: GH (growth hormone), prolactin, TSH (thyroid stimulating hormone), ACTH (adrenocorticotrophic hormone), LH (luteinising hormone) and FSH (follicle stimulating hormone).
• The pars intermedia makes one: MSH (melanocyte stimulating hormone). In humans it is almost merged with the pars distalis.
• The posterior pituitary does not make hormones; it stores and releases two hormones made in the hypothalamus: oxytocin and vasopressin.

What they do:

• GH: controls growth. Too much in children causes gigantism (very tall); in adults it causes acromegaly (the bones of the face, hands and feet thicken, disfiguring the face). Too little in childhood causes pituitary dwarfism.
• Prolactin: growth of the mammary glands and milk production.
• TSH: makes the thyroid release its hormones.
• ACTH: makes the adrenal cortex release glucocorticoids.
• LH and FSH (gonadotrophins), which act on the sex organs. In males, LH makes the testes make androgens, and FSH together with androgens controls sperm production. In females, LH triggers ovulation (release of the egg from the graafian follicle) and keeps up the corpus luteum, and FSH makes the follicles in the ovary grow.
• MSH: controls skin pigmentation (colour).
• Oxytocin: makes smooth muscles contract, especially the uterus during childbirth, and causes milk to be released from the mammary glands.
• Vasopressin (ADH): makes the kidney reabsorb water, reducing urine. If too little is made, the body loses too much water in dilute urine: diabetes insipidus.