The Pituitary Gland and Its Hormones

The pituitary gland, situated in the sella tursica and connected to the hypothalamus, is divided into the adenohypophysis (anterior pituitary) and neurohypophysis (posterior pituitary). The adenohypophysis comprises pars distalis and pars intermedia, though in humans, the pars intermedia is largely merged with pars distalis. The neurohypophysis stores and releases hormones synthesized by the hypothalamus.

The pars distalis (anterior pituitary) produces growth hormone (GH), prolactin (PRL), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH), and follicle stimulating hormone (FSH). The pars intermedia secretes melanocyte stimulating hormone (MSH).

GH regulates growth; over-secretion causes gigantism or acromegaly, while low secretion leads to pituitary dwarfism. Prolactin stimulates mammary gland growth and milk formation. TSH stimulates thyroid hormone synthesis and secretion. ACTH triggers glucocorticoid secretion from the adrenal cortex. LH and FSH, collectively called gonadotrophins, regulate gonadal activity; LH in males stimulates androgen synthesis and in females induces ovulation and maintains the corpus luteum, while FSH in males, along with androgens, regulates spermatogenesis and in females stimulates ovarian follicle development. MSH controls skin pigmentation.

The neurohypophysis stores and releases oxytocin and vasopressin (ADH), which are synthesized in the hypothalamus. Oxytocin stimulates uterine contractions during childbirth and milk ejection. Vasopressin acts on the kidneys to reabsorb water and electrolytes, reducing water loss through urine. Impaired synthesis or release of ADH leads to Diabetes Insipidus, characterized by excessive water loss and dehydration.