Function

The pituitary is an endocrine gland secreting a number of hormones that regulate many bodily processes including growth, reproduction, and other metabolic activities. It is often referred to as the “master gland of the body.”

Hormones are secreted in the following lobes: Intermediate lobe: In cold-blooded animals, intermedin is secreted, influencing the activity of pigment cells (chromatophores) of fishes, amphibians, and reptiles. In warm-blooded animals, no effects are known.

Anterior lobe: Secretions here are the somatotropic, or growth hormone (STH or GH), which regulates cell division and protein synthesis for growth; adrenocorticotropic hormone (ACTH), which regulates functional activity of the adrenal cortex; thyrotropic hormone (TTH or TSH), which regulates functional activity of the thyroid gland; and prolactin, also called lactogenic hormone, which induces secretion of milk in the adult female. The gonadotropic hormones are as follows: in women, follicle-stimulating hormone (FSH) stimulates development of ovarian follicles and their secretion of estrogen; in men, it stimulates spermatogenesis in the testes. In women, luteinizing hormone (LH) stimulates ovulation and formation of the corpus luteum and its secretion of estrogen and progesterone. In men, LH also called interstitial cell-stimulation hormone (ICSH), stimulates testosterone secretion.

Posterior lobe: Hormones are secreted by the neurosecretory cells of the hypothalamus and pass through fibers of the supraopticohypophyseal tracts in the infundibular stalk to the neurohypophysis, where they are stored. Secretions here are oxytocin, which acts specifically on smooth muscle of the uterus, increasing tone and contractility, and antidiuretic hormone (ADH), which increases reabsorption of water by the kidney tubules. In large amounts, ADH also causes vasoconstriction, and is also called vasopressin.

Disorders

Hypersecretion of anterior lobe causes gigantism, acromegaly, and pituitary basophilism (Cushing disease). Hyposecretion of anterior lobe causes dwarfism, pituitary cachexia (Simmonds disease), Sheehan syndrome, acromicria, eunuchoidism, or hypogonadism. Posterior lobe deficiency or hypothalamic lesion causes diabetes insipidus. Anterior and posterior lobe deficiency and hypothalamic lesion cause Fröhlich syndrome (adiposogenital dystrophy) and pituitary obesity.

Salivary secretion is under nervous control, reflexly initiated by mechanical, chemical, or radiant stimuli acting on taste buds in the mouth, olfactory receptors, or the eyes. Secretion may also be due to conditioned reflexes as when one thinks about food or hears a dinner bell. The nerve supply of the salivary glands is from the facial and glossopharyngeal nerves, which increase secretion, and from the sympathetic nerves, which decrease secretion. The blood supply is from branches of the external carotid artery.