Pituitary disorders are characterized by an excess or deficiency in one or more of the hormones produced by the pituitary gland and/or by the symptoms caused by the compression of surrounding tissues when a pituitary tumor is present. The pituitary is a pea-sized gland located in the center of the head behind the sinus cavity. It is found at the bottom of the brain, below the hypothalamus. The hypothalamus and pituitary gland are part of the endocrine system, a group of glands that work together to produce and regulate hormones that affect tissues throughout the body. The hypothalamus communicates with the brain and nervous system. It senses the body’s need for a specific hormone and tells the pituitary when to initiate or increase production of that hormone.

The pituitary consists of an anterior and posterior portion. In the anterior portion, growth hormone (GH), adrenocorticotropin (ACTH), thyroid-stimulating hormone (TSH), lutenizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin are produced. These hormones help regulate bone growth, muscle mass, the body’s response to stress, blood sugar, the rate at which the body uses energy (metabolic rate), the development of secondary sexual characteristics, fertility, and milk production. They affect specific “target” tissues throughout the body, including the thyroid gland, adrenal glands, ovaries (women), and testes (men). In the posterior portion of the pituitary, oxytocin is produced and antidiuretic hormone (ADH, produced in the hypothalamus) is stored for release. ADH controls the amount of water that the kidneys excrete, which in turn helps regulate the balance of water in the body. Oxytocin stimulates the contraction of the uterus during and after childbirth and is responsible for stimulating the release of milk during breastfeeding.