The pituitary gland is a very small gland located roughly at the back of the spine at the base of the neck. Starting at puberty, it releases human growth hormone, which causes the body to grow quickly and also triggers the sex organs (testicles and ovaries) to produce more sex hormones to bring on secondary sexual characteristics. In normal persons, the hormone stops being released, except in minor quantities, after a person reaches adulthood.
Several conditions can result from a the misfunction of the pituitary:
A lack of the hormone in adolescence can lead to hypopituitary disease or short stature although the patient's proportions are normal (i.e. a midget).
A surplus of the hormone in adolescence can lead to hyperpitutitary disease or gigantism; the patient grows to a very large height, usually in excess of 7ft in males and 6'6" in females, although they stop growing once they reach adulthood.
If the hormone continues being produced into adulthood, the result is acromegaly; the patient continues to grow in height and weight during their lifetime, taking on an appearance distinctive of the disease, such as a lantern-shaped draw. Perhaps the best known person with this disorder was professional wrestler Andre the Giant. Acromegaly patients generally have greatly lessened life spans.
The pituitary also governs kidney function, and an injury to the gland can lead to diabetes insipidus, where the kidneys constantly process urine even though there is no need to remove waste products from the body.