The pituitary gland is about the size of a pea, situated in a bony cavity at the base of the brain. Its function is to produce a number of hormones which regulate metabolic processes. Thus the pituitary gland controls growth, the quantity of water in the body, the formation of milk in the breasts, contraction of the womb during labour and the function of the thyroid, adrenal and sex glands. Disorders cause over- or under-production of one or more of these hormones, and can result from a pituitary tumour, or brain damage, although often the cause is unknown. Excess growth hormone production can cause gigantism or acromegaly, excess sex hormone (FSH and LH) early puberty, and too little fluid-regulating hormone (ADH) can lead to diabetes insipidus, in which the kidneys excrete too much water with the urine. If the pituitary gland fails completely, all the hormones are underproduced. Some of the symptoms are listlessness, fatigue, muscular weakness, weight loss, loss of libido, loss of armpit and pubic hair, and lack of menstruation in women. In children growth slows down. Treatment is aimed at restoring normal hormone levels in the blood. Excess production can be controlled by surgical removal of (part of) the pituitary gland, by radiation therapy or by drugs to suppress hormone production. If the pituitary gland fails, synthetic hormones can be supplied, by injection, tablets or nasal spray. In the last case the active substances reach the bloodstream via the nasal mucous membrane. Such treatment usually restores normal bodily function almost completely. Usually benign growth of certain cells in the pituitary gland. Symptoms are related to the function and site within the pituitary gland, which is about the size of a pea. Its function is to produce various hormones; a tumour can stop this process, or the cells of which the tumour consists can become hyperactive and produce a particular hormone in excessive quantities, usually with associated under-production of others. Excess growth hormone production can cause gigantism or acromegaly , and excess sex hormone (FSH and LH) can lead to early puberty; other effects depend on the site and size of the tumour. The pituitary gland is in a cavity at the base of the brain, near the intersection of the left and right optic nerves. A large tumour can exert pressure on these nerves, possibly causing blindness and persistent, increasingly severe headache. A pituitary tumour is diagnosed by measurement of certain blood-hormone levels; an X-ray of the skull shows enlargement of the pituitary cavity. Treatment is by surgery to remove the tumour, or radiation therapy. It is sometimes sufficient to check cells which are producing excess hormone using drugs.