Abnormal growths in the pituitary gland, which may cause hormonal disturbances
The pituitary gland, located at the base of the brain, secretes hormones that either have a direct effect on the body or affect other hormone-secreting glands. For this reason, an abnormality in the pituitary gland may affect several body systems. Some pituitary tumours produce excessive amounts of hormones; others do not produce hormones themselves but can disrupt the production of hormones from adjacent cells.
Tumours of the pituitary gland are rare. Usually, tumours occur in the front part of the gland and are noncancerous. The cause of most pituitary tumours is not known, although rarely they may be associated with the inherited disorder multiple endocrine neoplasia.
Nearly half of all hormone-secreting pituitary tumours make excess prolactin. Increased levels of prolactin may lead to infertility in women and to erectile dysfunction in men (see Prolactinoma). Some pituitary tumours secrete growth hormone, causing enlargement of some parts of the body (see Acromegaly). Others secrete hormones that over-stimulate the adrenal glands, causing changes in body chemistry and physical appearance (see Cushing’s syndrome).
As it grows, any pituitary tumour may press against the optic nerves, which lie above the gland. Such compression may cause headaches and loss of part of the field of vision (see Visual field defects). Growing pituitary tumours may also damage surrounding cells, thereby reducing secretion of one or more pituitary hormones (see Hypopituitarism). Reduced secretion of thyroid-stimulating hormone (TSH) may cause hypothyroidism. A tumour that presses on the posterior part of the pituitary gland may reduce secretion of vasopressin, which controls water balance (see Diabetes insipidus).
You may have several blood tests to look for abnormal levels of pituitary hormones. You may also have MRI or CT scanning to look for a tumour and a visual field test to check for blind areas. In some instances, a pituitary tumour is discovered during tests for another disorder. In this case, the tumour may be monitored without treatment unless symptoms develop.
Some tumours are treated with drugs (see Pituitary drugs). Others must be removed surgically. If it is not possible to remove the whole tumour, radiotherapy may be given to prevent further growth of abnormal tissue. These treatments can result in hypopituitarism (underactivity of the pituitary), which may need hormone replacement for life.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.