In some cases, enlargement of the pituitary is due to hyperplasia (increase in the number of cells), which may be a response to low levels of hormones from other glands (for example, low levels of thyroid hormone from the thyroid gland cause the pituitary to enlarge in order to produce more thyroid stimulating hormone ). The pituitary also normally enlarges during pregnancy due to hyperplasia. These causes of enlargement rarely cause symptoms.
In other cases, an enlarged pituitary gland may cause symptoms such as headaches. Because the growing gland often presses on the optic nerve, which passes above the pituitary gland, loss of vision may occur. Vision loss often initially affects only the upper, outermost fields of vision in both eyes.
Underproduction or overproduction of pituitary hormones may also occur.
Diagnosis is by computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more (CT) or magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRI). Pituitary function is checked by measuring hormone levels in the blood.
Treatment depends on the cause of the enlargement. For example, if enlargement is due to a tumor, the tumor may be treated with surgery, radiation therapy, or drugs, depending on the type of tumor, its size, and the symptoms it causes.
(See also Overview of the Pituitary Gland Overview of the Pituitary Gland The pituitary is a pea-sized gland that is housed within a bony structure (sella turcica) at the base of the brain. The sella turcica protects the pituitary but allows very little room for expansion... read more .)