A pituitary adenoma is a brain tumor that arises from the pituitary gland, which is located at the base of the brain, deep to the nasal cavity, and between the nerves that transmit information from the eyes to the brain.  The pituitary gland emits hormones (messenger proteins that tell specific parts of the body to increase or decrease their function); it controls the other glands in the body.  An adenoma in this location may disrupt the function of these chemical messengers, resulting in specific symptoms.  Pituitary tumors represent 10% of all tumors in the brain. 

Symptoms from a pituitary tumor vary, and depend upon its size, as well as whether the tumor itself produces hormones.  Symptoms may include enlargement of the breast tissue with production of milk, prevention or cessation of the menstrual cycle in a female, abnormal growth of the body (including the hands and face), gigantism, loss of sex drive, infertility, malfunction of regulation of salt and water excretion from the kidneys.  If the tumor becomes large enough, it may compress the optic nerves that transmit information from the eyes to the brain; in such cases, a patient may experience loss of parts of their peripheral vision as well as decreased visual acuity. 

Occasionally, a pituitary adenoma may bleed or enlarge quickly.  In such cases, vision may decrease significantly and rapidly.  Such an event represents an emergency, and the patient should seek medical attention immediately.

Pituitary adenomas are best evaluated on MRI, but may also be appreciated on CT.  On rare occasions, angiography is used to differentiate a bleeding tumor from an intracranial aneurysm.  Certain medications may be used to treat and shrink the tumor, especially if it makes certain hormones.  However, surgical resection is often used to provide a diagnosis and to excise the tumor.  Resection is most commonly performed through the nasal passages using long telescopes, called endoscopes, to see into the back of the nasal cavity.  Radiosurgery may also be used if the tumor encases vital structures. 

Justin F. Fraser, MD