Benign pituitary adenomas.

These tumors, which are benign, make up 7 to 10 percent of primary brain tumors. They appear in middle age, more often in women than men. Problems caused by these growths are related to endocrine abnormalities caused by either reduced or excessive levels of hormones controlled by the pituitary gland. This gland, which is located near the base of the brain, secretes a number of hormones that have an effect upon other endocrine glands. It is often referred to as the master endocrine gland, because its hormones are instrumental both in growth and metabolism and in controlling other endocrine glands.

The tumor's encroachment on adjacent structures, particularly the optic nerve, is common. Slow enlargement of these tumors erodes the delicate bony structures that surround the normal gland. X rays of the skull, with particular attention to the pituitary area, and precise examination of the patient's field of vision are the key diagnostic tests for tumors that have attained moderate size. CT scans are also useful, as are blood hormonal studies. Hormonal changes are often present and can occur before any other manifestation of abnormality in the size of the pituitary gland. Spinal puncture is not done because it usually does not contribute any relevant findings.

Symptoms are related to hormonal imbalances caused by the tumor, and they point to the tumor's particular cell type. Acromegaly (or gigan-tism) indicates high levels of growth hormones, Cushing's disease points to excessive steroid hormones, and inappropriate production of breast milk indicates high prolactin levels. Enlargement of the gland by a tumor of one cell type can result in oversecretion of its hormone and under-secretion of others.

Pituitary tumors can extend outside its protective cavity (the sella) and sometimes enlarge rapidly because of bleeding within the body of the tumor. On the other hand, many small pituitary growths that produce little or no abnormality in hormonal function are never diagnosed, remaining silent forever.

Treatment of pituitary adenomas is complex. The oversecretion of some hormones must be controlled while appropriate replacement therapy of undersecreted hormones must be instituted. For example, suppression of ACTH (adrenocortico-stimulating hormone) and TSH (thyroid-stimulating hormone) will result in dangerously low levels of steroids and thyroid hormone respectively. Accurate laboratory testing is widely available and replacement programs have been well defined. Surgical treatment, either via the side of the skull or through the back of the nose, may be performed to stop oversecretion of certain hormones and to prevent blindness from fast-growing tumors. Lifelong replacement therapy of thyroid, corticosteroid, and perhaps gonadal hormones is almost always needed after surgery. Radiation therapy is an alternative to surgery; it produces a slower result with some chance of treatment failure, but avoids the risk of surgery. Radiation therapy may be the treatment of choice for small, nonsecreting tumors but is not advisable for tumors that have grown outside the normal confines of the pituitary.