Pituitary Tumors

PITUITARY TUMORS

All patients with pituitary tumors need to be evaluated by an endocrinologist, especially prior to considering a surgical procedure. Since pituitary disorders are some of the most complex of any endocrine problems, it is very important that the treating endocrinologist have a strong background in the diagnosis and treatment of pituitary diseases.

Up to 10% of patients undergoing MRI of the brain are found to have small pituitary cysts or tumors that are clinically asymptomatic. Most of these are small (< 10mm) and hormonally inactive. They usually do not disrupt the normal function of the pituitary gland or cause problems with surrounding structures. However, some pituitary tumors are problematic. Differentiating the pituitary tumor that is harmless from one that may cause a problem is not always an easy process. When pituitary tumors cause problems, they do so through mass effects of through hormonal dysfunction.

Mass Effects

Pituitary tumors that are < 10 mm are called microadenomas, whereas tumors that are 10 mm are called macroadenomas, Macroadenomas are more likely to cause damage to surrounding structures because of their size. If the pituitary tumor grows upward, it can damage the optic nerves and result in visual impairment or blindness. Large pituitary masses can also press on the brain, invade blood vessels or the sinus cavities. Large pituitary tumors may overproduce pituitary hormones or impair normal pituitary function. Patients may have a variety of symptoms including visual impairment, headache, or symptoms for overproduction or underproduction of pituitary hormones.

Hormonal Overproduction

Pituitary tumors are usually not hormonally active. However they may overproduce a variety of pituitary hormones. These include prolactin (loss of menstrual cycles, infertility, breast milk production in women or low libido and impotence in men), ACTH (Cushing’s disease), growth hormone (acromegaly) or TSH (hyperthyroidism). Prolactin-secreting pituitary adenomas are by far the most common.

Hormonal Underproduction

Some pituitary tumors may damage the neighboring cells in the pituitary and impair normal pituitary function. One or more of the pituitary hormones may be affected when this occurs. Loss of LH or FSH results in loss of menstrual cycles or infertility in women and impaired libido, erectile dysfunction or infertility in men. Impaired secretion of other pituitary hormones can also be seen: TSH deficiency (hypothyroidism), growth hormone deficiency, ACTH deficiency (adrenal insufficiency) or AVP deficiency (frequent urination / increased thirst – diabetes insipidus).

Endocrine Evaluation

An endocrine evaluation begins with proper imaging of the pituitary using high quality imaging protocols (usually MRI) in collaboration with an experienced neuroradiologist. The endocrinologist will arrange for testing of various pituitary hormones and assessment of associated endocrine organs in a series of blood, urine and saliva tests. In some cases stimulation or suppression tests will be necessary. Such tests are especially critical before and after surgical procedures on the pituitary. The tumor will be monitored over time in terms of its size and its affect on various pituitary hormones.

Treatment

In general, microadenomas are usually not surgically resected if they are hormonally silent. Large tumors that are causing a mass-effect usually require surgery. This may be done transphenoidally (through the nose and sinus cavity) or transcranially (through the side of the head). When surgery fails to control overproduction of pituitary hormones, medication is used to regulate the situation. In some cases the patient is also treated with radiation therapy or gamma knife therapy. This is also true of tumors that cannot be completely removed with surgery. Many pituitary tumors respond well to medications (especially prolactin-secreting tumors) and may not require surgical resection.

When the pituitary tumor, or surgery to remove it results in underproduction of pituitary hormones, the endocrinologist will provide replacement therapy of the deficient hormones (thyroid hormone, testosterone, estrogen, steroids, growth hormone, etc.)