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Pituitary Adenomas

Background

Pituitary adenomas are the most common tumors of the pituitary gland, and are the fourth most common intracranial tumor after metastases, gliomas and meningiomas.

Over 90% of pituitary adenomas are benign, slow growing tumors. Less than 1% qualify are truly malignant, but even benigng tumors can often be problematic, causing pituitary dysfunction and blindness.

Aboout 15% of people will develop a pituitary adenoma over their lifetimes, but most of these never become symptomatic.

Pituitary adenomas are classified by size and whether they produce pituitary hormones:

     Microadenomas are less than 1 cm in diameter.

     Macroadenomas are over 1 cm in diameter.

Adenomas that produce excessive hormones include:

Prolactinomas: which secrete prolactin

Adrenocorticotropic hormone (ACTH) secreting adenomas causing Cushing’s Disease.

Growth hormone (GH) secreting adenomas causing Acromegaly.

Thyroid stimulating hormone (TSH) secreting adenomas causing hyperthyroidism.

Only 5% of pituitary adenomas are found as part of MEN (multiple endocrine neoplasia) syndromes, which are inherrited, autosomal dominant genetic conditions. The rest are the result of spontaneous mutation.

Evaluation

Pituitary adenomas become symptomatic through hormonal hypersecretion, destruction of normal pituitary function, pressure on the optic nerves causing vision loss and bleeding or swelling causing headache.

  • Hormonal hypersecretion: The three most common hormonally active adenomas are Prolactinomas, GH-Secreting Tumors causing Acromegaly, and ACTH-secreting tumors causing Cushing’s Disease. Thyroid stimulating hormone (TSH) tumors are relatively rare.
  • Pituitary destruction (Hypopituitarism): Larger tumors (macroadenomas) can damage the normal pituitary gland, causing hypogonadism (sexual dysfunction, loss of libido, and impotence), Hypothyroidism (fatigue, weakness, weight gain, coarse dry hair and dry skin, cold intolerance, depression), Adrenal Insufficiency (fatigue, weakness, loss of appetite, dizziness, nausea and vomiting), growth failure (in children and adolescents), and diabetes insipidus, with frequent urination and thirst. Hyperprolactinemia can also result from destruction of the pituitary stalk, another cause of hypogonadism.
  • Neurological problems: Larger pituitary macroadenomas can press on the optic pathways, causing tunnel vision or loss of peripheral vision, double vision or even loss of acuity with difficulty reading. This is a common initial symptom leading to the diagnosis of a pituitary macroadenoma.
  • Headache: Patients with macroadenomas often have headaches, most commonly on the front and sides of the head.
  • Bleeding (pituitary apoplexy): sudden bleeding in a pituitary ademoma or sudden death of the pituitary can cause headache, nausea, visual loss, double vision and confusion, all developing over a period of one to two days after the event. Studies will often confirm pituitary insufficiency.

Radiologic workup:

  • MRI of the pituitary gland with and without gadolinium. At the Tulsa Brain Tumor Clinic we have as a partner the only state of the art 3T MRI in Tulsa, allowing much better visualization of the disease.
  • CT scan can be helpful in showing the bony destruction around the pituitary fossa, the bony cup at the base of the skull in which the pituitary gland sits.

Hormonal Testing: This testing is extensive and complex. It should be managed by a board-certified endocrinologist. Hormone levels tested include:

  • ACTH
  • cortisol
  • LH (luteinizing hormone)
  • FSH and estradiol in women
  • testosterone in men
  • GH (growth hormone)
  • IGF-1
  • prolactin
  • free T4 (thyroid function)
  • TSH

Visual Testing:

Patients with visual complaints or patients whose tumors impinge on the optic pathways on MRI should undergo visual acuity testing and formal visual field testing.

Treatment

  • Endonasal Endoscopic Surgery:  The first-line treatment for most pituitary adenomas is endonasal transsphenoidal surgery. The Endonasal endoscopic approach the preferred method for removal of the great majority of pituitary adenomas, RCCs, most craniopharyngiomas and chordomas as well as many midline meningiomas. Rates of cure are in the 85% range for microadenomas, and in the 50% range for larger or invasive tumors. Complications can include added visual impairment,  bleeding, stroke, cerebrospinal fluid leak and meningitis, but these risks are low when performed by experienced board-certified neurosurgeons.
  • Cyberknife Radiosurgery: While radiosurgery is traditionally reserved for patients who are not operative candidates, or in whom surgery has been ineffective, results of radiosurgery are excellent, with control rates of 90% in a recent review of the literature. The risk of complications is lower than with surgery, and the risk of visual damage is less than with traditional radiation.
  • Medical and Radiation therapies: Please see specific tumor types. Acromegaly, Cushing’s Disease, Prolactinoma, Endocrine-Inactive.

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Comprehensive Brain Tumor Care and Pituitary Disorders Program