Pituitary Tumors

Constituting 10% of intracranial neoplasms, pituitary tumors originate most often in the anterior pituitary (adenohypophysis). They occur in adults of both sexes, usually during the third and fourth decades of life, The three tissue types of pituitary tumors are chromophobe adenoma (90%), basophil adenoma, and eosinophil adenoma.

The prognosis is fair to good, depending on the extent to which the tumor spreads beyond the sella turcica.

Causes

Although the exact cause is unknown, a predisposition to pituitary tumors may be inherited through an autosomal dominant trait. Pituitary tumors aren't malignant in the strict sense, but because their growth is invasive, they're considered a neoplastic disease.

Chromophobe adenoma may be associated with production of corticotropin, melanocyte-stimulating hormone, growth hormone, and prolactin; basophil adenoma, with evidence of excess corticotropin production and, consequently, with signs of Cushing's syndrome; and eosinophil adenoma, with excessive growth hormone.

Signs and symptoms

As pituitary adenomas grow, they replace normal glandular tissue and enlarge the sella turcica, which houses the pituitary gland. The resulting pressure on adjacent intracranial structures produces typical clinical manifestations

Neurologic features .

• Frontal headache
• Visual symptoms, beginning with blurring and progressing to field cuts (hemianopias) and then unilateral blindness
• Cranial nerve involvement (III, IV, VI) from lateral extension of the tumor, resulting in strabismus; double vision,
  with compensating head tilting and dizziness; conjugate deviation of gaze; nystagmus; lid ptosis; and limited eye movements
• Increased intracranial pressure (secondary hydrocephalus)
• Personality changes or dementia, if the tumor breaks through to the frontal lobes
• Seizures
• Rhinorrhea, if the tumor erodes the base of the skull
• Pituitary apoplexy secondary to hemorrhagic infarction of the adenoma. Such hemorrhage may lead to both cardiovascular and adrenocortical collapse.

Endocrine features

• Hypopituitarism, to some degree, in all patients with adenoma, becoming more obvious as the tumor replaces normal gland tissue; symptoms include amenorrhea, decreased libido and impotence in men, skin changes (waxyappearance, decreased wrinkles, and pigmentation), loss of axillary and pubic hair, lethargy, weakness, increased fatigability, intolerance to cold, and constipation (because of decreased corticotropin and thyrotropin production)
• Addisonian crisis, precipitated by stress and resulting in nausea, vomiting, hypoglycemia, hypotension, and circulatory collapse
• Diabetes insipidus, resulting from extension to the hypothalamus
• Prolactin-secreting adenomas (in 70% to 75%), with amenorrhea and galactorrhea; growth hormone-secreting adenomas, with acromegaly; and corticotropin-secreting adenomas, with Cushing's syndrome.

Diagnosis

Doctors can detect larger pituitary tumors on an x-ray, computerized tomography scan or magnetic resonance scan. Many pituitary tumors, however, are too small to be seen on these images of the pituitary region of the brain. To diagnose these tumors, doctors try to detect the hormonal abnormalities with various tests. Often blood or urine levels of specific hormones are measured within a few hours of giving the patient compounds known to stimulate or suppress production of the hormones.

For instance, sometimes patients are given a glucose tolerance test. After fasting overnight, the patient drinks a sugar solution, then has blood samples taken in which sugar or growth hormone levels are measured. Sometimes, in order to locate a very small tumor in the pituitary gland, an invasive procedure is required. This procedure is called inferior petrosal sinus sampling. A radiologist inserts special catheters from the groin veins into the vessels that drain the pituitary gland at the top of the neck and draws blood for measurement of the hormone that the tumor secretes.

Treatment

Surgical options include transfrontal removal of large tumors impinging on the optic apparatus and transsphenoidal resection for smaller tumors confined to the pituitary fossa. Radiation is the primary treatment for small, nonsecretory tumors that don't extend beyond the sella turcica and for patients who may be poor postoperative risks; otherwise, it's an adjunct to surgery.

Postoperative treatment includes hormone replacement with cortisone,thyroid, and sex hormones; correction of electrolyte imbalance; and, as necessary, insulin therapy.

Drug therapy may include bromocriptine, an ergot derivative that shrinks prolactin-secreting and growth hormonesecreting tumors. Cyproheptadine, an antiserotonin drug, can reduce increased corticosteroid levels in the patient with Cushing's syndrome.

Adjuvant radiotherapy is used when only partial removal of the tumor is possible. Cryohypophysectomy (freezing the area with a probe inserted by trans sphenoidal route) is a promising alternative to surgical dissection of the tumor.

Radiation therapy can provide long-term control of the disease if it recurs after surgery, and radioactive pellets can be implanted in the brain to treat craniopharyngiomas. CV205-502, a new dopamine agonist (a drug that increases the effect of another, in this instance dopamine) can control symptoms of patients who do not respond to proscription.

Coping skills

It's natural for you and your family to have many questions throughout diagnosis and treatment of a pituitary tumor. The process can be overwhelming - and frightening. That's why it might help to write down your questions and bring them with you to your appointments. As your doctor answers your questions, take notes or ask a family member to accompany you and take notes. The more you and your family know and understand about each aspect of your care, the better.