Pituitary tumors
Pituitary tumors: Excerpt from Handbook of Diseases
Constituting 10% of intracranial neoplasms, pituitary tumors typically originate 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. Some are part of a hereditary disorder called multiple endocrine neoplasia 1. Pituitary tumors aren’t malignant in the strict sense; however, because their growth is invasive, they’re considered a neoplastic disease.
Chromophobe adenoma may be associated with the 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 features.
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; signs and symptoms include amenorrhea, decreased libido and impotence in men, skin changes (waxy appearance, decreased wrinkles, and pigmentation), loss of axillary and pubic hair, lethargy, weakness, increased fatigability, intolerance to cold or heat, 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
❑ Magnetic resonance imaging (MRI), cranial computed tomography (CT) scanning, or skull X-rays with tomography show enlargement of the sella turcica or erosion of its floor; if growth hormone secretion predominates, X-ray films show enlarged paranasal sinuses and mandible, thickened cranial bones, and separated teeth. MRI and CT scan show the location and size of the adenoma.
❑ Carotid angiography shows displacement of the anterior cerebral and internal carotid arteries if the tumor mass is enlarging; it also rules out intracerebral aneurysm.
❑ Cerebrospinal fluid analysis may show increased protein levels.
❑ Endocrine function tests may contribute helpful information, but results are often ambiguous and inconclusive.
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. (See Transsphenoidal pituitary surgery.) 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 bromo-criptine, an ergot derivative that shrinks prolactin-secreting and growth hormone-secreting tumors. Antiserotonin drugs 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 transsphenoidal route) is a promising alternative to surgical dissection of the tumor.
Special considerations
❑ Conduct a comprehensive health history and physical assessment to establish the onset of neurologic and endocrine dysfunction and provide baseline data for later comparison.
❑ Make sure that the patient and his family understand that the patient needs lifelong evaluations and, possibly, hormone replacement.
❑ Reassure the patient that some of the distressing physical and behavioral signs and symptoms caused by pituitary dysfunction (for example, altered sexual drive, impotence, infertility, loss of hair, and emotional lability) will disappear with treatment.
❑ Maintain a safe, clutter-free environment for the visually impaired or acromegalic patient. Reassure him that he’ll probably recover his sight.
❑ Position patients who have undergone supratentorial or transsphenoidal hypophysectomy with the head of the bed elevated about 30 degrees to promote venous drainage from the head and reduce cerebral edema. (See Postcraniotomy care.)
❑ Place the patient on his side to allow drainage of secretions and prevent aspiration.
❑ Don’t allow a patient who has had transsphenoidal surgery to blow his nose.
❑ Watch for cerebrospinal fluid drainage from the nose. Monitor for signs of infection from the contaminated upper respiratory tract.
❑ Make sure that the patient understands that he’ll lose his sense of smell.
❑ Regularly compare the patient’s postoperative neurologic status with your baseline assessment.
❑ Monitor intake and output to detect fluid imbalances.
❑ Before discharge, encourage the patient to wear a medical identification bracelet or necklace that identifies his hormone deficiencies and their proper treatment.
Pictures
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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