Multiple endocrine neoplasia
Multiple endocrine neoplasia: Excerpt from Professional Guide to Diseases (Eighth Edition)
Multiple endocrine neoplasia (MEN) is a hereditary disorder in which two or more endocrine glands develop hyperplasia, adenoma, or carcinoma, concurrently or consecutively. Two of the types that occur are well documented: MEN I (Werner’s syndrome) involves hyperplasia and adenomatosis of the pituitary and parathyroid glands, islet cells of the pancreas and, rarely, the thyroid and adrenal glands; MEN II (Sipple’s syndrome) involves medullary carcinoma of the thyroid, with hyperplasia and adenomatosis of the adrenal medulla (pheochromocytoma) and parathyroid glands. MEN I is the most common form.
Causes and incidence
MEN usually results from autosomal dominant inheritance. It affects males twice as often as females and may occur at any time from adolescence to old age, but is rare in children.There’s no racial predilection.
Signs and symptoms
Clinical effects of MEN may develop in various combinations and orders, depending on the glands involved. The most common manifestation of MEN I is hyperparathyroidism, followed by ulcer due to Zollinger-Ellison syndrome (marked by increased gastrin production from non-beta islet cell tumors of the pancreas). Hypoglycemia may result from pancreatic beta islet cell tumors, with increased insulin production. When MEN I affects the parathyroids, it produces signs of hyperparathyroidism, including hypercalcemia (because the parathyroids are primarily responsible for the regulation of calcium and phosphorus levels). When MEN causes pituitary tumor, it’s most commonly a prolactinoma, but can be a growth hormone or corticotropin, or even a nonsecretory adenoma.
Characteristic features of MEN II with medullary carcinoma of the thyroid include enlarged thyroid mass, with resultant increased calcitonin and, occasionally, ectopic corticotropin, causing Cushing’s syndrome. With tumors of the adrenal medulla, symptoms include headache, tachyarrhythmias, and hypertension; with adenomatosis or hyperplasia of the parathyroids, symptoms result from renal calculi.
Diagnosis
Investigating symptoms of pituitary tumor, hypoglycemia, hypercalcemia, or GI hemorrhage may lead to a diagnosis of MEN. Diagnostic tests must be used to carefully evaluate each affected endocrine gland. For example, radioimmunoassay showing increased levels of gastrin in patients with peptic ulceration and Zollinger-Ellison syndrome suggests the need for follow-up studies for MEN I because 50% of patients with Zollinger-Ellison syndrome have MEN. After confirmation of MEN, family members must also be assessed for this inherited syndrome.
Magnetic resonance imaging or computed tomography scan of the abdomen may show pancreatic tumor. Insulin test may show increased levels and fasting blood sugar may be low.
Treatment
Treatment must eradicate the tumors. Subsequent therapy controls residual symptoms. In MEN I, peptic ulceration is usually the most urgent clinical feature, so primary treatment emphasizes control of bleeding or resection of necrotic tissue. In hypoglycemia caused by insulinoma, oral administration of diazoxide or glucose can keep blood glucose levels within acceptable limits. Subtotal (partial) pancreatectomy is required to remove the tumor. Because all parathyroid glands have the potential for neoplastic enlargement, subtotal parathyroidectomy may also be required along with transsphenoidal hypophysectomy. In MEN II, treatment of an adrenal medullary tumor includes antihypertensives and resection of the tumor. Bromocriptine may be used for pituitary tumors that secrete prolactin. Hormonal replacement therapy is necessary when glands are removed or secretion is inadequate.
Special considerations
Supportive care depends on the body system involved.
❑ If MEN involves the pancreas, monitor blood glucose levels frequently. If it affects the adrenal glands, monitor blood pressure closely, especially during drug therapy.
❑ Manage peptic ulcers, hypoglycemia, and other complications, as needed.
❑ If pituitary tumor is suspected, watch for signs of pituitary trophic hormone dysfunction, which may affect any of the endocrine glands. Also, be aware that pituitary apoplexy (sudden severe headache, altered level of consciousness, visual disturbances) may occur.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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