Hypercalcemia in the multiple endocrine neoplasia syndromes.

Multiple endocrine neoplasia includes disorders with hyperfunction of two or more endocrine tissues. In MEN type 1, hyperfunction of the parathyroid glands causing hypercalcemia is the most common clinical presentation. In vitro, suppression of parathyroid tissue by calcium is similar, but the set-point of hyperplastic tissue is shifted as compared with normal. The gene for MEN-1 has been localized to chromosome 11 and is linked to the basic fibroblast growth factor gene. Parathyroidectomy results in a high failure rate with recurrent hyperparathyroidism or autonomous graft function in autotransplanted tissue. Family screening is recommended once every 5 years in first-degree relatives. The approach to hyperparathyroidism in MEN-2 (2A) must be individualized during surgery for medullary thyroid carcinoma. Hyperparathyroidism in MEN-3 (2B) is often associated with normal serum calcium and may not require intervention.