Multiple Endocrine Neoplasia

Three distinct syndromes of multiple endocrine neoplasia have been described.1 Type 1 is characterized by adenomas or diffuse hyperplasia of the parathyroid glands, the pituitary, and the endocrine pancreas. Thyroid lesions have also been described, but they are not uniformly present and may be coincidental. Hyperfunction of the adrenal cortex occurs in a minority of patients; it is probably secondary to true Cushing's disease or to ectopic hormone secretion by neoplastic islet cells or by small-cell (carcinoid-like) tumors of the mediastinum. Patients with type 2 (or 2A) or 3 (or 2B) have medullary thyroid carcinoma and pheochromocytoma, and hyperparathyroidism develops . . .