Multiple Endocrine Neoplasia (MEN)

Multiple endocrine neoplasia (MEN) is a group of inherited disorders generally characterized by the development of tumors in multiple endocrine glands.  These tumors can be benign or malignant and can lead to a variety of hormonal imbalances.

Multiple endocrine neoplasia type 1 (MEN1) is caused by mutations in the MEN1 tumor suppressor gene and is characterized by tumors of the Parathyroid gland, Pituitary, and Pancreas (mnemonic: the "3 Ps") ( Table 1).

Primary hyperparathyroidism is often the initial manifestation and usually presents with asymptomatic hypercalcemia or renal stones.  Indications for parathyroidectomy in patients with MEN1, similar to those for sporadic primary hyperparathyroidism, include symptomatic hypercalcemia, end-organ complications (eg, osteoporosis, chronic kidney disease, nephrolithiasis), and an increased risk for complications (eg, urinary calcium excretion >400 mg/day).  Patients age <50 are likely to develop complications later in life and should also undergo parathyroidectomy; because MEN1 typically presents at a relatively young age, most patients should be offered surgery.  Patients with MEN1 usually have multiple parathyroid adenomas and therefore require subtotal (≥3½ glands) or total parathyroidectomy with autotransplant into a muscle pocket.