Double parathyroid adenoma, a clinically nondistinct entity of primary hyperparathyroidism

Double parathyroid adenoma (DA) has been suggested to be a clinically distinct entity of primary hyperparathyroidism (HPT). Altogether 659 patients with sporadic primary HPT were analyzed retrospectively by evaluating consecutive primary operations for more than three decades. Patients with postoperatively persistent HPT and those with incomplete medical, operative, or histologic records were disregarded. The mean age (+/- SD) at surgery was 60.9 +/- 12.7 years; 78% of the patients were female; and the duration of postoperative follow-up averaged 7.8 +/- 7.2 years. DA, defined as two enlarged parathyroid glands, was found in 77 patients (12%). Enlargement of a single gland (SA) or three or more glands (MA) occurred in 80% and 8%, respectively. DAs were bilateral in 72% of patients, and the weight of the two glands differed by 317 +/- 407 mg. The three histologic subgroups of patients exhibited no significant discrepancy with respect to age, classic symptoms of HPT, proportion of overtly asymptomatic individuals, or parathyroid tissue weight. A lower female predominance and extent of hypercalcemia and higher preoperative serum creatinine level occurred with DA and MA compared to SA. SA and DA differed from MA with respect to variably strong trends to lower postoperative incidences of recurrent HPT and hypoparathyroidism. DA seems to comprise an underrated histologic cause of HPT, which is eligible for a conservative operative approach. Clinical characteristics consistent with a distinct entity of sporadic primary HPT were not seen.