Existence and anatomic distribution of double parathyroid adenoma

Double parathyroid adenomas occur in 2% to 15% of primary hyperparathyroidism cases, but the very existence of double adenomas has been controversial. This study was conducted to evaluate the clinical significance and anatomic distribution of parathyroid double adenomas.

Mono-institutional retrospective study of the medical records of 183 unselected consecutive patients who underwent intervention for primary hyperparathyroidism between 1996 and 2003.

A total of 14 (7.65%) patients were found to have double parathyroid adenomas. Intraoperative parathyroid hormone (PTH) levels were measured in every case. Two enlarged parathyroid glands were identified in four possible configurations: two both superior, one both inferior, two both right, three both left, two right superior and left inferior, and three left superior and right inferior. There was a preferential crossed bilateral distribution of double adenomas. In all patients, intraoperative PTH levels dropped by at least 50% from baseline after removal of both abnormal parathyroid glands. In this series, no patient developed persistent hypoparathyroidism or had recurrent laryngeal nerve injuries or neck hematoma. All patients remained normocalcemic 9 to 96 months postoperatively. One patient had persistently elevated PTH values with normal serum calcium levels.

The drop in intraoperative PTH levels and maintenance of normocalcemia postoperatively confirm previous reports that double adenomas do exist and are not simply missed cases of four-gland hyperplasia. There was a preferential crossed bilateral distribution of double adenomas in this series.