Primary Adenoma Arising From Two Ipsilateral Supernumerary Inferior Parathyroid Adenomas

A single parathyroid adenoma is the most common cause of primary hyperparathyroidism (PHPT). However, multiple synchronous adenomas can be found at surgery. More uncommon are ipsilateral synchronous adenomas, and that combined with a supernumerary gland, is even more rare. Here we present a case of PHPT due to an ipsilateral double adenoma of the inferior parathyroid gland, which was supernumerary. The diagnosis was made preoperatively by ultrasonography; however, sestamibi scan showed only a single hyperfunctioning gland on the left side. This was further substantiated by the use of intraoperative parathyroid hormone (PTH) monitoring, wherein PTH levels decreased to less than 50% of preoperative values only after the complete removal of the second adenomatous gland. This case report highlights the importance of preoperative localization and intraoperative PTH monitoring in evaluating patients with PHPT in the setting of multiple synchronous parathyroid adenoma.