Background: Primary hyperparathyroidism (pHPT), typically defined as elevated serum calcium levels associated with inappropriately elevated parathyroid hormone (PTH) levels, can occur also in patients with normal serum calcium levels. This study investigated the characteristics, workup, and surgical management of patients with normocalcemic pHPT.
Methods: A retrospective chart review of a prospectively collected, single-institution parathyroid database was performed on patients with sporadic pHPT who underwent parathyroidectomy between 12/99 and 12/08.
Results: In all, 93 of 771 (12%) pHPT patients had normal serum calcium levels 3 months prior to surgery. Ionized calcium (iCa) levels were available for 58 patients and were elevated in 50 (86%). Among those with elevated iCa levels 90% had single-gland disease (SGD), whereas 63% with normal iCa levels had SGD (p = 0.07). Preoperative imaging identified SGD in 60% of patients with normal iCa and in 66% with elevated iCa levels. Intraoperative PTH (IOPTH) monitoring identified cure in 51 of 58 (88%) patients including 6 (75%) with normal iCa. At a median follow-up of 358 days, postoperative calcium and PTH levels were similar in the groups. One (1%) patient had recurrent disease.
Conclusions: Most patients with apparent normocalcemic pHPT have elevated ionized calcium levels. For patients with normocalcemic pHPT, we recommend measuring iCa levels preoperatively, performing localization studies, and utilizing IOPTH monitoring to guide a successful operation.