Parathyroidectomy for Normocalcemic Tertiary Hyperparathyroidism: A 19-Year Experience

Parathyroidectomy is the standard management for patients with tertiary hyperparathyroidism (THPT) and hypercalcemia. However, a subset of patients with THPT have normal or mildly-elevated serum calcium levels in the setting of significantly elevated parathyroid hormone (PTH). The purpose of this study is to determine the effectiveness and safety of parathyroidectomy in normocalcemic THPT.

Retrospective review of 212 consecutive patients with THPT who subsequently underwent parathyroidectomy between 2001 and 2020 was performed. Patients were categorized as normocalcemic, "mild" (Ca ≤ 10.4 mg/dL) or hypercalcemic, "classic" THPT (Ca ≥ 10.5 mg/dL) and clinical data are compared.

71 of 212 (34%) were normocalcemic with median pre-operative Ca and PTH levels of 9.7 mg/dL and 225pg/mL, respectively and 141 of 212 (67%) were hypercalcemic with median preoperative Ca and PTH levels of 11 mg/dL and 211pg/mL, respectively. The mean length of stay was shorter in normocalcemic patients (0.33 versus 0.50 d; P = 0.03). 10 of 71 (14%) normocalcemic patients underwent reoperative parathyroidectomy, more than double that of hypercalcemic patients (5.6%; P = 0.06). Concomitant thymectomy was performed in 28.1% and 22.1% of normocalcemia and hypercalcemic patients, respectively (P = 0.44). No patient in either group required intravenous calcium or had undetectable PTH levels, but permanent hypocalcemia was more frequent in normocalcemic compared to hypercalcemic patients (11.2% versus 1.4%; P = 0.03).

Parathyroidectomy for normocalcemic tertiary hyperthyroidism (HPT) can be performed safely. These data can help guide multidisciplinary discussions for earlier surgical referral and intervention. Future investigations are needed to evaluate the impact of parathyroidectomy on the renal allograft, bone health, and cardiovascular disease.