Analyses of Predictive Factors Associated with Hypocalcemia and Elevated iPTH with Normocalcemia after Ultrasound-guided Radiofrequency Ablation for Primary Hyperparathyroidism

Abstract

Purpose To assess the feasibility of ultrasound-guided (US-guided) radiofrequency ablation (RFA) for primary hyperparathyroidism (PHPT) and determine predictive factors for hypocalcemia and elevated serum intact parathyroid hormone(ePTH) with normocalcemia after ablation. Materials and Methods Between January 2015 and January 2021, data from 44 patients with PHPT who were treated with US-guided RFA were retrospectively evaluated. Serum intact parathyroid hormone(iPTH), total calcium (Ca), phosphorus, alkaline phosphatase (ALP), and 25-hydroxyvitamin D3 (25(OH)D3) levels and the volume of the abnormal enlarged parathyroid glands were recorded before RFA. Changes in iPTH and Ca levels at 1 and 3 days, and, 1, 3, and 6 months after ablation were recorded. Results Overall, thirteen patients developed hypocalcemia 1–3 days after RFA. ePTH with normocalcemia developed in 17 patients 1 month after RFA. Thirty-two patients were followed up for more than 6 months, and 27 of these patients had sustained normalized values for both serum iPTH and Ca levels more than 6 months after RFA. There were significantly more patients who developed hypocalcaemia, when the baseline ALP was greater than 261.5 U/L (sensitivity 61.5%, specificity 100.0%). The risk of ePTH decreased by 21.7% for every 1 ng/mL increase in 25 (OH) D3. The risk of ePTH was increased when a patient's serum iPTH was higher than 172.4 pg/mL (sensitivity 88.2%, specificity 76.2%). Conclusions US-guided RFA is feasible for clinical management of PHPT patients. Hypocalcaemia following RFA was associated with higher pre-RFA serum ALP levels. Elevated iPTH levels with normocalcemia at 1 month after RFA were associated with pre-RFA vitamin D deficiency and higher baseline iPTH levels. Patients with higher serum ALP and iPTH and lower 25 (OH) D3 levels before RFA need to be managed carefully and monitored closely after RFA of PHPT.