Vitamin D3 Deficiency is Associated with Late-Onset Hypocalcemia After Minimally Invasive Parathyroidectomy in a Vitamin D Borderline Area

Concurrent vitamin D-3 deficiency is common in primary hyperparathyroidism (pHPT). We aimed to examine the clinicopathologic features and short-term outcomes of vitamin D-3-deficient patients after minimally invasive parathyroidectomy (MIP). Over 2-year period, 80 consecutive MIP patients had preoperative-fasting 25-hydroxyvitamin D-3 (25OHD(3)) checked. Forty-five patients had a 25OHD(3) level < 20 ng/ml and were defined as deficient. Intraoperative parathyroid hormone (IOPTH) assay was used for all MIP. Postoperative adjusted calcium (Ca) was checked at 6, 16 (with intact PTH), and 24 h. Oral calcium and vitamin D supplements were given if hypocalcemic symptoms developed or Ca < 2.00 mmol/l. Late-onset hypocalcemia (LOH) was defined as symptoms developed after 24 h. Both deficient and nondeficient groups had similar demographic data and bone density scores. The deficient group had significantly higher PTH (190 vs. 121 pg/ml, p = 0.015). Although IOPTH in the deficient group were higher at induction and 0 min after excision, the percentage drop from induction to 10 min after excision was similar. Ca was similar at 6 and 16 h in the two groups but was significantly lower in the deficient group at 24 h (2.10 vs. 2.45 mmol/l, p = 0.033). At 1 week, the proportion of LOH was significantly higher in the deficient group (12/42 vs. 3/34, p = 0.043) and in those with preoperative PTH > 100 pg/ml (15/57 vs. 0/19, p = 0.013). Vitamin D-3 deficiency was associated with a higher preoperative PTH level and a greater risk of LOH after MIP. However, the likely cause of LOH remains unclear as both low preoperative vitamin D-3 and high PTH levels could be responsible.