Early postoperative calcium-phosphate patterns as a predictor of prolonged calcium supplementation after total thyroidectomy.

PURPOSE: Postoperative hypocalcemia is a common complication after total thyroidectomy. While parathyroid hormone (PTH) is widely used for early prediction, its utility is limited by variable availability and accuracy. We explored the clinical utility of early postoperative calcium (Ca)-phosphate (P) patterns in predicting prolonged calcium supplementation. METHODS: The primary outcome was the duration of calcium supplementation after surgery. Calcium supplementation was considered prolonged when continuation exceeded 90 days, reflecting persistent impairment of calcium homeostasis. Supplementation was discontinued when serum calcium levels were maintained at ≥ 8.5 mg/dL on sequential measurements without supplementation. Patients who were still receiving supplementation at the end of the observation period were included, with duration calculated to the date of last follow-up. All patients who initiated calcium supplementation had documented follow-up beyond 90 days or were still receiving supplementation at the time of analysis; therefore, the primary outcome was reliably ascertained in all cases. RESULTS: Prolonged supplementation rates differed across groups: 42.3% in the low Ca-high P group, 30.0% in the intermediate group, and 7.1% in the high Ca-low P group. Duration also differed significantly (median: 52 vs. 24 vs. 2 days; p = 0.003). Multivariate analysis (n = 53 complete cases) revealed that the low Ca-high P pattern (odds ratio [OR] 4.22, 95% confidence interval [CI] 1.10-16.16; p = 0.036) and lateral neck dissection (OR 4.21, 95% CI 1.02-17.45; p = 0.048) were independently associated with prolonged supplementation. CONCLUSIONS: Early postoperative Ca-P patterns and lateral neck dissection may serve as practical indicators for predicting the risk of prolonged calcium supplementation after total thyroidectomy.