Silent Disruptions: Predicting Post-Thyroidectomy Hypocalcemia Through Early Postoperative Electrolyte Patterns

Mia Hoffmann¹, Felix Wagner², James Whitaker³

Abstract

Background: Hypocalcemia remains the most common complication after total thyroidectomy, with incidence ranging from 15% to 35%. Timely prediction may reduce morbidity and hospital stay.

Objective: To determine whether early postoperative calcium-phosphate dynamics can reliably predict hypocalcemia within 48 hours of surgery.

Methods: A prospective cohort of 482 thyroidectomy patients was evaluated between 2021 and 2024. Serum calcium, phosphate, magnesium, and parathyroid hormone (PTH) levels were measured preoperatively and at 6, 12, and 24 hours postoperatively. Symptomatic hypocalcemia was defined by standard clinical criteria.

Results: Postoperative hypocalcemia occurred in 28.4% of patients. A 24-hour calcium drop ≥ 0.9 mg/dL predicted hypocalcemia with sensitivity 84% and specificity 78% (AUC 0.89). PTH <15 pg/mL at 6 hours had sensitivity 81% and specificity 73%. Combining calcium and PTH improved AUC to 0.93. Serum phosphate elevation (>4.8 mg/dL) at 12 hours was independently associated with hypocalcemia (OR 2.4, 95% CI 1.6–3.9). Early replacement therapy reduced symptom duration by 38%.

Conclusion: Early postoperative calcium-phosphate fluctuations provide a reliable, rapid method for predicting hypocalcemia after thyroidectomy. Combining calcium drop and PTH enhances predictive accuracy and supports individualized supplementation strategies.