Body mass index and post-thyroidectomy hypocalcemia: a protective effect of overweight through non-surgical mechanisms—a propensity score-matched study

Postoperative hypocalcemia is a common complication after total thyroidectomy (TT). Recent studies suggest that body mass index (BMI) may influence its occurrence. This study aimed to investigate whether overweight reduces postoperative hypocalcemia after TT and to investigate the impact of surgical and non-surgical factors on postoperative hypocalcemia in patients undergoing total thyroidectomy. A retrospective analysis was conducted on 228 patients who underwent TT for papillary thyroid carcinoma between January 2021 and January 2024. Patients were categorized into overweight (BMI ≥ 25 kg/m2, n = 96) and non-overweight groups (BMI < 25 kg/m2, n = 132). Propensity score matching (PSM) was performed to balance confounding factors. Postoperative hypocalcemia, hypoparathyroidism rates, and related biochemical markers were compared between matched groups. After PSM (51 pairs), baseline characteristics were balanced except for Total Cholesterol (TC) (1.40 ± 0.83 vs 1.99 ± 1.80 mmol/L, P = 0.036), High-density lipoprotein cholesterol (HDL-C) (1.30 ± 0.34 vs 1.10 ± 0.23 mmol/L, P < 0.001), and fatty liver presence (35.5% vs 75.0%, P = 0.001). Postoperative hypocalcemia was significantly higher in the non-overweight group (78.4% vs 54.9%, P = 0.020), while hypoparathyroidism rates showed no significant difference (54.9% vs 62.7%, P = 0.546). Postoperative calcium levels were higher in the overweight group (2.11 ± 0.12 vs 2.05 ± 0.12 mmol/L, P = 0.014). Non-overweight patients are more likely to develop hypocalcemia after TT compared to overweight patients. The protective effect of overweight appears to operate through non-surgical mechanisms, as evidenced by similar hypoparathyroidism rates between groups. Further research is needed to elucidate the specific mechanisms involved.