Impact of Obesity on Risk of Hypocalcemia After Total Thyroidectomy: Targeted National Surgical Quality Improvement Program Analysis of 16,277 Patients.

INTRODUCTION: Hypocalcemia following total thyroidectomy (TT) is common due to postoperative parathyroid dysfunction and vitamin D deficiency. Given the association between obesity and vitamin D deficiency, we sought to correlate body mass index (BMI) with hypocalcemia after TT. METHODS: Patients undergoing TT between 2016 and 2020 were identified from the American College of Surgeons National Surgical Quality Improvement Program thyroidectomy-targeted database. Univariable and multivariable regressions, stratified by BMI category (normal, overweight, obese), identified factors associated with hypocalcemia prior to discharge, within 30 d, and severe hypocalcemic events (emergent evaluation, intravenous calcium supplementation, or readmission). RESULTS: Sixteen thousand two hundred seventy seven TT were performed with available BMI data. Three thousand five hundred thirty one (21.7%) patients had normal BMI, 4823 (29.6%) were overweight, and 7772 (47.7%) were obese. Patients with BMI ≥ 25 had decreased risk of hypocalcemia before discharge (9.8% versus 13%, odds ratio [OR] 0.73, P < 0.001), 30 d (8.1% versus 10.4%, OR 0.76, P < 0.001), and severe hypocalcemic events (5.5% versus 6.4%, OR 0.84, P = 0.029) compared to normal BMI patients. On multivariable analysis for normal BMI patients, age < 45 y was a risk factor for hypocalcemia before discharge, 30 d, and severe hypocalcemic events (P < 0.05 for all). Additional risk factors in this group for 30-d hypocalcemia included parathyroid autotransplant and central neck dissection (P < 0.05) and recurrent laryngeal nerve injury for severe hypocalcemic events (P = 0.01). CONCLUSIONS: Younger patients with BMI < 25 are at an increased risk for hypocalcemia and severe hypocalcemic events after TT. These patients may benefit from preoperative counseling and increased calcium/vitamin D supplementation to reduce prolonged hospitalization and mitigate morbidity.