Association of Hypocalcemia and Magnesium Disorders With Thyroidectomy in Commercially Insured Patients.

Importance: Hypocalcemia is a common complication of total thyroidectomy. Objectives: To identify factors associated with hypocalcemia after total thyroidectomy and to explore the association between hypocalcemia, magnesium disorders, and costs of care. Design, Setting, and Participants: A retrospective cross-sectional analysis was performed using data from the MarketScan Commercial Claim and Encounters database on 126 766 commercially insured patients younger than 65 years undergoing total thyroidectomy between January 1, 2010, and December 31, 2012. Statistical analysis was performed from January 1, 2016, to May 30, 2019. Main Outcomes and Measures: Short- and long-term hypocalcemia and the costs of care were examined using multivariable regression modeling. Results: Among the 126 766 patients in the study (81.6% women; mean age, 46.5 years [range, 18-64 years]), postoperative hypocalcemia was present in 19.1% of patients in the initial 30-day postoperative period and in 4.4% of patients at 1 year. Magnesium disorders were present in 2.1% of patients at the time of surgery. Short- and long-term hypocalcemia were significantly more likely in women (short-term: odds ratio [OR], 1.39 [95% CI, 1.29-1.50]; long-term: OR, 1.69 [95% CI, 1.52-1.89]), those younger than 40 years (short-term: OR for ages 40-64 years, 0.83 [95% CI, 0.78-0.87]; long-term: OR for ages 40-64 years, 0.73 [95% CI, 0.67-0.79]), those with a diagnosis of thyroiditis (short-term: OR, 1.48 [95% CI, 1.16-1.89]; long-term: OR, 1.60 [95% CI, 1.13-2.26]) or cancer (short-term: OR, 1.32 [95% CI, 1.05-1.67]; long-term: OR, 1.17 [95% CI, 0.83-1.63]), vitamin D deficiency (short-term: OR, 1.96 [95% CI, 1.74-2.21]; long-term: OR, 3.72 [95% CI, 3.30-4.18]), concurrent lateral neck dissection (short-term: OR, 1.51 [95% CI, 1.37-1.66]; long-term: OR, 1.95 [95% CI, 1.69-2.26]), concurrent central neck dissection (short-term: OR, 1.15 [95% CI, 1.07-1.24]; long-term: OR, 1.25 [95% CI, 1.12-1.40]), intraoperative parathyroid (short-term: OR, 1.58 [95% CI, 1.46-1.71]; and long-term: OR, 2.05 [95% CI, 1.82-2.31]) or recurrent laryngeal nerve injury (short-term: OR, 1.49 [95% CI, 1.27-1.74]; long-term: OR, 2.04 [95% CI, 1.64-2.54]), and magnesium disorders (short-term: OR, 8.40 [95% CI, 7.21-9.79]; long-term: OR, 25.23 [95% CI, 19.80-32.17]). Compared with the initial postoperative period, the odds of hypocalcemia decreased by 90.0% (OR, 0.10 [95% CI, 0.09-0.11]) at 6 months and 93.0% (OR, 0.07 [95% CI, 0.06-0.08]) at 1 year. After controlling for all other variables, magnesium disorders were associated with the highest odds of short- and long-term postoperative hypocalcemia. Hypocalcemia ($3392) and magnesium disorders ($14 314) were associated with increased mean incremental 1-year costs of care. Conclusions and Relevance: Hypocalcemia is common after total thyroidectomy but resolves in most patients by 1 year. Magnesium disorders are significantly independently associated with short- and long-term hypocalcemia and are associated with greater costs of care. These data suggest a potentially modifiable target to reduce the incidence and cost of long-term hypocalcemia at patient and systemic levels.