Risk factors for medically treated hypocalcemia after surgery for Graves' disease: a Swedish multicenter study of 1,157 patients.

BACKGROUND

For reasons that remain unclear, surgery for Graves' disease is associated with a higher risk of hypocalcemia than surgery for benign atoxic goiter. In the present study, we evaluated risk factors for postoperative hypocalcemia in patients undergoing operation for Graves' disease.

METHODS

Data from 1,157 patients who underwent operation for Graves' disease between 2004 and 2008 were extracted from the Scandinavian database for Thyroid and Parathyroid Surgery. Risk factors for postoperative hypocalcemia (in-hospital i. v. calcium; treatment with vitamin D analog at discharge, at 6 weeks, and at 6 months postoperatively) were evaluated by logistic regression analysis.

RESULTS

Risk factors for i. v. calcium were low hospital volume of thyroid surgery (odds ratio [OR]: 95 % confidence interval [95 % CI], 0.99: 0.99-1.00), age (0.95: 0.91-1.00), operative time (1.02: 1.01-1.02), university hospital (12.91: 2.68-62.30), and reoperation for bleeding (10.32: 1.51-70.69). The risk for treatment with vitamin D at discharge increased with operative time (1.01: 1.00-1.02), excised gland weight (1.01: 1.00-1.01), parathyroid autotransplantation (5.19: 2.28-11.84), and reoperation for bleeding (12.00: 2.43-59.28). At 6 weeks, vitamin D medication was associated with gland weight (1.00: 1.00-1.01), and preoperative medication with β-blockers (4.20: 1.67-10.55). At 6 months, vitamin D medication was associated with gland weight (1.00: 1.00-1.01) and reoperation for bleeding (10.59: 1.58-71.22).

CONCLUSIONS

Risk factors for medically treated hypocalcemia varied at different times of follow-up. Young age, operative time, type of hospital, and parathyroid autotransplantation were associated with early postoperatively hypocalcemia. Preoperative β-blocker treatment was a risk factor at the first follow-up. At early and late follow-up, gland weight and reoperation for bleeding were associated with medically treated hypocalcemia.