Postoperative hypocalcemia after thyroidectomy for Graves' disease

Background: It is believed that patients who undergo thyroidectomy for Graves' disease are more likely to experience postoperative hypocalcemia than patients undergoing total thyroidectomy for other indications. However, no study has directly compared these two groups of patients. The aim of this study was to determine whether there was an increased incidence or severity of postoperative hypocalcemia in patients who underwent thyroidectomy for Graves' disease. Methods: An institutional review board-approved database was created of all patients who underwent thyroidectomy from 1998 to 2009 at the Johns Hopkins Hospital. There were a total of 68 patients with Graves' disease who underwent surgery. Fifty-five patients who underwent total thyroidectomy were randomly selected and served as control subjects. An analysis was conducted that examined potential covariates for postoperative hypocalcemia, including age, gender, ethnicity, preoperative alkaline phosphatase level, size of goiter, whether parathyroid tissue or glands were present in the specimen, and the reason the patient underwent surgery. Specific outcomes examined were calcium levels on postoperative day 1, whether or not patients experienced symptoms of hypocalcemia, whether or not Rocaltrol was required, the number of calcium tablets prescribed upon discharge, whether or not postoperative tetany occurred, and calcium levels 1 month after discharge. Results: Each outcome was analyzed using a logistic regression. Graves' disease patients had a significantly (p-value<0.001) higher odds of greater number of calcium tablets prescribed upon discharge. Further, 6 of 68 patients with Graves' disease and no patient in the control group were readmitted with tetany (p=0.033). There was a trend, though not significant, toward patients with Graves' disease having a higher prevalence of hypocalcemia the day after thyroidectomy and 1 month later. Conclusions: Patients with Graves' disease are more likely to require increased dosages of calcium as well as experience tetany postoperatively than patients undergoing total thyroidectomy for other indications. This suggests that patients operated upon for Graves' disease warrant close followup as both inpatients and outpatients for signs and symptoms of hypocalcemia.