The characteristics of hypoparathyroidism in patients with Hashimoto thyroiditis (HT) after total thyroidectomy are not well established. The aim of this study was to investigate the relationship between hypoparathyroidism and loss of parathyroid glands in patients with or without HT who underwent total thyroidectomy.

Patients who underwent total thyroidectomy were divided into two groups; with HT (n=166) and without HT (n=526). Clinicopathologic characteristics were compared between the two groups.

The mean numbers of parathyroid glands in specimens were significantly smaller in the with HT group than in the without HT group (0.34±0.51 vs. 0.42±0.58, P=0.003). The rate of transient hypoparathyroidism was significantly higher in the with HT group than in the without HT group (51.8% vs. 34.6%, P=0.000). Serum total calcium levels in patients who experienced transient hypoparathyroidism did not differ significantly between groups (P=0.335). The incidence of transient hypoparathyroidism of patients who preserved all four parathyroid glands or sacrificed one parathyroid gland was higher in the with HT group than in the without HT group, although that of patients who sacrificed two or more parathyroid glands was similar between groups. The incidence of permanent hypoparathyroidism in the two groups did not differ (P=0.546).

Patients with HT had a higher rate of transient hypoparathyroidism after total thyroidectomy, particularly patients who preserved all four or three parathyroid glands. It is likely that the blood supply to the parathyroid gland might be vulnerable in patients with HT. Therefore, even though all parathyroid glands were preserved, careful monitoring of hypoparathyroidism is necessary after total thyroidectomy in patients with HT.