OUTCOME OF HYPOTHYROIDISM CAUSED BY HASHIMOTOS-THYROIDITIS

Background: Hypothyroidism is a common condition that is frequently ir reversible and requires lifelong thyroid replacement therapy. Objectiv e: To assess the incidence and factors that can predict reversibility of hypothyroidism caused by Hashimoto's thyroiditis. Methods: We studi ed 79 patients in whom Hashimoto's thyroiditis was diagnosed according to suggestive cytologic features and/or the presence of thyroid antib odies (antimicrosomal antibody titer, greater than or equal to 1:1600; antiglobulin antibody titer, greater than or equal to 1:400). All pat ients were initially hypothyroid (serum total thyroxine level, 83.5+/- 28.6 nmol/L [6+/-2 mu g/dL]; thyrotropin level, 24.7+/-28.3 mU/L). Lev othyroxine sodium was then administered for 1 year to normalize result s of thyroid blood tests. Thereafter, the treatment was stopped for 3 weeks and serum thyrotropin and total thyroxine concentrations were de termined. Results: After withdrawal of levothyroxine treatment, thyroi d blood tests showed that the degree of hypothyroidism worsened in 20 patients, remained unchanged in 40, and improved in 19. Nine patients (11.4%) did show normalization of the thyroid blood tests. Before trea tment, the presence of the following in a patient-of a goiter that is 35g or larger, thyrotropin levels greater than 10 mU/L, and an anamnes tic familial incidence of thyroid disease-was clearly associated with an increased incidence of recovery of normal thyroid function (relativ e risk, 5.4; 95% confidence interval, 2.8 to 10.7; P<.0002). Conclusio ns: Our results confirm that hypothyroidism caused by Hashimoto's thyr oiditis is not always permanent. The presence of a larger goiter and h igh thyrotropin levels at the time of diagnosis, associated with a fam ilial incidence of thyroid disease, may be related to an increased inc idence of hypothyroidism remission.