Outcome of hypothyroidism caused by Hashimoto's thyroiditis.

BACKGROUND: Hypothyroidism is a common condition that is frequently irreversible and requires lifelong thyroid replacement therapy.
OBJECTIVE: To assess the incidence and factors that can predict reversibility of hypothyroidism caused by Hashimoto's thyroiditis.
METHODS: We studied 79 patients in whom Hashimoto's thyroiditis was diagnosed according to suggestive cytologic features and/or the presence of thyroid antibodies (antimicrosomal antibody titer, > or = 1:1600; antiglobulin antibody titer, > or = 1:400). All patients were initially hypothyroid (serum total thyroxine level, 83.5 +/- 28.6 nmol/L [6 +/- 2 micrograms/dL]; thyrotropin level, 24.7 +/- 28.3 mU/L). Levothyroxine sodium was then administered for 1 year to normalize results of thyroid blood tests. Thereafter, the treatment was stopped for 3 weeks and serum thyrotropin and total thyroxine concentrations were determined.
RESULTS: After withdrawal of levothyroxine treatment, thyroid 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 treatment, the presence of the following in a patient--of a goiter that is 35 g or larger, thyrotropin levels greater than 10 mU/L, and an anamnestic familial incidence of thyroid disease--was clearly associated with an increased incidence of recovery of normal thyroid function (relative risk, 5.4; 95% confidence interval, 2.8 to 10.7; P < .0002).
CONCLUSIONS: Our results confirm that hypothyroidism caused by Hashimoto's thyroiditis is not always permanent. The presence of a larger goiter and high thyrotropin levels at the time of diagnosis, associated with a familial incidence of thyroid disease, may be related to an increased incidence of hypothyroidism remission.