Spontaneous Recovery from Hypothyroidism in Autommune Thyroiditis / 대한내분비학회지

ABSTRACT

Background: A lifelong thyroxine therapy is indicated in all patients who have hypothyroidism as a result of autoimmune thyroiditis. However, it has been reported that some hypothyroid patients with autoimmune thyroiditis have spontaneous remission with restriction of iodine intake instead of thyroxine therapy. The purpose of study was to investigate how many hypothyroid patients with autoimmune thyroiditis can recover from hypothyroidism with restriction of iodine intake instead of thyroxine therapy and which factors predict recovery from hypothyroidism. Methods: We studied 64 patients with autoimmune thyroiditis(goitrous autoimmune thyroiditis 56, atrophic autoimmune thyroiditis 8). Thyroxine therapy was discontinued in patients with goitrous autoimmune thyroiditis on the way(group 1, n=32) or from the beginning(group 2, n=24) and atrophic autoimmune thyroiditis on the way(group 3, n-8). All patients were asked to avoid iodine-rich foods and thyroid function was monitored every one to two months for up to 35 months. Serum T3, T4, TSH concentrations, antithyroglobulin and antimicrosomal antibodies were measured by radioimmunoassay(RIA). TSH binding inhibitor immunoglobulin(TBII) was measured in serum using radioreceptor assay. Two hundred micrograms of thyrotropin releasing hormone (TRH) were given as intravenous bolus and TSH levels were measured in blood samples taken at 0, 30, and 60 minutes. All values were expressed as mean+-SEM. Statistical analysis was done with paired or non-paired t-test, ANOVA, and the Chi-square test. Statistical significance was defined as p-value below 0.05. Results: Thirteen(40.6%) of 32 patients in group 1 remained euthyroid after 12-35 months of discontinuation of thyroxine therapy. The other 19(59.4%) patients in group 1 had recurrences of hypothyroidism within 3 months after discontinuation of thyroxine therapy. In 11(45.8%) out of 24 patients in group 2, serum TSH concentrations declined below 5 mU/L within 3 months without thyroxine therapy. The other 13(54.2%) patients in group 2 remained hypothyroid till 2-16 months and the thyroxine was given. In contrast, all 8 patients in group 3 had recurrences of hypothy- roidism within 3 months after stopping thyroxine therapy. When we compared the recovered patients of goitrous autoimmune thyroiditis with the non-recovered patients of goitrous autoimmune thyroiditis, regardless of thyroxine therapy from the beginning, age at onset of disease of the 24 recovered patients was significantly younger than the 32 non-recovered patients(30.1+2.0 years vs. 40.2+ 2.4 years; p=0.004). Concl#usion These findings suggest that 42.9% of hypothyroid patients with goitrous autoim- mune thyroiditis remain or become spontaneously euthyroid with restriction of iodine intake instead of thyroxine therapy. Young age may be a predicting factor of recovery from hypothyroidism in goitrous autoimmune thyroiditis.