Thyroid function and antimicrosomal antibody during the course of silent thyroiditis.

The thyroid function and antithyroidal antibody were studied in 17 patients with silent thyroiditis unrelated to pregnancy. The antimicrosomal hemagglutination antibody (MCHA) was negative in ten of them (group I) and was positive in seven (group II). At one month after the thyrotoxicosis, thyroid function became normal in both groups. At two months after the onset of thyrotoxicosis, in group I T4 (8.1 +/- 1.8 micrograms/dl, Mean +/- SD), T3 (113 +/- 25 ng/dl) and TSH were normal. At that time T4 (2.8 +/- 2.2 micrograms/dl) was significantly decreased (p less than 0.001) compared with those of group I and the levels of TSH were strikingly increased in 6 patients in group II. The level of T3 (96 +/- 29 ng/dl) in group II was not different from that of group I. Therefore MCHA was negative in patients who did not develop hypothyroidism and MCHA was positive in patients who developed hypothyroidism. The development of hypothyroidism two months after thyrotoxicosis and positive MCHA are correlated. The Tg was elevated in 7 out of 13 patients (54%) with negative antithyroglobulin hemagglutination antibody and in the remainder was normal during thyrotoxicosis. The discrepancy between the level of Tg and thyroid hormones was discussed.