Transient hypothyroidism associated with increased anti-microsomal antibodies.

An unusual case of transient hypothyroidism during the course of chronic thyroiditis was reported. A 25 years old female noticed the remarkable enlargement of thyroid gland 3 months after paturition and was developed to be hypothyroidism with decreased blood thyroid hormone and increased serum TSH. The patient recovered to be euthyroid spontaneously in association with the decrement of goiter size. Anti-thyroid microsomal antibody increased concomitantly with hypothyroid period and decreased parallel with the recovery of thyroid function. The ratio of TSH potency estimated by bioassay to that by immunoassay changed during the course. Possible etiologic factors of this transient changes were discussed.