Transient hypothyroidism in a case of untreated Graves' disease.

We report the case of a 41-year-old female with untreated Graves' disease who developed transient hypothyroidism. The hypothyroid state was thought to be caused by silent thyroiditis, based on findings of a non-tender thyroid gland, suppressed thyroidal radioactive iodine uptake, normal white blood cell count and normal erythrocyte sedimentation rate, and ultrasonogram results. Silent thyroiditis may play a role in the development of Graves' hyperthyroidism. Results for TSH-binding inhibitor immunoglobulins (TBII), thyroid-stimulating antibodies (TSAb), anti-thyroglobulin antibodies (TgAb) and anti-thyroid peroxidase antibodies (TPOAb) were positive before the development of hypothyroidism. Their levels were decreased during and after the hypothyroid phase. These results suggest that the same or similar mechanism(s) were involved in the production of these different antibodies during the course of her illness.