A 59-year-old woman after total strumectomy due to papillary thyroid carcinoma (pT1a,N0,M0) was admitted to the Department of Endocrinology to provide an ablative dose of radioactive iodine. Despite the 4-week thyroxine withdrawal, serum TSH was 7.24 microU/ml (normal 0.27-4.2 microU/ml) with normal concentrations of free hormones (fT3 4.98 pmol/l, fT4 12.09 pmol/l). In ultrasonography of the neck thyroid tissue in the thyroid bed with dimensions 11 x 13 x 20 mm was detected. Serum concentration of thyroglobulin was 102.7 ng/ml, autoantibodies against Tg (anti-Tg) 30 U/ml. In the study of whole-body scintigraphy with 131-I, out of focus tracer accumulation in the thyroid bed, there were no further outbreaks of tracer uptake. In the imaging studies of the neck and chest metastases were not found. Gynecological ultrasound revealed the presence of bilateral ovarian tumors with dimensions 6 x 4 cm in the right ovary, 7 x 3 cm in the left one. Due to the lack of TSH stimulation radioiodine treatment was abandoned. The patient underwent gynecological surgery - total hysterectomy with appendages was performed. Histopathological diagnosis was bilateral ovarian teratomas with the presence of thyroid tissue. The patient was re-admitted to the Department of Endocrinology for subsequent radioactive iodine therapy. After 4-week levothyroxine withdrawal the following results were obtained: TSH 36.34 microU/ml, Tg 16.85 ng/ml, aTg 24 U/ml. The patient received 150 mCi of 131-I, then suppressive doses of thyroxine. Diagnosis after a control period of 12 months is currently planned.