Hypothyroidism due to Hashimoto thyroiditis post struma ovarii excision

Struma ovarii is a rare ovarian teratoma that may produce hyperthyroidism. The association with Hashimoto thyroiditis HT, however is rare and has been reported in only one case. We report a case of HT following the resection of struma ovarii tumor, after which the patient became frankly, hypothyroid with elevated thyroid stimulating hormone and low thyroxin levels. Her thyroid peroxidase antibodies were positive. She improved after initiation of levothyroxine replacement therapy. We believe her euthyroid status preoperatively was due to thyroid hormone secretion by struma ovarii itself.