Abstract. Only 150 cases of struma ovarii (i.e., goiter of the ovary) have been reported in the medical literature. The condition is characterized by the presence of thyroid tissue in an ovarian tumor, typically as a part of a teratoma. We report the first case of Hashimoto’s thyroiditis concurrent with struma ovarii, a thyroid gland with Hürthle cells, and positive antithyroid antibodies despite reference range thyroid function test results.

Case Report. A young woman presented to the office with pelvic pain. Ultrasound revealed a complex right ovarian mass. The mass was surgically removed, and biopsy revealed struma ovarii with Hashimoto’s thyroiditis. After surgery, the patient’s thyroid stimulating hormone level decreased into to within the reference range. Her free T4 and free T3 are within their reference ranges, although her thyroid peroxidase and antithyroglobulin levels are elevated. She continues to remain asymptomatic with reference range thyroid function test results. We recommend that physicians maintain a high index of suspicion this struma ovarii in young patients who present with an ovarian mass, as resolution of thyroid function abnormalities can be achieved by surgical removal of the ovarian mass.