Resolution of hyperthyroidism and thyroid antibodies following struma ovarii resection: an uncommon entity.

We report a case of 34-year-old clinically asymptomatic woman who had been followed for 6 years for hyperthyroidism with thyroid stimulating hormone <0.006 uIU/mL, free T4 1.98 ng/mL, free T3 5.3 pg/mL, elevated thyroid stimulating immunoglobulin 1.70 IU/L, thyroid peroxidase antibody 38 IU/mL and thyroglobulin antibody 9.3 IU/mL. Radioiodine thyroid scan showed minimal uptake in both thyroid lobes (24-hour uptake was 0.3%). She subsequently underwent evaluation for lower abdominal pain and menstrual irregularities, which revealed a large left ovarian cyst measuring 15.9 cm × 10.8 cm × 13.2 cm and right-sided ovarian cyst measuring 2.7 cm × 3.3 cm × 3.5 cm. Laparoscopic bilateral ovarian cystectomy was performed and the final pathology revealed struma ovarii of the left ovarian cyst with the entire ovarian tumour made up of benign thyroid tissue. Thyroid function tests performed 3 months after surgical removal of struma ovarii showed euthyroidism. We present a rare case with detailed laboratory and immunological data before and after ovarian extirpation with resolution of hyperthyroidism associated with functional struma ovarii. © BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.