Endocrine Abstracts

Introduction: Struma ovarii (SO) is a rare ovarian teratoma composed predominantly (more than 50%) or entirely of thyroid tissue. It constitutes 2% to 4% of ovarian teratomas. This tumor is often asymptomatic and discovered incidentally. Only 8% of patients present clinical hyperthyroidism.

Case report: A 42-year-old woman presented palpitations, anxiety, sweating, emotional lability and weight loss for several months. Physical examination revealed goitre, tachycardia and slight tremor. Laboratory tests confirmed hyperthyroidism: thyrotropin (TSH) 0.01 mcU/ml (0.3–5), serum-free thyroxine 5.21 ng/dL (FT4) (0.9–2.1), serum-free triiodothyronine (FT3) 22.5 pg/ml (2.57–4.43) and thyrotropin receptor antibody (TRAb) 21.78 U/l (positive >2). Thyroid ultrasound identified a multinodular goitre with a dominant nodule of 14 mm in left lobe. Technetium thyroid scan showed diffuse uptake. She was diagnosed as having Graves’ disease (GD) and started on thiamazole and propranolol. Several months later, she remained hyperthyroid and appeared proptosis, lid retraction and ocular chemosis. Magnetic resonance of the orbits demonstrated bilateral mild swelling of extraocular muscles. She was diagnosed with Graves’ ophthalmopathy too. After that, it was decided thyroidectomy. In addition, oligoamenorrhea appeared and ultrasound and magnetic resonance of the abdomen and pelvis detected an 11×11×9 cm solid-cystic mass in right ovarian. The patient underwent right salpingo-oophorectomy. Histology revealed a benign SO. Immediately, ocular disease and hyperthyroidism improved. Subsequently, total thyroidectomy was performed, which showed GD and benign thyroid nodules.

Conclusions: The diagnosis of functioning SO in presence of GD may be a challenge and it may be difficult to determine the precise cause of hyperthyroidism. When a patient has increased thyroid uptake of technetium in the scan, an ectopic hormone production is not suspected. When SO is surgically removed and subsequently the hyperthyroidism and ocular disease improve considerably, the diagnosis of functioning SO is quite likely.