A 31-year-old woman presents with palpitations, weight loss, tremor, and a neck that is clinically normal. Thyroid function tests show suppressed TSH with elevated free T4. Pelvic ultrasound reveals a 7 cm right adnexal mass with solid and cystic areas. Which ovarian tumour is the most likely cause of her thyrotoxicosis?

• A Granulosa cell tumour
• B Sertoli-Leydig cell tumour
• C Serous cystadenofibroma
• D Struma ovarii ✓

Explanation

Struma ovarii is a monodermal mature teratoma composed predominantly of thyroid tissue, and functional thyroid tissue within the ovary can secrete sufficient hormone to cause thyrotoxicosis while the neck remains normal on examination. Granulosa and Sertoli-Leydig tumours produce oestrogen and androgen respectively, not thyroid hormone. Serous cystadenofibromas are non-functional epithelial tumours. Recognition matters because the correct treatment is oophorectomy, after which the biochemical hyperthyroidism resolves.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.