A 31-year-old woman has tremor, weight loss and heat intolerance for 3 months. Pulse is 104/min, TSH is suppressed at 0.01 mIU/L and free T4 is raised. There is no goitre, no exophthalmos, and thyroid autoantibodies are negative. Ultrasound shows a 7 cm left adnexal mass with echogenic foci. What is the most likely diagnosis?
- A Ovarian carcinoid
- B Struma ovarii ✓
- C Graves disease with coincidental dermoid cyst
- D Leydig cell tumour
Correct answer: B. Struma ovarii
Explanation
Struma ovarii is a monodermal mature teratoma composed predominantly of thyroid tissue and is the commonest cause of ovarian thyrotoxicosis. The absence of goitre and orbitopathy with negative antibodies argues against Graves disease, making option C untenable despite the dermoid-like ultrasound appearance. Ovarian carcinoid produces serotonin-related symptoms such as flushing and diarrhoea, not thyrotoxicosis. Management includes surgical removal, with radioiodine reserved for persistent hyperthyroidism or malignant struma.
Reference: Novak's Gynecology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.