A 28-year-old woman has palpitations, weight loss, and tremor with a normal-sized thyroid gland and suppressed TSH. Pelvic ultrasound reveals a 7 cm right adnexal mass. After thyroidectomy is excluded by neck examination, radioiodine scan shows uptake confined to the pelvis. The most likely diagnosis is:

• A Dysgerminoma
• B Mature cystic teratoma with carcinoid
• C Struma ovarii ✓
• D Ovarian thecoma

Explanation

Struma ovarii is a monodermal teratoma composed predominantly of mature thyroid tissue and is the commonest cause of ovarian thyrotoxicosis. It accounts for a small fraction of mature cystic teratomas and causes clinical hyperthyroidism in roughly 5 to 8 percent of cases. Uptake on radioiodine scan localised to the pelvis with a normal neck confirms functioning ectopic thyroid tissue. Carcinoid within a teratoma causes flushing and diarrhoea, not thyrotoxicosis.

Reference: Williams Gynecology, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.