Struma ovarii is a teratoma of the ovaries that contains a large amount of
thyroid tissue. Like the cervical thyroid gland, this ectopic thyroid tissu
e can become autonomous. We present a case of hyperthyroidism caused by thy
roid tissue in a large ovarian cystic teratoma and provide detailed endocri
nological, radiological, and pathological preoperative and postoperative da
ta. This is also the first documented case of struma ovarii in association
with a secreting pituitary tumor. In addition, we provide a retrospective p
athological analysis of 1390 surgically removed ovarian tumors at 2 major a
cademic centers.