A case of low thyroid radioactive iodine uptake (RAIU) thyrotoxicosis due t
o a large struma ovarii comprising pure thyroid tissue is presented, includ
ing a detailed diagnostic evaluation, histopathology, and demonstration of
rapid recovery of native thyroid function after surgical excision. In addit
ion, the first comprehensive analysis of thyroglobulin obtained from an ova
rian struma is reported.