Co-Existing Graves Disease with Benign Struma Ovarii: A Case Report

ABSTRACT Objective: We describe a case of co-existing Graves disease and struma ovarii, which has seldom been reported. Methods: We present the clinical, biochemical, and imaging findings of one such case and review the relevant literature for the evaluation and treatment of co-existing Graves disease and struma ovarii. Results: A 33-year-old woman presented with a palpable right-sided pelvic mass, clinical and biochemical thyrotoxicosis, and elevated thyroid-stimulating hormone receptor antibody levels. On ultrasound, the thyroid was enlarged and hyperemic with a heterogeneous echotexture. Pelvic ultrasound showed a complex cystic-solid right adnexal lesion with calcifications (14 × 5.4 × 8.3 cm), favored to be an ovarian teratoma. Magnetic resonance imaging (MRI) of the pelvis showed bilateral adnexal lesions of mixed T1 and T2 signal intensity containing fat, soft tissue components, and calcification suspicious for teratomas. Whole-body uptake and scan showed homogenous thyroid uptake at 2 hours and 24 hours of 54% and 77%, respectively, and increased activity in the right adnexa. Following bilateral laparoscopic ovarian cystectomies, postoperative histology showed benign, bilateral cystic teratomas with histologic evidence of hyperfunctioning thyroid tissue bilaterally. Positive immunohistochemical staining of the teratomas for thyroid transcription factor 1 confirmed the presence of thyroid tissue. Postoperative whole-body scintigraphy did not show residual pelvic iodine uptake. Conclusion: Our patient had clinical, biochemical, and radiographic evidence of Graves disease with thyrotoxicosis while also having bilateral ovarian teratomas containing hyperfunctioning thyroid tissue. Although bilateral, the right-sided teratoma was likely the primary pelvic source of thyroid hormone secretion given that increased iodine uptake on whole-body scan was seen only in the right adnexa. In cases of co-existing Graves disease and struma ovarii, pre-operative MRI and whole-body scintigraphy with 123I is preferred for diagnosis. Keys to management include ensuring patients are euthyroid prior to surgery to avoid precipitating a thyroid storm, titrating antithyroid medications closely postoperatively, and completing repeat whole-body scintigraphy postoperatively to assess for residual thyroid tissue in the pelvis. Abbreviations: CT = computed tomography; SO = struma ovarii; SPECT = single-photon emission computed tomography; TSH = thyroid-stimulating hormone; TTF-1 = thyroid transcription factor 1