An Unusual Case of Graves’ Disease Coexisting with Struma Ovarii Iqra Javeed MD1, Amin Sabet MD2, and Jacqueline Kung MD1 1Division of Endocrinology, Diabetes, and Metabolism, Tufts Medical Center, Boston, MA; 2Signature Healthcare, Brockton, MA Introduction Case Presentation Table 1: Thyroid Function Tests since Diagnosis Struma ovarii is a rare tumor consisting primarily of thyroid components occurring in a teratoma or dermoid in the ovary. Only one other case of struma ovarii presenting as a pseudo-Meigs’ syndrome coexisting with Graves’ disease has been described in the literature. 54 year old Caucasian woman who presented to her PCP with fatigue and weight loss of 40 lbs. in the last 1.5 years. Her history was also significant for tremors, increased irritability, and prominent, bulging eyes. Physical exam was significant for a non-palpable thyroid, bitemporal wasting, proptosis of 22 mm in the right eye, 18 mm in the left eye, right eyelid retraction, periorbital edema, and lid lag (figure 1). Labs at diagnosis showed TSH <0.005, FT4 4.32 ng/dl (nl 0.70-1.48), TT3 530 ng/dl (nl 58-159). Thyroid stimulating immunoglobulin was elevated at 441% baseline (normal <140). Based on her exam and laboratory results, she was diagnosed with Graves’ disease and started on methimazole 20mg daily. Three weeks later, she presented to the hospital with severe bloating and was found to have a 10cm pelvic mass along with ascites and a right pleural effusion (figure 2). TFTs now showed a suppressed TSH with normal FT4 and TT3. Her methimazole dose was decreased, and she underwent ovarian surgery. Pathology of the ovarian mass showed a 13.5cm ovarian teratoma predominantly composed of mature thyroid tissue (struma ovarii) notable for hyperplastic changes suggestive of Graves' disease without any evidence of malignancy. On post-op day 2, TFTs were checked which showed TSH <0.005, FT4 0.81mg/dl and TT3 <25 ng/dl, and methimazole was discontinued. On post-op day 5, hypothyroidism worsened with FT4 0.46 ng/dl and TT3 <25ng/dl, and levothyroxine 25mcg daily was initiated. The thyroid was visible on imaging and within normal limits in size. A month after her surgery, the patient developed recurrent hyperthyroidism (T3-predominant); therefore, levothyroxine was stopped and methimazole restarted. Time TSH (nl 0.35-4.94 uIU/ml) FT4 (nl 0.70-1.48 ng/dl) TT3 (nl 58-159 ng/dl) Treatment At diagnosis <0.005 4.32 530 Started on methimazole 20mg daily 9 days after diagnosis 3.32 351 On methimazole 20mg daily 21 days after diagnosis <0.03 1.22 121 Methimazole decreased to 10mg daily 25 days after diagnosis (post-operative day 0) 0.84 50 Underwent resection of ovarian mass 27 days after diagnosis (post-operative day 2) 0.81 <25 Methimazole stopped 31 days after diagnosis (post-operative day 4) 0.52 No treatment 32 days after diagnosis (post-operative day 5) 0.46 Started on levothyroxine 25mcg daily 41 days after diagnosis (post-operative day 14) 0.89 105 On levothyroxine 25mcg daily 58 days after diagnosis (post-operative day 31) 1.55 199 Levothyroxine stopped and started on methimazole 10mg daily 76 days after diagnosis (post-operative day 49) 1.08 140 Methimazole 10mg daily Hospital Course Figure 1: Graves’ Opthalmopathy Conclusion The diagnosis of struma ovarii should be considered in patients who present with thyrotoxicosis and a pelvic mass. TFTs need to be monitored carefully pre- and post-operatively in these patients. Post-operative Course Discussion This is the only case reported in the literature where a patient with Graves’ disease transiently became hypothyroid due to resection of a functional struma ovarii. Wolff-Chaikoff effect may have been contributory as she had undergone multiple CT imaging studies with intravenous contrast for staging of the ovarian mass. Figure 2: CT Abdomen/Pelvis showing 10cm Ovarian Mass