Endocrine Abstracts

Introduction: Struma ovarii is often initially diagnosed as a suspected ovarian malignancy due to atypical characteristics on the imaging and hyperthyroidism is only seen in about 8% of presentation making thyroid function test (TFT) an unreliable test to suspect it pre-operatively. There are few case reports on its varied structural and functional characteristics in the literature. However, there are no reports of the influence of an intrinsic thyroid disease on its functional characteristics.

Case report: A 40-year-old lady with dual presentation of struma ovarii and autoimmune thyroiditis with presentation of overt hypothyroidism after salpingo-oophorectomy for a suspected ovarian malignancy. She initially presented to Gynaecologist with intermittent post-coital right sided sharp abdominal pain, bloating and no weight changes. The point of care pelvic ultrasound confirmed an enlarged irregular highly vascularised multilocular solid-cystic lesion in right ovary suspicious of a malignancy. The initial blood tests include tumour makers CA125 39 kIU/l (0-35), CEA 1.1 (0-3.4) mg/l, CA19 2 kIU/l (0-27), AFP 2.2 kIU/l (0-6) and TSH of 3.79. Other routine biochemistry within normal limits. She underwent salpingo-oophrectomy and the histology confirmed struma ovarii with atypia. No pathogenic mutations were identified and RNA based NGS testing showed no NTRK fusions. Following the result of histology, patient was referred to Endocrinology clinic with unintentional weight gain of 4 kg within two months and repeat TFT showed TSH of >100 and FT4 2.2. Further investigations include TPO of 1300 IU/ml (0-60) and thyroid USS suggestive of autoimmune thyroiditis (Hashimoto’s). She was commenced on Levothyroxine which improved her symptoms.

Conclusion: This case illustrates the uncertainty in TFT pictures that could be associated with struma ovarii in the presence of intrinsic thyroid disease and this could further complicate the ongoing constraints of pre-operative suspicion of struma ovarii before histology diagnosis. To our knowledge, this is the first report of such association.