Thyroid vein thrombosis in a young woman with methylenetetrahydrofolate reductase gene mutation receiving cyproterone acetate/ethinylestradiol treatment for polycystic ovary syndrome: a case report.

Thyroid vein thrombosis is a rare variety of venous thrombosis. The use of oral contraceptives and heterozygous methylenetetrahydrofolate reductase (MTHFR) gene mutation could have synergistic effects on the onset of venous thromboembolism. We report a 28-year-old woman with thyroid vein thrombosis. The thrombosis was possibly provoked by a combination of heterozygous MTHFR gene mutation and the use of a combined oral contraceptive (COC) containing cyproterone acetate/ethinylestradiol (CPA/EE) for polycystic ovary syndrome (PCOS). The patient was treated successfully with low molecular weight heparin and oral anticoagulation. The thyroid vein thrombosis resolved and the patient was advised to maintain lifelong use of anticoagulation therapy. Our report emphasizes that the combination of heterozygous MTHFR gene mutation, PCOS, and the use of a COC-containing CPA/EE could increase risk of thyroid vein thrombosis in young adults.