Endocrine Abstracts

Case presentation: A 40-year-old woman was admitted to the department of cardiology in our hospital due to iliofemoral deep vein thrombosis (DVT) in August 2010. It seemed that thrombosis was induced by the oral contraceptive (OC) which she had taken. Her serum level of von Willebrand factor was elevated. After the admission, the insertion of a temporary inferior venous cava (IVC) filter and thrombectomy were performed as well as starting of thrombolytic therapy and discontinuing of OC. She was referred to our department for the evaluation of thyrotoxicosis detected from laboratory tests on admission. Silent thyroiditis based on Hashimoto disease was diagnosed from the endocrinological evaluation. After a stent was implanted into left iliac vein, she discharged with anticoagulation therapy. Her thyroid hormone levels decreased under normal range in October 2010 and we started low dose of levothyroxine treatment and thyroid-stimulating hormone (TSH) was controlled within normal range around 1.5 U/ml. In November 2011, TSH level declined to 0.76 U/ml and dose of levothyroxine was reduced. The iliofemoral DVT recurred in December 2011 and apparent hyperthyroidism was observed. This suggests that silent thyroiditis had recurred just before the recurrence of DVT in this case.

Discussion: Specific stimulation of coagulation factor VIII (FVIII) by triiodothyronine is suggested to be a mechanism of thrombosis caused by thyrotoxicosis. It is known that serum level of von Willebrand factor, which elevated in this case, is one of the indicators for activity of FVIII. Previous studies indicated that thrombosis seems to occur in the circumstance existing not only thyrotoxicosis but also other factors that can induce thrombosis including OC taking and intravascular stents. Although we usually suppose that silent thyroiditis improves without any serious problems, this case shows us that it can induce thrombosis especially in patients who have high risk of thrombosis.