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The objective of this investigation is to explore a possible role of thyroid dysfunction in venous thromboembolism (VTE). The number of patients discharged from short-stay nonfederal hospitals in the United States, from 1979 to 2005, with a diagnostic code for hypothyroidism or hyperthyroidism, pulmonary embolism (PE), and deep venous thrombosis (DVT) was obtained from the National Hospital Discharge Survey (NHDS). Among 19,519,000 hospitalized patients discharged with a diagnosis of hypothyroidism from 1979 to 2005, 119,000 (0.61%) had PE. Among patients with no thyroid dysfunction, PE was diagnosed in 3,372,000 of 908,805,000 patients (0.37%; relative risk = 1.64, 95% CI 1.63-1.65). Deep venous thrombosis was diagnosed in 1.36% of hypothyroid patients and in 0.84% of patients with no thyroid dysfunction (relative risk = 1.62, 95% CI 1.61-1.62). The relative risk of PE in patients with hypothyroidism was highest in patients <40 years of age (relative risk = 3.99) and the relative risk of DVT was also highest in patients <40 years (relative risk = 2.25). Hyperthyroidism was not associated with an increased risk of VTE (relative risk = 0.98, 95% CI = 0.96-1.01). In conclusion, an increased risk of PE, DVT, and VTE was shown in patients with hypothyroidism but not hyperthyroidism. Antithrombotic prophylaxis in patients with severe hypothyroidism, however, should be viewed with caution because of a possible hyperfibrinolytic state in such patients.

Ankle exercise increases venous blood velocity while supine, but the effect of ankle exercise on venous blood velocity while sitting is not known. In this investigation, we test the hypothesis that venous blood velocity can be increased while sitting by repetitive dorsiflexion of the foot. Time-averaged peak velocity (TAPV) in the popliteal vein of 20 healthy male volunteers was measured by pulsed Doppler ultrasound at rest and during ankle exercise in the supine and sitting positions. Right popliteal vein TAPV while supine at rest was 11 cm/second (sec) (95% confidence interval [CI] =9-13 cm/sec) and with ankle exercise it increased to 24 cm/sec (95% CI =20-28 cm/sec) (p<0.0001). With sitting at rest, right popliteal vein blood TAPV decreased from 11 cm/sec to 3 cm/sec (95% CI = 2-4 cm/sec) (p<0.0001). With ankle exercise while sitting, right popliteal vein TAPV increased to 18 cm/sec (95% CI =15-21 cm/sec) (p<0.0001). In conclusion, in both the supine and sitting positions, ankle exercise increased venous blood velocity, thereby transiently reducing a tendency toward venous stasis. Such ankle exercise might be useful in the prevention of stasis-induced deep venous thrombosis.