**1. Introduction**

Thrombosis is the leading cause of death in the world. Indeed, atherothrombosis including coronary artery diseases and cerebrovascular diseases is the top cause of death in various regions of the world [1]. Venous thrombosis including deep venous thrombosis and pulmonary embolism is the third cause of death in hospitalized patients [2]. Thrombosis is a disease caused by thrombi formed at various vessels. The major symptom differs substantially depending upon the site where the thrombi developed. Typically, arterial thrombosis such as myocardial infarction and ischemic stroke is symptomatic even when the thrombi are small (e.g., less than 1 mm in diameter) [3]. On the other hand, venous thrombosis is asymptomatic until thrombi become substantially large such as the ones that occlude several pulmonary arteries to cause pulmonary embolism [4]. In both arterial and venous thromboses, platelets are cells that contribute to initial thrombus formation. Coagulation and fibrinolysis are systems necessary to regulate the size of fibrin thrombi.

It is noteworthy that there is homogeneity in risk factors for various arterial/venous thromboses despite wide variation of clinical manifestation [5]. Framingham study demonstrated that cigarette smoking, diabetes mellitus (DM), dyslipidemia, and hypertension are strong predictors for the future onset of arterial thrombosis represented by acute myocardial infarction [6]. Recent international

registries also confirm that these risk factors are contributing factors for the recurrence of cardiovascular events [7]. Moreover, international registries also suggested these parameters as risk factors of venous thrombosis [8]. These clinical observations suggested the presence of common pathways for the onset of arterial and venous thrombosis [9].

The Framingham registry suggested the contributory role of obesity and less exercise as the predictors for future prevalence of risk factors. These abnormalities represented as visceral obesity-related syndrome is named as "metabolic syndrome." In metabolic syndrome patients, insulin resistance is one of the major contributors [10]. Increased body weight, high blood pressure, and dyslipidemia are common manifestations of metabolic syndrome. Long-term exposure to a highcalorie diet and lack of good exercise are supposed as underlining mechanisms for the onset of metabolic syndromes. The risk of thrombotic disease including arterial and venous thrombosis is speculated to be high in patients with metabolic syndrome.
