Subclinical Hypothyroidism in India: An Imperative Risk for Coronary Artery Disease (CAD)

Accurate diagnosis and treatment of subclinical hypothyroidism (SCH) is challenging in clinical practice because normal limits of TSH differs in various studies [1]. Subclinical Hypothyroidism (SCH) is defined as mild elevation in serum TSH levels with normal fT3 and fT4 concentration. The prevalence of this disease is 4-10% in the general population of United States. Up to 20 % women older than 60 years of age are affected with subclinical hypothyroidism in their study [2,3]. It is also known that the SCH is more prevalent in elderly age group (over 50 years) because TSH increases with age [4]. The disease is more common in women than in men. Franklyn has shown its prevalence in women (7.5 %) than in men where occurrence was only 2.8% of total population [5]. The importance of sub marginal elevation of TSH values is not known however elevated levels are associated with abnormalities of lipid metabolism (increased total cholesterol and low density lipoprotein cholesterol) that can lead to coronary artery disease and depression [6,7]. It is also associated with endothelial dysfunction [8], aortic atherosclerosis and myocardial infarction [9]. A search of database of Medline and Embase by Rodondi et al. [10] has suggested that subclinical hypothyroidism is associated with an increased risk of coronary heart disease [10]. According to them, subclinical hypothyroidism is associated with an increased risk of CHD events and CHD mortality in with higher TSH levels, particularly in those with TSH of 10 μIU/L. This report has shown the implication of SCH as a risk factor for CAD. The study was compiled from the data of 11 prospective cohorts in the United States, Europe, Australia, Brazil, and Japan [10]. There is paucity of similar information from developing countries like India. Therefore this study was planned to assess the prevalence of subclinical hypothyroidism in healthy urban population of India belonging to mid to high socioeconomic strata and the risk of coronary artery disease in affected individuals.