The prevalence of subclinical thyroid dysfunction and its association with metabolic syndrome in Taiwanese elderly

Background: The pathophysiology of thyroid function on lipid and glucose metabolism and blood pressure for subjects with thyroid disorder is well known; however, studies exploring the association between thyroid function and components of metabolic syndrome (MetS) in elderly subjects with subclinical thyroid dysfunction are limited. Our objectives were to investigate the prevalence of subclinical thyroid dysfunction among the elderly and its relationship with MetS in Taiwan. Methods: A total of 6,652 subjects aged 65 years or older were recruited during a routine health checkup at four MJ Health Screening Centers in Taiwan. Gender; blood pressure; body mass index; and serum levels of fasting glucose, total cholesterol (TC), high-density-lipoprotein cholesterol (HDL-C), low-density-lipoprotein cholesterol, and triglyceride were compared between subjects with subclinical hypothyroidism and hyperthyroidism. Results: The overall prevalences of the MetS, subclinical hyperthyroidism, and subclinical hypothyroidism were 30.4%, 6.0%, and 2.0%, respectively. The prevalence of subclinical thyroid dysfunction was significantly higher among women as compared with men (9.9% vs. 6.3%, respectively; p < 0.05). Male subjects with subclinical hyperthyroidism had significantly lower body mass index, systolic blood pressure, TC, low-density-lipoprotein cholesterol, HDL-C, triglyceride, and number of MetS criteria than female subjects. However, no significant differences for each component of MetS, with the exception of TC and HDL-C, were found between male and female subjects with subclinical hypothyroidism. Conclusion: Subclinical thyroid dysfunction would present in about 8% of Taiwanese elderly, and about one-third of them had MetS.