The Association Between Sub-Clinical Hypothyroidism and Metabolic Syndrome: A Population Based Study

The association of subclinical hypothyroidism and metabolic syndrome is debatable. We aimed to find out whether there was a correlation between subclinical hypothyroidism and or its components. Using the stratified, multistage probability cluster sampling method, with a probability in proportion to size procedure we randomly selected 1200 women, aged 18-45 years, from among reproductive aged women, living in urban areas of four randomly selected provinces of different geographic regions of Iran,. Each woman underwent an evaluation that included standardized history, physical exam, biochemical and hormonal assessment. Metabolic syndrome was defined according to the ATPΙΙΙ definition and subclinical hypothyroidism was diagnosed, based on serum concentration of more than the upper normal limit of TSH (mIU/l 4.5). The prevalence of metabolic syndrome in women with subclinical hypothyroidism was not significantly different in comparison to normal ones (19% vs. 16.8%), however the prevalence of two metabolic syndrome components (low HDL and high TG) was significantly more in those women. There was a negative significant association between serum concentration of TSH and HDL-C, after adjusting for age, BMI and HOMA-IR. Although this study did not find the relationship between subclinical hypothyroidism and metabolic syndrome, because of its correlation with some components of this syndrome, thyroid dysfunction can be considered as a risk factor for metabolic syndrome, and further investigations to confirm this are recommended.