The Relation of Thyroid Function to Components of the Metabolic Syndrome in Korean Men and Women

This study was to assess the relation of thyroid dysfunction to metabolic syndrome (MetS) at an earlier stage in Korean population. Metabolic parameters such as body composition, blood pressure (BP), fasting glucose, total cholesterol, triglyceride (TG), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), thyroid-stimulating hormone (TSH) and free thyroxine 4 (fT(4)) were measured. During a mean follow-up of 3 yr, 5,998 Koreans ages over 18 yr were assessed. There were 694 cases of MetS at follow-up. The mean age of the subjects was 45.6 +/- 9.5 yr. Mean level of TSH was 2.02 +/- 1.50 mlU/L, mean level of fT(4) was 1.23 +/- 0.20 pM/L. At baseline, TSH levels and fT(4) levels were associated to waist circumference, BP, glucose and lipids in the subjects. Increase in systolic blood pressure, diastolic blood pressure (DBP), total cholesterol and TG were significantly associated with changes in TSH levels after adjustment. Changes in DBP, TG, HDL-C and fasting glucose were significantly associated with changes in fT(4) levels after adjustment. Increase in TSH levels even after further controlling for baseline TSH level predicted the MetS over the study period. In conclusion, there is a relationship between thyroid function and cardiovascular risk factors, such as BP, total cholesterol, TG, HDL-C and fasting glucose. Also, higher levels of TSH may predict the MetS in Korean.