Association Between Cardiovascular Risk Factors and Serum Thyrotropin Concentration Among Healthy Chinese Subjects and Subjects with Unsuspected Subclinical Hypothyroidism.

ABSTRACT

BACKGROUND: Even within the reference range, thyrotropin (TSH) levels were found to be positively associated with the risk of cardiovascular disease (CVD). However, the underlying mechanism of TSH remains ambiguous. This study investigated the association of TSH with cardiovascular risk factors among healthy Chinese subjects and subjects with unsuspected subclinical hypothyroidism (SCH). METHODS: A total of 741 subjects were included in this cross-sectional study. The subjects were grouped into four, including tertile groups for the TSH reference range and an SCH group based on the TSH level. All the participants underwent physical examination and fasting blood analyses to determine the levels of TSH, free thyroxine, free triiodothyronine, plasma glucose, triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein A1, apolipoprotein B (ApoB), lipoprotein(a), homocysteine (Hcy), and high sensitivity C-reactive protein (hs-CRP). RESULTS: The TSH subgroups exhibited a significant increasing trend in terms of LDL-C, ApoB, and Hcy levels (p = 0.01, p < 0.01, and p = 0.01, respectively), whereas the HDL-C levels exhibited a decreasing trend (p = 0.03). After adjusting for gender, age, and smoking status, the TSH levels were found to be positively correlated with body mass index, waist circumference, diastolic blood pressure (DBP), and TG, TC, LDL-C, ApoB, Hcy, and hs-CRP levels (p < 0.05 for all), but negatively correlated with the HDL-C levels (p < 0.01). Multiple linear regression analysis showed that the TSH levels were independently positively associated with the female gender (ß = 0.21, p < 0.01), DBP (ß = 0.14, ß = 0.01), and Hcy levels (ß = 0.10, p = 0.01), and negatively associated with the HDL-C (ß = -0.11, p = 0.01) and FT4 levels (ß = -0.15, p < 0.01). CONCLUSIONS: The TSH levels were independently associated with several cardiovascular risk factors in an apparently healthy Chinese population, and thus may increase the risk of CVD.