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Low-Normal Thyroid Function and Novel Cardiometabolic Biomarkers
- van Tienhoven-Wind, Lynnda J.N., Dullaart, Robin P.F.
- Nutrients 2015 v.7 no.2 pp. 1352-1377
- adverse effects, antioxidants, bilirubin, biomarkers, cardiovascular diseases, fatty liver, functional status, high density lipoprotein cholesterol, hyperglycemia, insulin resistance, low density lipoprotein cholesterol, nutrition risk assessment, pathogenesis, protein metabolism, thyroid function, thyrotropin, thyroxine, triacylglycerols
- The concept is emerging that low-normal thyroid function, i.e., either higher thyroid-stimulating hormone or lower free thyroxine levels within the euthyroid reference range, could contribute to the development of atherosclerotic cardiovascular disease. It is possible that adverse effects of low-normal thyroid function on cardiovascular outcome may be particularly relevant for specific populations, such as younger people and subjects with high cardiovascular risk. Low-normal thyroid function probably relates to modest increases in plasma total cholesterol, low density lipoprotein cholesterol, triglycerides and insulin resistance, but effects on high density lipoprotein (HDL) cholesterol and non-alcoholic fatty liver disease are inconsistent. Low-normal thyroid function may enhance plasma cholesteryl ester transfer, and contribute to an impaired ability of HDL to inhibit oxidative modification of LDL, reflecting pro-atherogenic alterations in lipoprotein metabolism and HDL function, respectively. Low-normal thyroid function also confers lower levels of bilirubin, a strong natural anti-oxidant. Remarkably, all these effects of low-normal thyroid functional status appear to be more outspoken in the context of chronic hyperglycemia and/or insulin resistance. Collectively, these data support the concept that low-normal thyroid function may adversely affect several processes which conceivably contribute to the pathogenesis of atherosclerotic cardiovascular disease, beyond effects on conventional lipoprotein measures.