Low-normal thyroid function and novel cardiometabolic biomarkers

• Published in: Nutrients 2015-02, Vol.7 (2), p.1352-1377
• Main Authors: van Tienhoven-Wind, Lynnda J N, Dullaart, Robin P F
• Format: Article
• Language: English
• Subjects: Age; Aged; Atherosclerosis; bilirubin; Biomarkers; Biomarkers - blood; biomarkers, cardiovascular disease; Cardiovascular disease; Cardiovascular Diseases - blood; Cardiovascular Diseases - diagnosis; Carrier Proteins - blood; Cholesterol; Cholesterol - blood; cholesteryl ester transfer; dyslipidemia; Female; Heart attacks; High density lipoprotein; Humans; Hypothyroidism; Insulin Resistance; Ischemia; lipids; Lipoproteins, HDL - blood; Liver diseases; Low density lipoprotein; Male; Metabolic syndrome; Middle Aged; Mortality; non-alcoholic fatty liver disease; Pathogenesis; Plasma; Predictive Value of Tests; Risk Factors; subclinical hypothyroidism; Thyroid Function Tests; Thyroid gland; Thyroid Gland - metabolism; thyroid hormones; Thyrotropin - blood; Thyroxine - blood; Triglycerides; Triglycerides - blood
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu7021352

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.