Low-normal thyroid function and novel cardiometabolic biomarkers.

Area of Science:

• Endocrinology
• Cardiovascular Medicine
• Metabolic Syndrome

Background:

• Emerging evidence suggests subclinical thyroid dysfunction may impact cardiovascular health.
• Low-normal thyroid function, defined by thyroid-stimulating hormone (TSH) or free thyroxine (fT4) within euthyroid ranges, is increasingly recognized as a potential risk factor.

Purpose of the Study:

• To explore the association between low-normal thyroid function and atherosclerotic cardiovascular disease (ASCVD).
• To investigate the specific mechanisms linking low-normal thyroid function to pro-atherogenic changes, particularly in at-risk populations.

Main Methods:

• Review of existing literature and data on thyroid function, lipoprotein metabolism, insulin resistance, and cardiovascular outcomes.
• Analysis of how low-normal thyroid function influences lipid profiles, high-density lipoprotein (HDL) functionality, and antioxidant levels like bilirubin.

Main Results:

• Low-normal thyroid function is linked to increased total cholesterol, LDL cholesterol, triglycerides, and insulin resistance.
• It may impair HDL's ability to inhibit LDL oxidation and is associated with lower bilirubin levels, a key antioxidant.
• These effects are exacerbated in individuals with chronic hyperglycemia or insulin resistance.

Conclusions:

• Low-normal thyroid function contributes to pro-atherogenic alterations in lipoprotein metabolism and HDL function.
• It represents a potential, underappreciated risk factor for atherosclerotic cardiovascular disease, especially in vulnerable populations.
• Further research is warranted to elucidate the clinical implications and therapeutic targets for low-normal thyroid function in cardiovascular disease prevention.