Exogenous subclinical hyperthyroidism impairs endothelial function in nodular goiter patients.

Area of Science:

• Endocrinology
• Cardiovascular Medicine
• Metabolic Health

Background:

• Subclinical hyperthyroidism from exogenous levothyroxine (LT4) is linked to cardiovascular and metabolic alterations.
• Euthyroid nodular goiter (MNG) patients are often treated with LT4 for TSH suppression.

Purpose of the Study:

• To investigate the impact of LT4-induced TSH suppression on endothelial function and insulin sensitivity.
• To assess changes in oxidative stress and inflammation markers in MNG patients undergoing LT4 therapy.

Main Methods:

• A study involving 22 euthyroid MNG patients and 22 healthy controls.
• LT4 administration to achieve serum TSH <0.5 mIU/L for 8 weeks, measuring flow-mediated vasodilatation (FMD), insulin sensitivity index (ISI), lipid peroxidation (Tbars), and hsCRP.

Main Results:

• LT4 effectively suppressed TSH levels in MNG patients.
• Significant reductions in FMD (p < 0.001) and ISI (p < 0.001) were observed.
• Increased lipid peroxidation (Tbars, p < 0.05) and hsCRP (p < 0.001) indicated heightened oxidative stress and inflammation.

Conclusions:

• TSH suppression with LT4 in euthyroid MNG patients induces subclinical hyperthyroidism.
• This condition is associated with impaired endothelial function, increased oxidative stress, and reduced insulin sensitivity.
• Findings suggest careful monitoring for cardiovascular and metabolic changes during LT4 therapy.