Both hypothyroidism and hyperthyroidism enhance low density lipoprotein oxidation

Area of Science:

• Endocrinology
• Cardiovascular Medicine
• Biochemistry

Background:

• Hypothyroidism is linked to hypercholesterolemia and atherosclerosis risk.
• Hyperthyroidism can trigger angina or myocardial infarction in patients with coronary heart disease.
• Thyroid hormones, specifically L-T4, exhibit antioxidant properties and inhibit LDL oxidation in vitro.

Purpose of the Study:

• To evaluate changes in low-density lipoprotein (LDL) oxidation in individuals with hypothyroidism and hyperthyroidism.
• To assess the impact of thyroid dysfunction on LDL susceptibility to oxidation.
• To compare LDL oxidation status in hypothyroid, hyperthyroid, and euthyroid states.

Main Methods:

• Collected fasting blood samples for LDL oxidation analysis, lipoprotein determination, and thyroid function tests.
• Measured the lag phase of copper-catalyzed LDL oxidation.
• Compared oxidation parameters between hypothyroid, hyperthyroid, and euthyroid states, including post-treatment euthyroid states.

Main Results:

• The lag phase of LDL oxidation was significantly shorter in hypothyroid (4 h) and hyperthyroid (6 h) states compared to euthyroid states (14 h and 12 h, respectively).
• Total and LDL cholesterol levels were elevated in hypothyroidism and reduced in hyperthyroidism relative to euthyroid states.
• Restoring euthyroid states significantly increased the lag phase of LDL oxidation, indicating reduced susceptibility.

Conclusions:

• LDL exhibits increased susceptibility to oxidation in both hypothyroid and hyperthyroid conditions.
• Enhanced LDL oxidation may contribute to the pathogenesis of cardiac disease in thyroid dysfunction.
• Therapeutic normalization of thyroid hormone levels (euthyroid state) mitigates the increased susceptibility of LDL to oxidation.