The association between TSH and thyroid hormones in the normal or subclinical dysfunction range with left ventricular...

Area of Science:

• Cardiology
• Endocrinology
• Thyroidology

Background:

• Thyroid hormones significantly influence cardiovascular function.
• The precise impact of subclinical thyroid dysfunction and euthyroid thyroid hormone levels on cardiac function remains incompletely understood.
• Left ventricular (LV) diastolic dysfunction is a critical indicator of cardiac health.

Purpose of the Study:

• To investigate the association between subclinical thyroid dysfunction and LV diastolic dysfunction.
• To explore the relationship between thyroid hormones within the normal reference range and cardiac function.
• To clarify the role of subclinical hypothyroidism and subclinical thyrotoxicosis in diastolic dysfunction.

Main Methods:

• A cross-sectional study involving 26,289 participants from the Republic of Korea.
• Participants were categorized into euthyroid, subclinical hypothyroidism, and subclinical thyrotoxicosis groups based on thyroid-stimulating hormone (TSH), free thyroxine (FT4), and triiodothyronine (T3) levels.
• Cardiac structure and function, specifically LV diastolic dysfunction, were assessed using echocardiography.

Main Results:

• Subclinical hypothyroidism was significantly associated with increased odds of LV diastolic dysfunction (adjusted odds ratio [AOR] 1.36).
• Subclinical thyrotoxicosis did not show a significant association with LV diastolic dysfunction.
• Serum triiodothyronine (T3) levels within the normal range were inversely associated with LV diastolic dysfunction, suggesting a more significant role than TSH or FT4.

Conclusions:

• Subclinical hypothyroidism is a significant risk factor for developing left ventricular diastolic dysfunction.
• Subclinical thyrotoxicosis does not appear to be associated with LV diastolic dysfunction.
• Serum T3 levels, even within the normal range, play a notable role in modulating LV diastolic function.