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[Heart and thyroid]
1CHU de Nancy, Clinique Médicale et Endocrinologique, Vandoeuvre-les-Nancy.
Insights
Thyroid hormones significantly impact cardiovascular health, affecting heart function and circulation. Both hyperthyroidism and hypothyroidism can lead to serious cardiac complications, necessitating careful management.
Area of Science:
- Cardiovascular Physiology
- Endocrinology
Context:
- Thyroid hormones play a crucial role in regulating cardiovascular function.
- Both excess (hyperthyroidism) and deficiency (hypothyroidism) of thyroid hormones have profound effects on the heart and blood vessels.
Purpose:
- To elucidate the cardiovascular actions of thyroid hormones.
- To describe the cardiovascular manifestations and complications associated with hyperthyroidism and hypothyroidism.
Summary:
- Thyroid hormones influence myocardial contractility, relaxation, sympathetic nervous system interaction, and peripheral circulation.
- Hyperthyroidism increases myocardial contractility, cardiac output, and decreases vascular resistance, potentially leading to high-output heart failure, arrhythmias, and mitral valve prolapse.
- Hypothyroidism is linked to bradycardia, reduced cardiac output, increased vascular resistance, elevated cholesterol, atherosclerosis, angina, hypertension, and heart blocks.
Impact:
- Understanding these effects is vital for diagnosing and managing cardiovascular complications in thyroid disorders.
- Highlights the importance of monitoring cardiovascular health in patients with subclinical or overt thyroid dysfunction.
- Informs treatment strategies, including the use of sympathetic blocking agents for hyperthyroidism.
Abstract:
Thyroid hormones may exert cardiovascular actions by direct effects on the myocardium, by interacting with the sympathetic nervous system and through alterations of the peripheral circulation. Then, thyroid hormones increase myocardial contractility and relaxation, sensitise the myocardium to sympathetic nervous system and decrease arterial resistance. Hyperthyroidism results in an enhanced myocardial contractility, an increased cardiac output and a fall in systemic vascular resistance. Nevertheless "high output" cardiac decompensation may occur. Thyrotoxicosis may trigger arrythmia and disease seems to be associated with an increase in the frequency of mitral valve prolapse. Even in mild or subclinical hyperthyroidism complication may occur. Sympathetic blocking agents are the treatment of choice in addition to aetiologic treatment. Hypothyroidism is associated with bradycardia, a decreased cardiac output, increased vascular resistance and perhaps a decreased sensitivity of the sympathoadrenal system. An increase in cholesterolemia leads to an additional risk for the development of atherosclerosis. Main cardiovascular complications of hypothyroidism are angina pectoris, diastolic hypertension, atrio-ventricular blocks or pericarditis. Mild hypothyroidism might also be correlated with an increase in adverse effects.