Thyroid hormone and the heart
Date
2002
Authors
Moolman J.A.
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Abstract
Thyroid hormone has important cardiovascular effects, and abnormalities of its production cause cardiovascular morbidity. The role of both excessive and insufficient thyroid hormone production in the pathogenesis of clinical cardiac diseases can be deduced from thyroid hormone-induced molecular changes. Thyroid hormone regulates the expression of myocardial genes regulating the handling of calcium, which affects both systolic and diastolic myocardial function. Thyroid hormone also has indirect and direct effects on peripheral vascular smooth muscle tone, and alters the coupling of the left ventricle and arterial system. Excessive production of thyroid hormone results in an increased cardiac output as well as increased cardiac work efficiency, but reduced cardiac reserve. Amiodarone therapy for cardiac rhythm can cause both hyper- and hypothyroidism. Amiodarone-induced thyrotoxicosis (AIT) can be due to either excessive thyroid hormone production (type I AIT) or thyroid hormone release due to an inflammatory condition (type II AIT). Classification of AIT is helpful in guiding therapy. Amiodarone causes changes in the thyroid function tests of euthyroid patients on therapy - it inhibits the conversion of T4 to T3, which results in decreased T3 and slightly increased T4 serum levels in euthyroid patients. Baseline thyroid functions should therefore be determined before starting amiodarone therapy, and at 6-monthly intervals thereafter.
Description
Keywords
amiodarone, calcium, liothyronine, thyroid hormone, thyroxine, calcium transport, cardiovascular disease, cardiovascular effect, cardiovascular risk, diastolic blood pressure, disease classification, gene expression regulation, heart arrhythmia, heart left ventricle, heart output, human, hyperthyroidism, hypothyroidism, morbidity, pathogenesis, review, smooth muscle tone, systolic blood pressure, thyroid function, thyroid hormone synthesis, thyrotoxicosis, thyroxine blood level, Amiodarone, Anti-Arrhythmia Agents, Cardiovascular System, Heart, Humans, Hyperthyroidism, Hypothyroidism, Thyroid Function Tests, Thyroid Gland, Thyroid Hormones, Thyrotoxicosis
Citation
Cardiovascular Journal of South Africa
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