Background: Subclinical hyperthyroidism is defined by a subnormal serum thyroidstimulating
hormone (TSH) level with normal free thyroxine (FT4) and free triiodothyronine (FT3)
levels. Its prevalence varies from 0.6% to 16% in the elderly and can increase to 20% in patients receiving
thyroid hormone replacement therapy. Thyroid disease and/or replacement therapy are frequently
associated with cardiovascular involvement.
Cases Presentation: We report three clinical cases of patients with initial subclinical hyperthyroidism
and cardiological manifestations, including supraventricular and ventricular extrasystoles, prolapse of
the mitral valve with severe regurgitation, higher mean heart rate and deterioration of the arrhythmias
on arrhythmogenic dysplasia substrate.
Conclusion: We discuss the role of appropriate and early correction of thyroid dysfunction in improving
Keywords: Subclinical hyperthyroidism, heart disease, arrhythmia, mitral valve insufficiency, accessory pathway, l-thyroxine.
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