Dilated Cardiomyopathy Following Total Thyroidectomy Complicated by Severe Mitral Regurgitation: A Case Report and Literature Review

Abstract : Cardiac dysfunction following thyroid and parathyroid surgery is rare but clinically significant. Hormonal disturbances, including iatrogenic hypothyroidism and calcium metabolism disorders, may adversely affect myocardial function and the mitral valve. We report the case of a 56-year-old woman who underwent thyroidectomy and parathyroidectomy in 2024. One year later, after discontinuation of thyroid hormone replacement and calcium supplementation, she progressively developed dyspnea, peripheral edema, and heart failure. Transthoracic echocardiography revealed hypokinetic dilated cardiomyopathy (left ventricular ejection fraction [LVEF] 32%) associated with severe functional mitral regurgitation. Laboratory tests showed marked hypothyroidism (TSH 95 µIU/mL, free T4 2.39 pmol/L), hypocalcemia (total calcium 43 mg/L), and elevated NT-proBNP levels (7,850 ng/L). Management combined guideline-directed medical therapy for heart failure, gradual thyroid hormone replacement, calcium supplementation, and discussion of potential surgical/valvular intervention. After six months of follow-up, a significant improvement in cardiac function and regression of mitral regurgitation were observed. This case highlights the importance of cardiologic and endocrinologic surveillance after thyroid and parathyroid surgery. Early recognition of hormonal abnormalities and cardiac dysfunction is crucial to optimize management and improve prognosis.