Thyroid Hormone Replacement Therapy and Increased Ejection Fraction in Hypothyroidism-induced Dilated Cardiomyopathy: A Systematic Review and Meta-summary

ABSTRACT: Hypothyroidism-induced dilated cardiomyopathy (DCM) is a rare but potentially reversible cause of heart failure with reduced ejection fraction. Evidence regarding the extent and timing of myocardial recovery after thyroid hormone replacement remains limited to scattered case reports. This study aims to synthesize available evidence on left ventricular ejection fraction (LVEF) recovery following thyroid hormone replacement therapy in patients with hypothyroidism-induced DCM. A systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using PubMed, Scopus, and ScienceDirect from inception to November 2025. Eligible studies included case reports or case series involving patients with documented hypothyroidism, echocardiographically confirmed DCM (LVEF <40% with ventricular dilatation), and follow-up after initiation of thyroid hormone replacement therapy. Data were synthesized qualitatively using a meta-summary approach. Eleven studies comprising 12 patients were included. All patients presented with severe left ventricular systolic dysfunction, with baseline LVEF ranging from approximately 15%-28%. Levothyroxine, administered orally or intravenously with or without liothyronine, was the primary therapy. Follow-up durations ranged from 3 to 36 months. Achievement of euthyroid status was consistently associated with substantial improvement in left ventricular systolic function. Most patients fulfilled criteria for heart failure with improved ejection fraction, and complete recovery (LVEF ≥50%) occurred in the majority. Limited recovery was observed in one case with prolonged untreated hypothyroidism, suggesting possible irreversible myocardial remodeling. Hypothyroidism-induced DCM is predominantly a reversible metabolic cardiomyopathy. Thyroid hormone replacement therapy leads to significant improvement in left ventricular function in most patients, with reversibility influenced by the severity and duration of untreated hypothyroidism.