BackgroundGlucocorticoids play an important role in cardiac physiology. Chronic exposure and higher doses may cause adverse effects on the myocardium, especially in young patients receiving long‐term therapy.ObjectiveTo assess cardiac function in children with congenital adrenal hyperplasia (CAH) and its relation to glucocorticoid dose and therapy duration.MethodsForty‐seven patients with CAH due to 21‐hydroxylase deficiency were compared to 47 controls. Patients were subdivided according to treatment duration (Group A: less than 6 years, Group B: more than 6 years). Mean daily glucocorticoid and cumulative glucocorticoid doses were calculated. Echocardiography was performed for patients and controls to evaluate cardiac functions, chamber dimensions and tissue Doppler valvular status.ResultsCompared to controls, patients had cardiac chamber hypertrophy reflected by higher M‐mode dimensions. Patients had lower fractional shortening, defective ventricular relaxation, lower average mitral and tricuspid e´/a´ ratios (e´ early diastolic, a´ late diastolic) as well as s´ (systolic) velocities, higher average mitral E/e ratio and higher left ventricle TDI Tei index (P < .05). Group B had lower average mitral e´/a´ and tricuspid s´ velocities, and higher average mitral E/e ratio (P < .05). Cumulative glucocorticoid dose significantly correlated with different echocardiographic parameters.ConclusionLong‐term glucocorticoid therapy even within the recommended therapeutic range adversely affects cardiac functions in children with 21‐hydroxylase deficiency.