Subclinical hypothyroidism and dilated cardiomyopathy (DCM) in children

Introduction: Subclinical hypothyroidism is defined by the combination of an elevated thyroid-stimulating hormone (TSH) level and a normal free thyroxine (T4L) level.
Dilated cardiomyopathy is characterized by both dilation of the ventricles and hypokinesia of these ventricles. It predominantly involves the left ventricle, but the right ventricle is frequently involved.We present two cases of idiopathic dilated cardiomyopathy associated with a subclinical picture of hypothyroidism.
Case report 1: An 11-year-old female patient was admitted to cardiology for congestive heart failure on CMD; she presented with New York Heart Association (NYHA) stage IV dyspnea and generalized edema. Tran’s thoracic echocardiography showed left ventricular (LV) dilatation with global hypokinesia, LV ejection fraction at 15%. The biological workup showed a subclinical hypothyroidism profile with TSH at 11.2 mIU/l, T4: 21.2 pmol/l, T3: 4.2pmol/l.
Case report 2: A 9-year-old patient, without any notable history, was referred to the cardiology department for global cardiac decompensation with NYHA stage IV dyspnea and lower limb edema despite optimal medical treatment. Tran’s thoracic echocardiography showed dilated cardiomyopathy with severe impairment of LV systolic function (10%). The biological workup showed a subclinical hypothyroidism profile with TSH: 7.7 mIU/l, T4: 19.2 pmol/l.
Conclusion: Dilated cardiomyopathies (DCM) represent the most common cardiomyopathies in children either of constitutional or acquired origin. Subclinical hypothyroidism is frequently observed in patients with DCM and increases the risk of mortality.