Objective: The diagnosis of subclinical central hypothyroidism in hypothalamic-pituitary patients cannot be established by serum markers of thyroid hormone action. Myocardial function by echocardiography has been shown to reflect thyroid hormone action in primary thyroid dysfunction. We evaluated the performance of echocardiography in diagnosing subclinical central hypothyroidism. Design: Cross-sectional and before and after. Methods: Echocardiography and serum thyroid hormones were assessed in overt primary (nZ20) and central (nZ10) hypothyroidism, subclinical primary hypothyroidism (nZ10), hypothalamic-pituitary disease with normal free thyroxine (FT 4 ; nZ25), and controls (nZ28). Receiver operating characteristic (ROC) curves were generated using overt hypothyroidism patients and selected cut-off values were applied to detect both primary and central subclinical hypothyroidism. After levothyroxine (L-T 4 ) intervention, patients were echocardiographically reevaluated at predefined targets: normal thyrotropin (TSH) in primary hypothyroidism, normal FT 4 in overt central hypothyroidism, and higher than pretreatment FT 4 in echo-defined subclinical central hypothyroidism.