Abstract

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 (n=20) and central (n=10) hypothyroidism, subclinical primary hypothyroidism (n=10), hypothalamic-pituitary disease with normal free thyroxine (FT4) (n=25) and controls (n=28). Receiver-operating-characteristic (ROC) curves were generated using overt hypothyroidism patients and selected cut-offs were applied to detect both primary and central subclinical hypothyroidism. After levothyroxine intervention, patients were echocardiographically reevaluated at predefined targets: normal thyrotropin in primary hypothyroidism, normal FT4 in overt central hypothyroidism, and higher than pretreatment FT4 in echo-defined subclinical central hypothyroidism.Results: Parameters with highest areas under the ROC curves (AUC≥0.94) were: isovolumic contraction time, isovolumic contraction time/ejection time, and myocardial performance index. Highest diagnostic accuracy (93%) was obtained when at least one parameter was increased (positive and negative predictive values: 93%). Hypothyroidism was echocardiographically diagnosed in 8 of 10 patients with subclinical primary hypothyroidism and in 14 of 25 patients (56%) with hypothalamic-pituitary disease and normal serum FT4. Echocardiographic abnormalities improved significantly after levothyroxine and correlated (0.05<P<0.001) with changes in FT4 (-0.62<r<-0.55) and thyrotropin (0.63<r<0.68) in primary hypothyroidism and with FT4 in central hypothyroidism (-0.72<r<-0.50).Conclusion: Echocardiography can be useful in diagnosing subclinical central hypothyroidism in patients with hypothalamic-pituitary disease.