Both Exogenous Subclinical Hyperthyroidism and Short-Term Overt Hypothyroidism Affect Myocardial Strain in Patients with Differentiated Thyroid Carcinoma

Background: The cardiovascular effects of transitions from exogenous subclinical hyperthyroidism to short-term overt hypothyroidism in patients treated for differentiated thyroid carcinoma remain unclear. The present study aims at evaluating the changes in multidirectional myocardial strain using two-dimensional (2D) speckle tracking during this controlled transition from exogenous subclinical hyperthyroidism to overt hypothyroidism. Methods: The study included 14 patients with differentiated thyroid carcinoma on thyrotropin suppressive thyroxine substitution who were subsequently withdrawn from thyroxine for 4 weeks. Cardiac function was assessed by 2D speckle tracking echocardiography before and 1 and 4 weeks after withdrawal and compared with values obtained in a control group of 24 individuals. Results: At baseline, the left ventricular dimensions were significantly higher in patients as compared with controls. Using 2D speckle tracking imaging, the patients had significantly impaired baseline myocard...