Abstract
OBJECTIVE: L-Thyroxine-suppressive therapy benefits high-risk differentiated thyroid cancer patients by decreasing recurrence rates and cancer-related mortality. However, fully suppressed serum thyroid-stimulating hormone (TSH) implies a state of subclinical hyperthyroidism (SCH) with associated adverse cardiac effects. Because left ventricular (LV) diastolic dysfunction may be the first manifestation of more severe LV failure, and to balance the risks from thyroid cancer recurrence with risks of cardiac failure, the purpose of this study was to analyse new parameters of LV function in asymptomatic patients with exogenous SCH. DESIGN: Case-control study with 24 patients on TSH-suppressive therapy of short duration (≤ 4 years) after thyroid ablative therapy for differentiated thyroid carcinoma and 20 age- and sex-matched subjects. MEASUREMENTS: LV function [LV global strain and strain rate (SR) curves] was assessed by speckle tracking imaging echocardiography in each subject. RESULTS: Patients and controls do not differ in body mass index, systolic blood pressure and heart rate. No significant differences were observed in LV morphology (LV mass and relative wall thickness), cardiac output and parameters of LV systolic function between patients on suppressive therapy and controls. When compared with controls, patients with exogenous SCH had a significantly impaired longitudinal protodiastolic strain, SR and strain diastolic index but preserved radial strain and SR function. CONCLUSIONS: In subjects with SCH at the early phase of TSH-suppressive therapy, evidence of isolated longitudinal LV diastolic dysfunction was observed, despite a normal LV morphology. Further prospective studies to clarify the prognosis of picking-up early diastolic dysfunction in asymptomatic patients are needed before serial measurements could be recommended.