Thyroid cancer is the most common endocrine malignancy, and its incidence has increased rapidly over the past decade.1,2 The Chinese Cancer Registry indicates that thyroid cancer occurs 6.6 times per 100 000 individuals and is the sixth most common malignant tumor among women in China.3 Approximately 95% of thyroid cancers are differentiated thyroid cancers (DTCs), which include both papillary and follicular thyroid cancers.4 The classical treatment for DTC involves thyroidectomy followed by radioactive iodine remnant ablation and thyroid-stimulating hormone (TSH) suppression therapy.5,6 TSH suppression therapy with levothyroxine is intended to reduce the recurrence rate and cancer-related mortality in patients with DTC.6 However, iatrogenic hyperthyroidism produced by TSH suppression therapy may lead to adverse outcomes such as osteoporosis, fractures, and cardiovascular disease.7, 8, 9, 10, 11

Some studies have revealed that long-term TSH suppressive therapy may affect cardiac structure and function; however, no consensus has been reached. Several studies12, 13, 14 have reported that patients who received TSH suppressive therapy had higher interventricular septal thicknesses (IVSTs), left ventricular posterior wall thicknesses (LVPWTs), and left ventricular mass indexes (LVMi) compared to healthy controls; however, others15, 16, 17 have claimed similar IVST, LVPWT, and LVMi values in both groups of patients. Smit et al16 have reported that TSH suppressive therapy in DTC might induce cardiac diastolic dysfunction; however, this was not observed by Hong et al18 Abdulrahman et al19 have found a decreased left ventricular ejection fraction (LVEF) in patients with DTC who received TSH suppression therapy following thyroidectomy, implying a decreased cardiac systolic function that was inconsistent with the findings of Taillard et al20 Despite several clinical studies, no systematic review or meta-analysis has investigated whether long-term TSH suppression therapy is linked to adverse cardiac effects following thyroidectomy, in patients with DTC. Therefore, this meta-analysis aimed to investigate the effects of long-term TSH suppression therapy on cardiac structure and function.