Circulating adiponectin levels and risk of endometrial cancer: Systematic review and meta-analysis

Previous epidemiological studies have presented conflicting results regarding associations between circulating adiponectin (APN) levels and the risk of endometrial cancer. Thus a meta-analysis was performed to investigate the association between these factors. Multiple electronic sources, including PubMed, SpringerLink and Google Scholar data-bases were searched to identify relevant studies for the present meta-analysis. All of the selected studies examined the correlation between circulating APN levels and endometrial cancer. The standardized mean difference (SMD) and 95% confidence intervals (CIs) were estimated and pooled using meta-analysis methods. Overall, 18 case-control studies met the inclusion criteria. A total of 5,692 participants and 2,337 cases of endometrial cancer were included in this meta-analysis. The SMD of the pooled analysis (95% CI) were -1.96 (-2.60, -1.31), P=0.000. When the cancer grades were compared, the APN values were not significantly different between the grades of endometrial cancer [G1 vs. G3, 1.02 (-0.68, 2.72), P>0.05; G1 vs. G2, 0.34 (-0.86, 1.54), P>0.05]. However, there was a significant association between high APN levels and postmenopausal endometrial cancer cases with an SMD (95% CI) of -2.27 (-4.36, -0.18) and P<0.05, however, no association was observed in premenopausal endometrial cancer cases with an SMD (95% CI) of -1.52 (-3.49, 0.45) and P>0.05. The low circulating APN level increases the risk of endometrial cancer, whereas the high APN level decreases this risk in postmenopausal women. Circulating APN as simple biomarkers may be a promising tool for the prevention, early diagnosis and disease monitoring of endometrial cancer.