Circulating adipokines and risk of obesity related cancers: A systematic review and meta-analysis

•Circulating adiponectin and leptin were significantly associated with risk of cancer.•Adiponectin was inversely related with breast, colorectal, and endometrial cancer.•Leptin was associated with increased risk of endometrial and kidney cancer.•There was no relationship between circulating IL-6, TNF-α, and resistin and cancer. Obesity can influence on carcinogenesis through alterations in adipokines and subsequent inflammatory changes. This meta-analysis was aimed to comprehensively assess the association between circulating adipokines and risk of obesity-related cancers. Pubmed and Embase were searched up to October 2017 for observational studies investigating the relationship between adipokines and cancers. Pooled odds ratio and the corresponding 95% confidence interval was estimated through the meta-analysis using a random-effects model. Findings A total of 93 observational studies (adiponectin = 60, high molecular weight adiponectin = 9, leptin = 39, IL-6 = 16, TNF-α = 10, and resistin = 17) were included. Adiponectin was significantly associated with decreased risk of cancer (pooled OR 0.70, 95% CI 0.60–0.80; I2 = 71.9%; Pheterogeneity