We have performed genetic correlation and Mendelian randomization analyses using publicly available genome-wide association study (GWAS) data to identify endometrial cancer risk factors. These and previously established risk factors of endometrial cancer were then included in a multi-trait Bayesian GWAS analysis to detect endometrial cancer susceptibility variants, identifying three novel loci (7q22.1, 8q24.3 and 16q12.2); two of which were replicated in an independent endometrial cancer GWAS dataset. These loci are hypothesized to affect endometrial cancer risk through altered sex-hormone levels or through effects on obesity. Consistent with this hypothesis, several genes with established roles in these pathways (CYP11B1, CYP3A7, IRX3 and IRX5) were prioritized as candidate endometrial cancer risk genes by interrogation of quantitative trait loci data and chromatin capture assays in endometrial cell lines. The findings of this study identify additional opportunities for hormone treatment and further support weight loss to reduce the risk of developing endometrial cancer.