Shu X, et al. - Since central obesity and circulating fasting insulin and glucose have been linked to breast cancer development, researchers assessed the links between breast cancer risk and fasting insulin, fasting glucose, 2-hour glucose, body mass index (BMI) and BMI-adjusted waist-hip-ratio (WHRadj BMI) using Mendelian randomization analyses. The formerly described inverse correlation of genetically predicted BMI with breast cancer risk was confirmed in this study. Moreover, findings revealed a positive correlation between genetically predicted fasting insulin and 2-hour glucose; an inverse correlation of WHRadj BMI with breast cancer risk was also found. An essential role of genetically determined obesity and glucose/insulin-related characteristics was suggested in the etiology of breast cancer.