The adipose tissue also regulates the production of sex hormones [38] which are considered to mediate the association of adiposity with breast cancer risk by expressing aromatase enzymes, and by increasing the bioavailability of free estradiol and testosterone, through hyperinsulinemia, elevated IGF-1 bioavailability, and decreased hepatic secretion of SHBG. This evidence concerns the gene CYP19A1 and hyperinsulinism.