BPA likely targets and down-regulates the expression of cytochrome P450 side-chain cleavage (Cyp11a1). CYP11A1 is tethered to the inner mitochondria membrane and works in conjunction with steroidogenic acute regulatory protein (STAR), tethered to the outer mitochondrial membrane. STAR transports cholesterol from the cytoplasm to the inner mitochondrial member where CYP11A1 removes the side-chain of cholesterol, synthesizing pregnenolone. Pregnenolone is the hormonal precursor required for synthesis of hormones with the estradiol biosynthesis pathway, including progesterone, dehydroepiandrosterone (DHEA), androstenedione, testosterone, estrone, and estradiol. Disruption of pregnenolone metabolism would negatively impact hormone production in antral follicles. Thus, BPA likely decreases the expression of Cyp11a1, leading to a decrease in hormones within the estradiol biosynthesis pathway due to a lack of pregnenolone.