Concentration–response curves of compounds that increase or decrease levels of steroid hormones in the culture medium. The dotted line shows the 0.667- and 1.5-fold change in steroid hormone level compared with the vehicle-treated control, which is used to calculate the EC_IR1.5. The y axis in the graphs on progesterone and 17a-OH-progesterone is in logarithmic scale to keep the 1.5-fold change discernable while showing the large fold changes induced by some compounds at the highest tested concentrations. DHEA, dehydroepiandrosterone; E1, estrone; E2, estradiol.