Cholesterol is also converted to sex hormones by the way of Δ⁵-pregnenolone. Progesterone can be formed and further converted to testosterone. Progesterone can enter an alternate pathway to form dehydroxyepiandrosterone. This compound can be converted to 17-β estradiol action of 17-reductase. Also, estradiol can be formed from testosterone by the action of the aromatase system. Steroid hormones are generally converted into metabolic excretion production in the liver. Approximately, 20% to 30% of these metabolites are secreted into the bile and then excreted in the faeces, whereas the remainder are released into the blood and are filtered from the plasma in the kidney, passing into urine.