 Expression of CYP17A1 has been found in all of the traditional steroidogenic tissues except the placenta, including the zona reticularis and zona fasciculata of the adrenal cortex, the Leydig cells of the testes, the thecal cells of the ovaries, and, more recently, in luteinized granulosa cells in ovarian follicles.In addition to classical steroidogenic tissue, CYP17A1 has also been detected in the heart, kidney, and adipose tissue.In the fetus, CYP17A1 has been reported in the kidney, thymus, and spleen.