| The conversion of corticosteroids into androgens requires the 17-20 lyase/desmolase enzyme and a substrate that contains a 17α-hydroxyl group. This stimulates the addition of a 17α-hydroxyl group prior to breaking the C-17-C-20 bond to yield the androstane ring structure. This enzyme is abundant in the Leydig cells of the testis and in the granulosa cells of the ovary. In these cases, however, the stimuli to the rate-limiting cholesterol side-chain cleavage step are luteinizing hormone (LH) and follicle-stimulating hormone (FSH), respectively. Thus the same biosynthetic step, is controlled by two different hormones in two different tissues.
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