progesterone -»-17a OH-progesterone--androstenedione
17a-hydroxylase 17,20 lyase
FIGURE 58-1 Pathway of synthesis of testosterone in the Leydig cells of the testes. Leydig cells express steroid 17a-hydroxylase (CYP17), which carries out sequential 17-hydroxylation and C17-20 lyase reactions in the biosynthetic pathway to produce androgens. Bold arrows indicate favored pathways.
effects that occur via the androgen receptor Testosterone and dihy-drotestosterone act as androgens via the AR. The AR is a member of the nuclear receptor super-family that contains amino-terminal, DNA-binding, and ligand-binding domains. After testosterone and dihydrotestosterone bind to the ligand-binding domain, they cause a conformational change that allows the ligand-AR complex to translocate to the nucleus, bind via the DNA-binding domain to androgen response elements on certain responsive genes, and regulate their transcription. One i,
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