How is biosynthesis of estrogen compartmentalized and regulated within the cell?

 

Estrogen biosynthesis involves two cells, theca and granulosa cells, in the ovarian follicle. It also occurs in luteal cells and to a small extent in leydig and Sertoli cells of the testis. In the ovary, androstenedione biosynthesis is regulated by LH at several points: LH increases expression of StAR, P450scc, 3 beta HSD and P450c17.

In the follicle, androstenedione diffuses out of the SER of the theca cells across the basement membrane of the follicle and into the SER of the granulosa cell, where it is aromatized the by P450 aromatase to estrone. FSH increases expression of P450 aromatase in granulosa cells. Estrone is converted to estradiol, which is approximately 10 times as potent as estrone by 17 beta HSD.