Figure 7.

Granulosa and theca cells cooperate to produce steroid hormones. Before the LH surge, (i) theca cells produce predominantly androgens in response to LH, (ii) androgens diffuse to granulosa cells, and (iii) granulosa cells convert androgens to estrogens in response to FSH. After the LH surge, (i) decreased CYP17A1 expression increases progesterone synthesis and decreases androgen synthesis in theca cells, and (ii) increased HSD3B1 increases progesterone synthesis and declining CYP19A1 decreases estrogen synthesis by granulosa cells. The LH surge also increases HSD11B1 and decreases HSD11B2 in granulosa cells to increases synthesis of cortisol from circulating cortisone. Enzymes shown in green increase after the LH surge. Enzymes shown in red decrease after the LH surge.