Androstenedione, formed in thecal cells under the stimulatory effects of LH, diffuses across the basement membrane where, under the action of FSH, it is converted to estradiol. In the developing follicle LH receptors (LH-R) are only located on the thecal cells and FSH receptors (FSHR) on the granulosa cells. The ‘dominant’ pre-ovulatory follicle develops LH-Rs on the granulosa cells prior to the LH surge. Thecal cells of the preovulatory follicle also develop the capacity to synthesize estradiol (dotted lines) and this persists when the thecal cells become incorporated into the corpus luteum.
*Aromatase; +, 17β-hydroxysteroid dehydrogenase
From: Chapter 6, The gonad
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