Intragonadal regulation of male and female reproduction

FSH and LH are vital endocrine regulators of gonadal growth and function. However, locally produced--paracrine--steroidal and nonsteroidal substances mediate and modulate gonadotrophin action on gonadal cells. The testis and ovary share obvious morphological and functional homologies. Optimal functioning of the spermatogenic (Sertoli cells) and follicular (granulosa cells) epithelia depends on both endocrine stimulation by FSH and paracrine stimulation by androgen. In each gland, inhibins and related factors produced by FSH-stimulated Sertoli (testis) cells or granulosa (ovary) cells reciprocally modulate LH-stimulated androgen synthesis in neighbouring Leydig (testis) or thecal (ovary) cells. Thus androgens and inhibins are "unisex" paracrine regulators that operate in similar ways in both ovary and testis.