Development of the reproductive system, which comprises the gonads and external genitals in male and female embryos and fetuses, is under very complex and exquisitely synchronized genetic and hormonal control. The reproductive system is unique among the functional organ systems in the body in that it has the most pronounced sexual dimorphism. The gonads can develop either into a testis or an ovary, which differ markedly from each other in several aspects of the biology of gamete production. On the other hand, the accessory reproductive organs in the female are mainly geared for future implantations and gestations, while the male function is limited to the delivery of spermatozoa. During the last decades, a number of genes responsible for primary sex differentiation have been discovered, as well as endocrine and paracrine signaling pathways regulating these events and the subsequent development of gonads, ducts, and external genitalia. Many of the breakthroughs in our understanding of this system were made in observing abnormal development of the reproductive system in humans or in animal models with targeted gene disruption. Despite these advances, a great deal remains to be elucidated. While certain gene pathways leading to reproductive abnormalities have been relatively well described, little is known about the role of environmental and lifestyle factors, especially in mild cases. A possible relationship between prenatal exposures to environmental endocrine disrupters and abnormalities of the reproductive system, including genital malformations, testicular germ cell tumors, and some forms of infertility in adult life has been proposed (Toppari et al. 1996; Skakkebaek et al. 2001).
KeywordsGerm Cell Leydig Cell Congenital Adrenal Hyperplasia External Genitalia Gonadal Dysgenesis
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