Roles of Estrogen in Development - Essay Example

Most species with two sexes exhibit sexually dimorphic behavior and physical characteristics. New research suggests that the presence of estrogen, specifically estradiol, has an active role in sexual differentiation. Several sexual dimorphic structures in the brain have been observed in laboratory experiments. This study had been performed using male and female rats and had proved the differences in size of corpus callosum between two sexes had existed facilitated by estrogen. Estrogen plays an important role in male reproduction, critical for sustained fertility in some species.

Reducing estrogen's interaction with its receptor(s) in monkey and mouse models is associated with reduced sperm motility and, in some cases, documented elimination of sperm fertilizing ability, suggesting that normal epididymal function may be estrogen dependent. The objective of the experiments was to evaluate the effects of reduced endogenous estrogen on development of epididymal function in the pig, a species in which males have very high levels of endogenous estrogen. Furthermore, reducing endogenous estrogen during postnatal development appears to have transient effects on porcine epididymal function.

These transient effects suggest that the pig, with its high endogenous estrogen, may respond differently than other species to reduced estrogen synthesis (McCarthy, et al). This particular study provides a viable claim of estrogens importance on development of reproductive system particularly in male specie. The development of the positive feedback of estrogen in normally fed animals and its possible alterations in animals subjected to restricted food intake has been the focus of another study and had indicated that the gonadotropin response to estrogen positive feedback develops gradually and quantitatively as the animal matures and undernutrition-induced delayed puberty is not caused by inability of the hypothalamic-pituitary unit to respond to positive estrogen feedback, but rather to ovarian failure to release estrogen in amounts sufficient to trigger a gonadotropin surge (Ronnekleiv, et al).

Another study had determined whether endogenous estrogen, the levels of which increase with advancing pregnancy, regulates growth and development of the baboon fetal adrenal cortex. In the end it propose that estrogen acts directly on the fetal adrenal cortex to selectively repress the morphological and functional development of the fetal zone, potentially as a feedback system to maintain physiological secretion of estrogen precursors and thus placental estrogen production to promote normal primate fetal and placental development (Albretch, et al).

Despite the estrogens' significance on development, some studies apparently speak of its contribution to developmental errors. Evidences have accumulated that exposure to environmental components with estrogenic activity causes reproductive disorders in human populations. Studies conducted over the past 50 years have clearly shown a continual decline in semen quality accompanied by an increase in male reproductive disorders during this period in industrial countries. As healthy gametes are a prerequisite for healthy children, such disorders are a significant problem not only for the current society, but also for future generations.

Epidemiological, clinical, and experimental studies have suggested that excessive exposure to estrogens and xenoestrogens during fetal and neonatal