Developing reproductive system

Research evidence indicates that nonylphenol or octylphenol can adversely affect the functioning of various organ systems, the developing reproductive system, immune function, neurological function and behavior, and obesity and diabetes risk. 

Exposure to excessive amounts of lead over a long period of time (chronic exposure) increases the risk of developing certain diseases. The parts of the body which may be affected include the blood, nervous system, digestive system, reproductive system, and kidneys. These effects include anemia, muscular weakness, kidney damage, and reproductive effects, such as reduced fertiHty in both men and women, and damage to the fetus of exposed pregnant women. 

In order to fully appreciate the potential implications of endocrine disruption, it is important to consider the normal role of hormones in controlling the development and functioning of the reproductive systems of the different vertebrate classes. 

Effects of Oestrogen on the Development and Function of the Male Reproductive System... 

Recently, leaders in the pharmaceutical industry have developed a list of desired properties for a fourth generation of SERMs (Table 2). In general, future SERMs must oppose endogenous hormone action in the breast and reproductive system while displaying full estrogenic effects in the cardiovasculature, bone and central nervous systems. Additional criteria are that fourth generation compounds possess superior bioavailability compared with existing SERMs and have... 

The estrogens are secreted by the ovarian follicle and in smaller amounts by the adrenal cortex. Estrogens are important in the development and maintenance of the female reproductive system and the primary and secondary sex characteristics. At puberty, they promote growth and development of the vagina, uterus, fallopian tubes, and breasts. They also affect the release of pituitary gonadotropins (see Chap. 50). 

In some animals, consumption of a phytoestrogen-rich diet can cause temporary infertility and reproductive system disorders (Irvine, 1999). In humans, lower testosterone levels and a decline in human semen quality over the past century have been luiked to increased exposure to environmental endocrine disrupters (EDCs) (Sharpe and Skakkebaek, 1993). Furthermore, cases of sexual impotence have been reported in males exposed to synthetic estrogens in the pharmaceutical industry (Mattison et al., 1990). If this might be the case, the fetal-prepubertal period and Sertoli cell development would be of critical importance (Sharpe and Skakkebaek, 1993). However, an adverse effect of phytoestrogens on male fertility has yet to be proven. Recent work (Mitchell et al., 2001) addressing this point led to the conclusion that up to 40 mg/day of isoflavones over a two-month period had no effects on gonadotrophin and... 

This mode of regulation seems appropriate to the ERTs since their cells are already terminally differentiated, and their primary function is to grow and provide a nutrient rich incubator for the undifferentiated neuroblasts and imaginal cells that eventually produce the reproductive adult. The response of these undifferentiated progenitor cells to food withdrawal is quite unlike that of the ERTs. Larval neuroblasts and imaginal disc cells continue to proliferate for many days after a larva is starved, and seem to complete their normal proliferation programs. In this instance the ERTs lose mass, presumably as they transfer stored nutrients to the developing nervous system and the discs. 

In permissiveness, one hormone enhances the responsiveness of the target tissue to a second hormone in other words, the first hormone increases the activity of the second. For example, the normal maturation of the reproductive system requires reproductive hormones from the hypothalamus, pituitary, and gonads as well as the presence of thyroid hormone. Although thyroid hormone by itself has no effect on the reproductive system, if it is absent the development of this system is delayed. Therefore, thyroid hormone is considered to have a permissive effect on the reproductive hormones, facilitating their actions causing sexual maturation. 

Makeyeva, A.P., N.G. Yemel yanova, N.V. Belova, and I.N. Ryabov. 1995. Radiobiological analysis of silver carp, Hypophthalmichthys molitrix, from the cooling pond of the Chernobyl nuclear power plant since the time of the accident. 2. Development of the reproductive system in the first generation of offspring. Jour. Ichthyol. 35 40-64. 

The reproductive system includes the ovaries in the female and testes in the male, together with the ducts and tubes in which the ovum or spermatozoa travel and meet in the fallopian tube, and the environment in which the foetus develops. Since both ovary and testis produce hormones, there is overlap with the endocrine system (Chapters 12 and 19). 

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