Reproductive organs, hormonal control

Reproductive organs are the primary source of the steroid hormones that influence sexual and reproductive functions. In men, the testes produce testosterone and similar androgens that are responsible for spermatogenesis and the secondary sexual characteristics of adult males.7,26 In women, sexual maturation and reproductive function are governed by the production of estrogens and progestins from the ovaries.27 The release of male and female sex steroids is controlled by hormones from the hypothalamus and anterior pituitary.32 The control of male and female hormone activity and the pharmacologic implications of these hormones are discussed in Chapter 30. 

Endocrine and Reproductive Effects. Because the male and female reproductive organs are under complex neuroendocrine and hormonal control, any toxicant that alters any of these processes can affect the reproductive system (see Chapters 17 and 20). In addition metals can act directly on the sex organs. Cadmium is known to produce testicular injury after acute exposure, and lead accumulation in the testes is associated with testicular degeneration, inhibition of spermatogenesis, and Leydig-cell atrophy. 

Hasegawa, R., and Eisenberg, E, Jr., 1981, Selective hormonal control of myo-inositol biosynthesis in reproductive organs and liver of the male rat. Proc. Natl. Acad. Sci. U.S.A. 78 4863-4866. 

Two groups of hormones regulate development and reproduction in insects, namely the ecdysteroids and the JHs. In crustaceans too, ecdysteroids are involved in the hormonal control of growth, and a chemical compound, which is similar to the JHs of insects, is present and thought to play a role in crustacean reproduction and development. The insect JH is a species-specific acyclic sesquiterpenoid epoxide, which is synthesized in a pair of retrocerebral epithelial organs called the corpora allata (CA see Fig. 1). In decapod crustaceans, MF is the unepoxidated form of the insect JH III and it is synthesized and secreted from the MOs (see Section 3.2.4). 

Effects of thyroid hormone The organ level actions of the thyroid drugs include normal growth and development of the nervous, skeletal, and reproductive systems and control of metabolism of fats, carbohydrates, proteins, and vitamins. The results of excess thyroid activity (thyrotoxicosis) and hypothyroidism (myxedema) are summarized in Table 38-1. 

The review of the available data concerning the control of PG in reproductive organs suggests the existence of multiple hormonal and intracellular signaling systems regulating PG production. It includes classical hormones (LH, GH, OT,... 

Of the sex hormones, the most important male hormone is testosterone (Figure 21.25d), a hormone that controls the growth of the reproductive organs and hair and the development of the muscle structure and deep voice that are characteristic of males. There are two types of female sex hormones of particular significance progesterone (Figure 21.25e) and a group of... 

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