Sex Hormone

sex hormone [′seks ‚hȯr‚mōn]

(biochemistry)

Any hormone secreted by a gonad, but also found in other tissues.

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Sex Hormone 

a steroid hormone produced in the gonads that regulates sexual differentiation and sexual reproduction in vertebrates, including man. In mammals, although sex itself is determined genetically, sexual differentiation and sexual reproduction are regulated by a complex and interrelated system that embraces not only the sex hormones but other hormones as well, including the gonadotropic hormones (the luteinizing hormone [LH], the follicle-stimulating hormone [FSH], and prolactin) and the adrenocorticotropic hormone (ACTH) produced in the hypophysis, the chorionic gonadotropic hormone produced by the placenta, and the prostaglandins produced primarily in the tissues of the reproductive organs but also in other tissues.

The male sex hormones, or androgens, are produced in the interstitial tissue of the testes; the main hormone produced is testosterone. The female sex hormones are synthesized in the ovaries and are divided into estrogens, which are produced in the cells of maturing follicles (the main estrogen is estradiol) and gestagens and progestins, which are produced in cells of the corpus luteum (the main gestagen is progesterone).

Some sex hormones are synthesized in the adrenal cortex. In pregnant women they are also synthesized in the placenta. Estrogens are also produced in males, and androgens in females. The differentiation of sex characters in each sex depends primarily on the correlation between the different sex hormones present. Steroid sex hormones are biosynthesized primarily of cholesterol. This process is blocked in insects because of their inability to synthesize cholesterol. The stages of the biosynthesis of sex hormones in the testes and ovaries coincide until progesterone is formed. The biosynthesis of steroid sex hormones is regulated by hypophyseal LH and FSH. Once produced, the sex hormones in turn act on the hypophyseoportal system and influence the secretion of LH and FSH (the feedback principle). The onset of sexual maturity is reflected in the intensified biosynthesis of sex hormones in the gonads, which is apparently induced by the rise of the hypothalamic sensitivity threshold to the sex hormones. The result is a sharp increase in the production of specific peptides in the hypothalamus that stimulate the hypophysis to secrete LH and FSH.

Sex hormones in adults regulate the reproductive function. Steroid sex hormones control the development of secondary sex characteristics and stabilize sexual desire. The interaction of estrogens and gestagens prepares the uterus for the implantation of the fertilized ovum and then ensures pregnancy and childbirth at term. The secretion of androgens in adult males is uniform, while the secretion of estrogens and gestagens in females varies throughout the sex and reproductive cyles. The biosynthesis of female sex hormones increases sharply during pregnancy, when they are also produced in the placenta. The action of the sex hormones consists in the biochemical mechanism of bonding to specific receptors in dependent tissue cells and subsequent stimulation of the biosynthesis of corresponding enzymes.

In addition to the reproductive system, other systems of the body are also greatly influenced by sex hormones. Medically, sex hormones are used in the substitution therapy of endocrine diseases, in the treatment of obstetrical and gynecological diseases, and in the treatment of neoplasia of the prostate and mammary glands (as antineoplastic agents). Sex hormones that have been chemically modified so as to selectively intensify the desired physiological action are often used.

Substances analogous to sex hormones exist even in the simplest organisms. There is evidence that sexual reproduction is regulated by hormones in some ascomycetes and phycomycetes and in other fungi. In the water mold Achlya bisexualis, the male and female varieties of sexual cells of the hyphae secrete substances that mutually stimulate the formation and coalescence of these cells. Trisporic acids related to the carotenoids perform a similar function in a number of microorganisms, such as Blakeslea trispora and some species of Mucor and Rhizopus. The substances secreted in the cells of one sex reach the cells of the other sex through the surrounding medium. The greater the spatial separation between male and female gametes, the more the action of these regulators resembles the action of sex pheronomes and not sex hormones.

REFERENCES

Grollman, A. Klinicheskaia endokrinologiia i ee fiziologicheskie osnovy. Moscow, 1969. (Translated from English.)
Eskin, I. A. Osnovy fiziologii endokrinnykh zhelez. Moscow, 1968.1
Rukovodstvo po endokrinologii. Moscow, 1973.
Clegg, P., and A. Clegg. Gormony, kletki, organizm. Moscow, 1971. (Translated from English.)
Biochemical Actions of Hormones, vol. 2. Edited by G. Litwack. New York-London, 1972.
Hormones in Blood, 2nd ed., vol. 2. Edited by C. H. Gray and A. L. Bacharach. London-New York, 1967.
Barksdale, A. W. “Sexual Hormones of Achlya and Other Fungi.” Science, 1969, vol. 166, no. 3907, p. 831.

B. V. POKROVSKH and E. P. SEREBRIAKOV