The Role of Hormones


The proper anatomical development of males and females as well as their ability to reproduce depend on the functioning of special glands in their bodies. The scientific study of these glands and their secretions is still in progress and much remains to be learned about them.

People have, of course, long been familiar with some of the more complex glands (such as those in the mouth, skin, or female breast) which release their particular secretions (saliva, sweat, milk) onto a surface through their own ducts. Such secretions are easily detected, traced, and measured, and they serve an obvious localized function. However, the human body also possesses ductless glands which release their secretions directly into the bloodstream. These glands are called endocrine (Greek: internally secreting) glands. Their secretions, which may stimulate or regulate the functioning of various other, often remote organs, are known as hormones (from the Creek hormaein: to arouse). Every human body contains a number of endocrine glands and many different hormones which serve a great variety of purposes. The following paragraphs restrict themselves to a discussion of those hormones that affect a person's sexual and reproductive capacities.

In regard to sex and reproduction, the most important endocrine glands are the pituitary gland and the male and female gonads or sex glands. The pituitary gland is located at the base of the brain. It is sometimes called the "master gland" because its hormones stimulate and coordinate the other endocrine glands. Among the pituitary hormones that are of particular interest here are FSH (follicle-stimulating hormone) and LH (luteinizing hormone). They stimulate the male and female gonads to produce hormones of their own (In males, LH is usually referred to as ICSH [interstitial-cell-stimulating hormone] because it acts upon the interstitial cells, the producers of hormone in the testicles.

The gonads or sex glands are the testicles in the male and the ovaries in the female. (See "The Male Sex Organs" and "The Female Sex Organs") The hormones produced by the gonads are called gonadal hormones, and they can be divided into clearly distinct groups. One group of hormones that are particularly prominent in mature males are known as androgens. Another group of hormones particularly prominent in mature females are known as estrogens. (The female gonads also produce still another hormone called progesterone, which is important for a woman's reproductive life.) However, while there is a preponderance of androgens in men and of estrogens in women, both groups of hormones are present in every individual. The gonadal hormones play an important role in a person's sexual maturation. Their first decisive influence appears even before birth.

The human embryo is sexually undifferentiated during the first few weeks of its life. The primitive beginnings of its gonads are the same for both sexes. At the spot where the future external sex organs are destined to grow, there is a hump (suggestive of the male) and a groove (suggestive of the female). A clear differentiation begins only toward the end of the second month after conception. In the case of a male embryo, the production of the hormone testosterone (one of the androgens) is started, which slowly transforms the embryonic genital hump into a penis. The groove running down its underside closes, forming a single internal tube: the urethra. The gonads become identifiable as testicles, and, in the last weeks before birth, they descend into the scrotum. Without this prenatal production of testosterone in males, their proper anatomical development is impossible.

In the case of a female embryo, nothing special or additional is needed because the external and internal sex organs differentiate "automatically." (In a sense, therefore, the female sex might be called the "basic" or "primary" one.) In the absence of a specific stimulation by androgens, the originally undifferentiated gonads are transformed into ovaries. The embryonic genital hump grows into the clitoris. (Compared to the penis, the clitoris remains much smaller because of a lack of testosterone to stimulate its growth.) The genital groove, on the other hand, remains open and deepens, forming the minor lips and the vestibule of the vulva.

In the period between birth and puberty, there are no further dramatic changes in a person's sexual development. The levels of androgen and estrogen remain rather low and are nearly equal in both sexes. At about the age of eight, a gradual buildup of hormone levels begins. By about ten or eleven, this increase becomes very substantial, especially in females. The pituitary gland releases great quantities of FSH and LH (called ICSH in males) which stimulate the secretion of gonadal hormones as well as the production of sperm in the testicles and of eggs in the ovaries. In males, the androgens rise to a slightly higher level than the estrogens, and, in females, the estrogens rise to a much higher level than the androgens. As a result of this intensified hormonal bombardment, the male and female bodies develop their secondary sexual characteristics. This general physical maturation also fully develops the capacities of the nervous system, and thus creates the basis for the complete male and female sexual response.

In those rare cases where boys or girls lose or fail to develop their gonads, their overall physical development is affected. Their ability to respond sexually remains limited and, of course, the secondary sexual characteristics never become pronounced. For example, a boy whose testicles fail to descend or who is castrated before puberty retains a rather juvenile general appearance and never experiences the typically male enlargement of the larynx and the resulting voice change. In 18th-century Europe music lovers took advantage of this fact when they provided the opera stage with a very special type of human voice—that of the castrate. A great number of young boys with promising voices were castrated in order to preserve their tonal clarity and high pitch. At the same time they received a rigorous musical training. Eventually some of them developed into adult male sopranos or contraltos of incomparable vocal force and virtuosity who could look forward to a life of fame and fortune. The greatest composers, such as Handel, Gluck, and Mozart, wrote major parts in their operas for castrated males. Since today this type of voice is no longer available, these operas have to be rearranged for modern voices, or they are simply no longer performed.

The castration of adults does not have the same obvious result as that of children. This has long been known in many Asian and Middle Eastern countries where, in the past, adult male slaves or servants were castrated for the sake of obtaining harem guards who would be unable to impregnate their master's wives. (Actually, a sterilization would have been sufficient for this purpose.) Apart from their infertility these so-called eunuchs did not necessarily show any other physical deficiencies. The modern stereotype of the eunuch as a falsetto-voiced, bald, fat weakling is false. Again, the public of 18th-century Europe seems to have had a remarkable and very realistic appreciation of the biological facts. For example, in Mozart's popular opera, The Abduction from the Seraglio, the part of the harem guard is, quite appropriately, written for a deep bass voice (moreover, he is portrayed as quite lecherous). As a rule the adult human body is capable of adjusting to a lack of gonadal hormones within a few months, although in some instances there may be some premature physical deterioration over the years. In any case today the effects of castration, such as they are, can be almost completely corrected by hormonal treatment.

As mentioned earlier, the scientific study of hormones continues as many important questions about their effects are still unanswered. Nevertheless there is now some general, if vague, knowledge of these problems among the public at large. Indeed, many men and women today discuss hormonal influences as readily and casually as their diets. Unfortunately many popular notions about the role of hormones are quite mistaken, especially in regard to sex.

Part of the confusion can be explained by the history of endocrinology (the study of endocrine glands and their secretions). Among the first hormones to be discovered were those secreted by the gonads or sex glands. Since the gonads were known to produce male and female gametes or sex cells, the gonadal hormones were soon simply referred to as sex hormones, and they were also divided into male and female sex hormones. However, this all too convenient analogy is faulty. While the male sex cells (sperm) are produced only in the male (and are therefore properly named), the so-called male sex hormones (androgens) are produced in both males and females. Correspondingly, the female sex cell (egg) is produced only in females (and is therefore properly named), whereas the so-called female sex hormones (estrogens) are produced in both sexes. The distinction between "male" and "female" sex hormones is therefore misleading. In fact, it is regrettable that the gonadal hormones were ever called "sex hormones" in the first place, because this term has led to the misconception that they somehow determine sexual behavior. For example, some people believe that the sex hormones are the direct cause of sexual desire, and that an increase in these hormones will increase the desire just as effectively as their reduction will reduce it. Indeed, there is a widely held false opinion that one can prevent a man from engaging in any sexual activity at all by depriving him of his sex glands and thus his "sex hormones." In some countries sex offenders are being castrated under the assumption that this will put an end to their offensive behavior. However, modern scientific studies clearly show that, for a grown man, the removal or loss of the testicles may have little or no immediate effect on his sexual capacities. (Except, of course, that he becomes infertile. The same is true for a woman whose ovaries become inactive after menopause. Her sexual responsiveness remains undiminished.) Still, the indignity of a forced castration may cause severe psychological damage to someone who shares the common sexual superstitions. In this indirect way his sexual abilities may very well become impaired. The lack of androgens alone does not necessarily diminish sexual interest or inhibit sexual expression. It often decreases the level of sexual performance somewhat, but drastic changes may not become obvious until many years later.

Among the general public it is still not always understood that, in human beings, the ability to reproduce and the ability to respond sexually are two different matters. While the sex glands are indispensable for a young person's physical maturation and human reproduction, they are not essential for the sexual responsiveness of adults. In other words, there can be no reproduction without sex cells (sperm and egg), but there can very well be sexual activity without "sex hormones" (androgens and estrogens).


Money, John, and Ehrhardt, Anke A. Man & Woman, Boy & Girl: Differentiation & Dimorphism of Gender Identity. Baltimore and London: Johns Hopkins University Press, 1973 (cloth); 1976 (paper).

Money, John, and Tucker, Patricia, Sexual Signatures: On Being a Man or a Woman. Boston: Little, Brown & Company, 1975 (cloth); 1976 (paper).


[Title Page] [Contents] [Preface] [Introduction] [The Human Body] [Sexual Differentiation] [The Sex Organs] [Sexual Response] [Human Reproduction] [Physical Problems] [Sexual Behavior] [Sex and Society] [Epilogue] [Sexual Slang Glossary] [Sex Education Test] [Picture Credits]