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Hormone
A hormone is a
chemical substance produced by an endocrine gland that has a specific
effect on the activities of other organs in the body. Sex hormones are
substances secreted by the sex glands (ovaries and testicles) and the
adrenal gland directly into the bloodstream. They are partially
responsible for determining the sex of a fetus and for the proper
development of sex organs. They also initiate puberty and later play a
role in the regulation of sexual behavior.
The major sex hormones
can be classified as estrogens or androgens. Both classes of hormones
are present in males and females alike, but in vastly different amounts.
Most men produce 6-8 mg of testosterone (an androgen) per day, compared
to most women who produce 0.5mg daily. Estrogens are also present in
both sexes, but in larger amounts for women.
Estrogens are the sex
hormones produced primarily by a female's ovaries that stimulate the
growth of a girl's sex organs, as well as her breasts and pubic hair,
known as secondary sex characteristics. Estrogens also regulate the
functioning of the menstrual cycle. In the majority of women, ovarian
hormones appear not to play a significant role in their sex drive. In
one study of women under the age of 40, 90 percent reported experiencing
no change in sexual desire or functioning after sex hormone production
was shut down because of the removal of both ovaries. Estrogens are
important in maintaining the condition of the vaginal lining and its
elasticity, and in producing vaginal lubrication. They also help
preserve the texture and function of a woman's breasts. In men,
estrogens have no known function. An unusually high level, however, may
reduce sexual appetite, cause erectile difficulties, produce some breast
enlargement, and result in the loss of body hair in some men.
Androgens are sex
hormones produced primarily by a male's testes, but are also produced in
small amounts by the female's ovaries and the adrenal gland, an organ
found in both sexes. Androgens help trigger the development of the
testes and penis in the male fetus. They jump start the process of
puberty and influence the development of facial, body and pubic hair,
deepening of the voice, and muscle development, the male secondary sex
characteristics. After puberty, androgens, specifically testosterone,
play a role in the regulation of the sex drive. Large deficiencies of
testosterone may cause a drop in sexual desire, and excessive
testosterone may heighten sexual interest in both sexes. However,
testosterone levels are poorly correlated with sexual interest and drive
when they are within the average range. Sex drive is much more likely to
be affected by external stimuli (sights, sound, touch) than by
variations in sex hormones, except in extreme cases. In men, too little
testosterone may cause difficulty obtaining or maintaining erections,
but it is not clear whether testosterone deficiencies interfere with
female sexual functioning apart from reducing desire.
However, there is no
evidence whatsoever to suggest that because women have less testosterone
than men do, they have lower sexual interest than their male
counterparts. Instead, it seems that women detect and react to much
smaller amounts of testosterone in their circulation than men do.
Aging, illness and
certain cancer treatments can affect our bodies' delicate hormonal
balance, causing changes in sexual interest and functioning. Familiar to
most are the changes that occur when a woman goes through menopause.
Estrogen production drops throughout this process as a woman exits her
child-bearing years. The major sexual impact of decreased estrogen is a
shrinking of the vagina and thinning of the vaginal walls, along with a
loss of elasticity and decreased vaginal lubrication during sexual
arousal. Some women experience only slight changes in sexual
functioning, while others have dryness and pain with intercourse, or
genital soreness for a few days after sexual activity, if they don't use
a vaginal lubricant or take some form of hormone replacement.
Researchers investigating
the effects of hormone replacement therapy on women's sexual functioning
have shown that taking estrogen often allows sexual functioning to
return to normal. In addition, androgens have been prescribed for
postmenopausal women to enhance their sexual desire.
Perhaps less well known
is the fact that men sometimes experience lowered testosterone levels,
which can be responsible for sexual dysfunction. How this hormonal
decrease affects the man's sex drive and erections remains unclear. But
urologists, as a treatment for these difficulties, sometimes recommend
testosterone replacement. There is a great deal yet to be learned about
which men and women may require and benefit from hormone replacement
therapy.
It is tempting to try to
understand sexual behavior solely in terms of hormones. In many animal
species hormones that control the female's willingness to mate and the
courtship and sexual behavior of the male tightly regulate patterns of
sexual behavior. In humans, however, there is a more complicated
relationship between hormones and sexual behavior. Although a
substantial testosterone deficiency usually reduces sexual interest in
men and women, there are cases in which that effect is not seen.
Similarly, although many men with below normal testosterone levels have
difficulty with erections, not all do. Women who have low amounts of
estrogen in their bodies do not lose their ability to be sexually
aroused or to have orgasms. In short, sex hormones are not the only
factors affecting sexual interest or behavior. If you are concerned
about your hormone levels and whether they may be effecting your general
health or your sexual functioning, consult your doctor for some easily
performed and (almost) painless laboratory blood work.
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Sex
