Hormones and Other Sex Chemicals

The human body produces a variety of chemicals to carry out its living functions. Chief among these are what are known as hormones. Hormones are chemicals produced by endocrine glands, and affect specific functions of other organs.

They are used to regulate and stimulate a variety of bodily processes, including those associated with sexuality and reproduction.

There are a variety of hormones that you will hear and see discussed relative to sexual functioning and concepts related to sex, such as pregnancy. It is important to understand what these are and how they work to effect changes upon the body.

This article is intended as a brief overview of the more important chemicals involved in sexuality, not an in-depth analysis of them. The reader is encouraged to seek out more detailed sources of information if desired.


Testosterone is perhaps the most familiar hormone, and is from a family of hormones called androgens. Best known for their "masculine" effects, androgens first kick into action during the embryonic stages of life. When an embryo is conceived (a female egg is fertilized with a male sperm), the egg and sperm each donate a single sex chromosome to the embryo - an X chromosome from the female, and an X or Y chromosome from the male.

The embryo will be female if the combination of sex chromosomes is XX, and male if the combination is XY. It is not until the sixth week of development that XX or XY embryos are anatomically defined, and before this the fetus is essentially genderless, possessing a set of "indifferent" genitalia. One interpretation of this is that all embryos begin as female. Testosterone makes the difference, influencing the growth of male genitalia. As the child develops, especially throughout puberty and into young adulthood, testosterone causes muscle buildup, thickening of the vocal cords (causing the voice to deepen), causes elongation and widening of the penis, and the development of body hair among other attributes. (1)

Despite testosterone's frequent association with males, females produce it as well, although males produce approximately 20 times more than females. In males, the testes produce it, while in females, it is produced in the ovaries (the ovaries are analogous to the male testicles). In addition to the functions outlined above, it also helps support energy levels, immune functions, and works to protect the body against osteoporosis.

Testosterone is also the chief driver of the libido in both males and females. If testosterone levels are too low in either sex, a reduction in sexual appetite is not uncommon. Males may have trouble maintaining an erection or even lose the desire for sex altogether. In some cases, as a result of birth control use by females suppressing the release of testosterone (as the precursor of estrogen, see below), the sex drive of the female may also be somewhat inhibited.

The human body synthesizes estrogen from its supply of testosterone. It is this fact (among others) that has led to the recent realization that there are not necessarily two diametrically opposite genders. If the body produces shifting amounts of testosterone, and synthesizes varying amounts of estrogens from that quantity of testosterone, it would seem reasonable that many gender traits could exist along a continuum not unlike that identified for sexuality (Kinsey, et. al.). Significant research is being conducted along these lines today with the hopes of a better understanding of the role this hormone plays in determining things like gender, sexual orientation, etc.


Estrogen is actually a group of hormones rather than a specific one and, although they are present in both sexes, they are present in much higher levels in females of reproductive age. The most important estrogen, Estradiol, is in fact produced from testosterone (as described above). Like testosterone in the males, estrogens are responsible for the development and formation of the secondary sexual characteristics of the maturing female body. This includes things such as uterine growth, breast enlargement and functionality, and maintenance of vaginal elasticity and lubrication. The hormone has no known effect in men, though if present in elevated quantities, signs such as breast development may be seen.

Estrogen also works to stimulate the production of Follicle Stimulating Hormone (FSH), or the hormone responsible for the onset of the ovulation cycle each month. Combination birth control pills (see below) work in preventing pregnancy by artificially maintaining a higher than normal level of estrogens in the body, thereby preventing ovulation. Estrogens are present in high levels during pregnancy, so the body believes it is pregnant and therefore does not release another egg.


Progesterone is a hormone involved in the female menstrual cycle, and is produced in larger quantities during pregnancy. It suppresses ovulation, prepares the inner lining of the uterus for implantation, and functions to reduce the female's immune system sensitivity to allow the body to accept the developing fetus without attacking it. Progesterone has many other functions outside those associated with reproduction. It works as an anti-inflammatory agent, regulates immune response, and regulates the body's use of fat stores as energy. The male also has this hormone in his body, but in levels similar to that in pre-ovulation in females.

Progestin is a synthetic version of progesterone, and is what is commonly found in both the combination birth control pill and the "mini-pill." A synthetic version is required because the natural version was not easily absorbed when taken orally, thereby reducing its effectiveness as a contraceptive agent. The progestin in this works to keep the hormone levels artificially inflated such that, as with estrogen, the body thinks it is pregnant. The elevated progestin levels also keep the cervical mucus thickened, inhibiting the entrance of sperm into the uterus, and thins the endometrium (the inner wall of the uterus), which may inhibit implantation of an egg (though this has not been confirmed in a laboratory setting). During the placebo pill cycle, the progestin level in the body drops, and menstruation occurs - the normal menstrual bleeding is the direct result of a drop in progestin levels.

Human Chorionic Gonadotropin

Human Chorionic Gonadotropin (HCG) is the hormone that exerts control over the progesterone if the female becomes pregnant. It works to maintain sufficient levels of progesterone to ensure the viability of the fetal environment in the uterus. This hormone is initially produced at implantation, and is the chemical for which pregnancy tests check in the blood or urine. The little blue stripe on an HPT strip indicates the presence of HCG, and since this hormone is only produced when pregnancy has begun, it is a reliable indicator that a female is pregnant.


Oxytocin is a hormone that is released during orgasm in both sexes, and is responsible for the bonding or emotional connection that occurs as the result of a sexual encounter. Oxytocin is released during breastfeeding, and is believed to be responsible for the pleasurable feelings and bonding that take place between mother and child during this period of development. The hormone is responsible for inducing labor, and is believed to facilitate sperm transport during ejaculation as well. Oxytocin increases the sensitivity of the penis, clitoris and nipples and improves the quality of erections in males. The most important role of oxytocin, however, may be in the relieving of stress, and this appears to be one reason why sex is such a great stress relieving activity.

Oxytocin is naturally released even when the skin is touched, and the warm and fuzzy feeling you get from a lover touching you leads to the desire to be touched more (this is also known as " skin hunger"). Its effectiveness as the "cuddle hormone" is driven by the presence of estrogen, and this may explain why women have a much greater need for intimacy than do men ( i.e., due to the higher levels of estrogen in the female body). As a result of oxytocin producing the desire to be touched, it creates its own wonderful feedback loop.


Pheromones, at their basic level, are chemicals produced by an organism that transmit some message to another member of the same species. The most common examples of these are the chemicals that allow males of some species to detect when a female is in oestrus (heat) and receptive to sex. There have been no conclusive scientific studies that have demonstrated that humans produce pheromones that affect sexual behavior in any way, despite claims of some manufacturers of substances that claim to have such an effect.

The Role of Hormones and Birth Control

There are two basic types of hormonal contraceptive devices. The "combination" device (usually a pill) contains a both estrogen and progestin, while the "mini" pill/device contains just progestin. The combination contraceptive works by keeping the estrogen and progestin levels elevated in the body to fool the body into thinking it is pregnant. Once you go from taking the regular pills to taking the placebos or sugar pills, the body goes into its menstrual cycle because of the reduction in estrogen and progestin. The same basic principle is at work with the progestin-only pills.

The key to maintaining the efficacy of these kinds of contraceptives, then, is ensuring that the chemical levels are maintained in the body. With the progestin-only pills, you have a window of about 3 hours before they begin to lose their efficacy; whereas with the combination pills, the window is roughly 12 hours. Emergency contraception works by flooding the body with a controlled overdose of estrogen and progestin, which immediately bumps up the levels of these hormones to bring the body into a state whereby it believes it has been on the pill for a period of time sufficient to prevent pregnancy. It takes a few hours for that to happen, and if ovulation and intercourse have occurred proximately to each other to allow fertilization to occur before the hormones rise, EC will not be effective. This is why EC is more effective the sooner you take it, and has an efficacy rate less than that of regular hormonal birth control.

The technical explanation of how hormonal birth control work, for those who are interested, is as follows.

Under ordinary circumstances, the brain's hypothalamus produces a hormone called GnRH (gonadotropinreleasing hormone). This prompts the pituitary gland to release FSH (follicle stimulating hormone) which travels to the ovaries through the bloodstream and causes a follicle to grow. The development of the follicle produces estrogen, which after about 10 days reaches high enough levels to trip off a surge of LH (luteinizing hormone) from the pituitary gland. The ovarian follicle releases a mature egg into the fallopian tube about 24 hours after this surge of LH, and the empty follicle becomes known as the corpus luteum. The cells of the corpus luteum produce progesterone and estrogen, which together stimulate the uterine lining to thicken with blood in preparation for nurturing a fertilized egg. Once the corpus luteum wanes and the lining is left with no hormonal support, it sloughs off during your monthly period. The low levels of estrogen and progesterone also signal the hypothalamus to start the process over again.

Since oral contraceptives (OCs) provide a steady level of both progestin (a substitute for progesterone) and estrogen every day, and Norplant implants and DepoProvera provide steady daily levels of progestin, there is no signal to the hypothalamus to release GnRH and therefore no signal to the pituitary gland to produce FSH and LH. Because FSH stimulates the ovaries to grow egg follicles, and LH triggers ovulation, their absence causes the ovary to be relatively dormant, and no egg is produced to a point where it could be released. Hormonal contraception locks the system into the same late phase of the cycle on a continuous basis, perpetually skipping the allimportant release of GnRH .

Hormonal contraceptives work by damping down the two key hormones that trigger ovulation. Follicle stimulating hormone ( FSH), the substance that coaxes an egg towards maturity, is the first to be suppressed. Luteinizing hormone (LH), which ordinarily triggers release of the egg at mid-cycle, is also held down. Production of both these substances usually starts when the body senses a shortage of two other hormones: progesterone and estrogen, both produced in the ovaries. Hormonal contraceptives supply just enough of these substances to prevent start-up of the FSH/LH production cycle. Constant levels of estrogen and progesterone thus produce constant levels of FSH and LH, and the eggs remain dormant. (2)


There are a variety of hormones and chemicals that go into making sex what it is, and place each of us in the unique position of being what we are sexually. Understanding how these work, and how they interrelate to one another to cause the body to function the way it does is an important part of understanding how your sexuality functions.


(1) The Many Gendered Hormone, Natasha Mitchell.

(2) The PDR Family Guide to Women's Health

Pregnant woman relaxing