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.
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