Recently, we discussed the endocrine system, a system of glands that produce biochemical substances known as hormones. These include sex hormones, which play an important role, not only in pregnancy, but also in events leading to it. Oral contraceptives, also called birth control pills, consist of hormones that interfere with the signaling between hormones and the ovaries. In this series, we are discussing oral contraceptives from various angles, beginning with some common myths and the facts that resolve those myths. This is part one of the myths and facts component.
Myth: Ingesting female hormones in the form of oral contraceptives is unnatural and therefore dangerous.
Fact: Oral contraceptives contain an estrogen and a progestin component. These are female hormones, each of which consists of molecules that can differ in small ways from the molecules of your own estrogen and progestin hormones, but they do essentially the same thing. They carry a message to a part of your brain called the hypothalamus and also carry a message to a gland within the brain, called the pituitary gland. The anterior (forward-facing) part of the pituitary manufactures hormones called gonadotropins, called luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Meanwhile, the hypothalamus produces gonadotropin-releasing hormone (GnRH). When GnRH is produced, it stimulates the pituitary to release FSH and especially LH, which put the ovary through the ovulation cycle that causes your period and that can lead to pregnancy. The hormones of oral contraceptives prevent the hypothalamus from releasing GnRH, thus preventing the pituitary from being told to release gonadotropins. The contraceptive hormones also have a direct effect on the pituitary. It other words, they interfere in two ways with the process that otherwise sends gonadotropins to your ovaries. This prevents ovulation, a process that is necessary for the initiation of pregnancy. However, it is not unnatural, because these types of sex hormones normally circulate within your body. While your sex hormones normally prevent the release of gonadotropins for part of the ovulatory cycle, the sex hormones in birth control pills prevent the cycle itself, thus preventing ovulation from ever occurring.
Myth: Women menstruate, get their periods, while on oral contraceptives
Fact: Women do bleed while on the pill, but this is not technically menstrual bleeding. It’s not correct to call it a period, because the bleeding is not the result of an egg (ovum) being released (ovulation) and then not getting fertilized and not implanting. If it were the result of ovulation, if it were a true period, then oral contraceptives would not be preventing pregnancy. They would not be contraceptives. Bleeding in those taking oral contraceptives occurs a few days after you stop taking the hormones. Normally, you take pills containing the hormones for 21 days, and then you take seven days of placebo bills, so that you always have something to take and will not get confused with the schedule. Due to the lack of hormones to maintain it, the endometrium (the inner lining of the uterus) sheds, so you bleed. Because it is from the withdrawal of contraceptive hormones, it’s called withdrawal bleeding, and sometimes is also called breakthrough bleeding. Often, this bleeding is lighter and shorter than the bleeding of an actual period. Women who have special reasons to avoid bleeding after three weeks actually can continue taking the hormonal pills of the oral contraceptives in order to delay the next bleed. Not all, but many of the female astronauts who have spent intermediate amounts of time in space have chosen to do this. More commonly, Earth-bound women do it for special events, such as a wedding. You should follow such an unorthodox schedule of oral contraceptive, only if you do it in consultation with your obstetrician/gynecologist, and only on a temporary basis. It’s not healthy to do this for extended periods of time, because it causes a thickened endometrial lining to accumulate in your uterus. Also, the longer you delay your withdrawal bleeding, the heavier and longer the bleeding tends to be, since the endometrium has built up more material to shed.
In our next segment, Oral Contraceptives Myths and Facts Part 2, we’ll focus on the scheduling of how women take their pills.