Primers to help you better help understand how birth control works: The Menstrual Cycle and FSH and LH (Gonadotropic Hormones)
If a woman took a pill containing estrogen everyday and raised the estrogen level in the blood, that would inhibit her pituitary from releasing Follicle Stimulating Hormone (FSH), which means the ovarian follicles will NOT develop in her ovaries. FSH is what causes ovarian follicles to grow, so you can’t get pregnant if there’s no egg growing in the ovary.
What if she takes a pill everyday that has progesterone in it? It will raise progesterone in her blood which will inhibit the pituitary from releasing Luteinizing Hormone (LH). You need LH to make an egg ovulate, so if progesterone causes LH to be inhibited, there egg will never ovulate even if an ovarian follicle had developed.
In fact, most birth control pills contain both estrogen and progesterone and there’s hundreds of variations of them. Estrogen inhibits FSH so ovaries wont develop. Progesterone inhibits LH so the egg can’t ovulate. Got it? Okay, let’s move on.
How come women who take birth control pills have a period?
Hypothalamus GnRH -> Pituitary releases FSH -> Ovaries to secrete Estrogen
Hypothalamus GnRH -> Pituitary releases LH -> Ovaries to secrete Progesterone
Birth control pills for women come in many different cute cases. Heart shaped, tear shaped, etc. If they did it for a guy, it would come in a cardboard box because they could care less. They always have 28 pills because the cycle lasts 28 days. As I use the word “birth control pills” obviously women do take these to NOT get pregnant, but that’s not the only reason why they are doing it. It’s useful for those that have very irregular menstrual cycles or have amenorrhea (the absence of menstruation flow). Birth control causes them to have perfect menstrual cycles, so it doesn’t always mean they are taking BC for not getting pregnant.
A woman is supposed to take 1 of these each day from the pill case. Commonly, many of the pills are different colors. Let’s assume the first 7 are white, then the next 7 are red, then the remaining pills are going to be green. The purpose for the color, other than being decorative, are to indicate what’s in them. The white ones don’t have anything in them, you don’t even have to take them, they are placebo pills, the point of them is so the woman stays in the habit of taking the pill everyday. The red ones have increasing levels of estrogen. The green ones have increasing levels of progesterone.
The estrogen and progesterone inhibit the pituitary gland but they also affect their own uterus, just like these chemicals normally would. With increasing levels of estrogen, they also cause a slight thickening of the endometrial lining, just like estrogen naturally would. Then around day 15, 16, 17, we take pills with increasing amounts of progesterone, which not only inhibits LH, but causes significant thickening of the endometrial lining, mimicking her own menstrual cycle. Instead of the progesterone coming from her ovaries, it’s coming from the pill.
When she finishes pill #28 which has progesterone in it, and her next pill is the white one, with nothing in it, all of a sudden the progesterone level drops. What happens when progesterone level drops? Shedding of the endometrial lining (Menstruation!). Normally her own ovaries stop the progesterone which causes the shedding. She will have this perfect menstrual cycle and the whole thing repeats over again. So the uterus is functioning normally, if not better.
If you forget to take the pill, what do you do?
It depends on WHICH pill you forgot to take and what formulation you are taking. Every single one has different instructions. Some say take 2 the next day. Some say continue like normal. Some say ALL BETS ARE OFF, don’t have sex for 2 weeks.
Summary
| Hormone | Source | Functions | Factors that stimulate its release | Factors that inhibit (or decrease) its release |
|---|---|---|---|---|
| Follicle Stimulating Hormone (FSH) | Adenohypophysis (Anterior Pituitary Gland) | In Males: Stimulates sperm production.In Females: Stimulates growth of ovarian follicles and estrogen secretion. | GnRH | In males: increased InhibinIn females: Increased Estrogen |
| Luteinizing Hormone (LH) | Adenohypophysis (Anterior Pituitary Gland) | In males: Stimulates Testosterone secretion.In females: Stimulates ovulation & progesterone secretion | GnRH | In males: Increasing testosteroneIn females: Increasing progesterone |
| Human Chorionic Gonadotropin (HCG) | Chorionic Villi (of the placenta/outer sac) | Stimulates the follicle cells of the Corpus Luteum to secrete Progesterone (which maintains vascularity of endometrium of uterus during pregnancy. | Pregnancy (**the test for pregnancy is the detection of HCG) | Termination of pregnancy. |
Next up… the four essential hormones that are essential for life.
