In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action? Use your knowledge of the hormonal regulation of reproduction to predict the effect of a daily synthetic progesterone pill on (a) pituitary secretion of LH and FSH, and (b) ovarian secretion of estradiol and progesterone.

Video transcript

Welcome back. Let's look at our next question. It says how can taking progesterone pills prevent conception in women? Well, progesterone pills along with estrogen containing birth control pills inhibit the release of lutin. Izing hormone releasing hormone. So that's kind of a long name to remember. But as you can tell from its name and that then inhibition of that release suppresses the levels of FSH or follicle stimulating hormone and LH lutin izing hormone. And these two hormones are essential for follicular development and ovulation. So that prevents follicular development and ovulation. As we recall, hormones often have that twofold pathway where you have the initial hormone released from the hypothalamus that then triggers the release of something else from the pituitary which then causes those effects in the body. So again progesterone or estrogen in the birth control pill inhibits the release of that. Master Control. First hormone. They revolutionizing hormone releasing hormone suppressing the FSH and LH. So let's look at our answer choices here. Choice A says it prevents follicular development and that is our correct description here. Choice B says it prevents egg formation. Well this is close but not actually correct because the primary oocytes are present in the female from birth in those primordial follicles. What the progesterone and estrogen pills do is prevent the development of those follicles that will then lead to maturation and ovulation. But the primary oocytes are always are already present there themselves. So Choice B is not our correct answer. Choice C says it prevents the sperm from penetrating the egg? Um No that's not our answer. Um If for some reason the egg is released despite the action of the progesterone containing pill, the sperm can still penetrate the egg. It won't interfere with that. And finally, Choice D. It kills the sperm upon entering the ovary. And that is not our correct answer because that's not the method of action. So again, taking progesterone pills will prevent conception by preventing follicular development, which is Choice A. See you in the next video.