Let’s start from the beginning. After your period, your body starts to build up the lining of your uterus again, preparing a home in which to grow a baby. While this is happening, the follicles also start to develop, getting bigger and bigger until one bursts and releases an egg. This #eggdrop is called ovulation.
FSH or Follicle Stimulating Hormone is the hormone responsible for stimulating those immature eggs that live in the ovarian follicles (the little sacs of fluid that eggs call home) to grow up. FSH is regulated by cells in the pituitary gland. FSH is a real overachiever, working hard to regulate the development, growth, pubertal maturation,(1) and reproductive processes of the body. For example, FSH levels determine when a person starts puberty, and when they enter menopause. Similarly, in biological males, FSH levels determine testes function and sperm count.
OKAY, AND LH?
LH or Luteinizing Hormone is another hormone regulated by the pituitary gland, and is what causes the egg to actually drop it like it’s hot. LH is like the jelly to FSH’s peanut butter—after FSH completes its job of growing the egg, LH takes over to make that egg droooppp.
HERE’S HOW IT ALL GOES DOWN
During the first part of the cycle, FSH rises enough so that one of those lucky follicles will mature. After prepping that egg, ovaries start releasing estrogen, which halts FSH production and tells your pituitary gland to start releasing LH. LH levels continue to increase until—POW!—the mature follicle releases the egg and ovulation has occurred. That now ruptured follicle turns into the corpus luteum,(2) and starts releasing progesterone to build up a uterine lining, creating a cozier environment for the possible pregnancy. If sperm are a no show, progesterone levels begin to drop, and so begins your period.
THIS IS COOL, BUT HOW DO I USE THIS INFO PRACTICALLY?
I know this seems like a lot of Biology 101—but here’s why it’s important to know: FSH acts as a kind of regulator to ensure that all reproductive systems reach go! If you’re trying to conceive, experience irregular menstrual cycles, or are showing delayed OR early signs of puberty, testing(3) your FSH and LH levels can be extremely valuable.
DO THOSE AMAB HAVE THESE HORMONES?
They too have fluctuating levels of FSH and LH that act in synergy! But for them, LH stimulates the cells that produce testosterone, while FSH, which is regulated by testosterone, stimulates the cells of the testes, to trigger sperm production, AKA spermatogenesis.
So basically this pair is responsible for all creation. NBD.
Written by: Morgan De Santo, reproductive health specialist
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(1) Medline. “Puberty.” MedlinePlus, U.S. National Library of Medicine, 7 Feb. 2019, medlineplus.gov/puberty.html.
(2) Baerwald, A. R., et al. “Form and Function of the Corpus Luteum during the Human Menstrual Cycle.” Ultrasound in Obstetrics and Gynecology, vol. 25, no. 5, 2005, pp. 498–507., doi:10.1002/uog.1891.
(3) Medline. “Follicle-Stimulating Hormone (FSH) Blood Test: MedlinePlus Medical Encyclopedia.” MedlinePlus, U.S. National Library of Medicine, medlineplus.gov/ency/article/003710.htm.