Know Thy Cycle Part II: The Chemicals Involved

So how does your body know to cycle through a monthly symphony? How does the egg know when to burst out of the ovary? Why does the lining shed each month? The answer: Chemical signals, aka HORMONES.

I use the acronym FELOP to remember the primary hormones of the menstrual cycle and the order in which they are produced. The acronym was developed by Toni Weschler, the wonderfully informative author of Taking Charge of Your Fertility.

The hormones and their timing throughout your cycle are important to understand because having deficiencies in one or many can provide information on how to go forward with any treatment you might seek.


FSH is produced in the brain by the anterior pituitary gland during the first and second week of your cycle. It stimulates on average between 15-20 follicles each month to mature in each ovary. As the follicles are stimulated, one will grow a bit faster than the others to eventually release the lucky egg of the month. The growing follicles themselves produce the next hormone:

As the follicles mature they ooze estrogen into the blood stream. When the dominant follicle has reached it fullest potential, the concurrent increasing amount of estrogen in the blood stream will trigger the pituitary gland to release our next hormone:

The spike in LH in the blood stream causes the mature follicle to release the egg from the ovary. This process of release is known to us as:

The follicular sac left behind after ovulation is called the Corpus Luteum. It in itself produces our next hormone called:

Progesterone thickens the lining of the uterus, preparing to receive a fertilized egg. The lining will be the embryo’s first source of nourishment after implantation.

Not only must all of the hormones listed above release in the most precise dosages at the right time to trigger the release of an egg, they are also responsible for the environment inside of the uterus. Sperm, try as the might, can’t get through the cervix if a woman doesn’t produce enough estrogen to thin out her cervical mucus. If progesterone is too low, endometrial tissue may not thicken- and if the uterine lining is too thick (or even two thin) by even a millimeter, an embryo may miss its chance to attach to the walls of the uterus. And I bet you can already guess what is super susceptible to stress, sleep and diet and lifestyle… You got it: Your hormones.

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