There are many hormones or critical players that play a role in your menstrual cycle. What do they all do and why are they important? What is the expected behavior? Let's dive into all that!
The start of a menstrual cycle is the period. The first day of the menstrual cycle is the first day of a woman’s period. A period indicates that you did not conceive in the previous cycle. Before the period, the endometrial lining of the uterus has thickened in preparation for nurturing a fertilized egg. If an egg is not fertilized, the body no longer needs that thick lining, so it begins to break down, and that’s why you have your period. You shed that thick uterine lining to prepare for the process to happen again, so the body has another chance to conceive.
Let’s go over the key players and each of these phases.
The prominent players in the menstrual cycle are follicle-stimulating hormone (FSH), estrogen, luteinizing hormone (LH), and progesterone. The menstrual cycle is broken up into two primary phases, separated by ovulation or the ovulatory phase.
The first phase is the follicular phase. The first part of the follicular phase is a woman’s period. During this time, estrogen and progesterone are low, which results in the top layers of the thickening uterine lining breaking down and shedding.
Around this time, the FSH levels begin to increase slightly, stimulating the development of several follicles in the ovaries. Each follicle contains an egg. Eventually, the FSH levels begin to decrease, and only one follicle continues to develop. This follicle starts to produce estrogen, the rise you start to see in the follicular phase.
As estrogen levels continue to increase, it signals to the brain's pituitary gland to begin releasing LH bursts. As a result, the LH levels rise, commonly known as the surge. When the LH levels peak, the egg is stimulated to be released from the ovary. This process is known as ovulation. Estrogen levels decrease during the surge.
Once the egg has left the ovary, the luteal phase begins. The LH and FSH levels decrease. The follicle ruptures after releasing the egg and forms a corpus luteum that produces progesterone. During most of this phase, the estrogen level is high but typically not as high as in the follicular phase. Progesterone and estrogen cause the uterus lining to thicken more to prepare for possible fertilization. If the egg is not fertilized, the corpus luteum will break down and no longer produce progesterone, the estrogen level decreases, and a period will occur. If the egg is fertilized, the corpus luteum continues to function during early pregnancy to help maintain the pregnancy.