Understanding Your Menstrual Cycle

By Dr. Alexsia Priolo

I like to think of the menstrual cycle as the fifth vital sign. For women and people who menstruate, the menstrual cycle can actually tell you a lot about your health. The last time many women truly learned about their cycle was in the sixth grade. Therefore, I’m sharing the three main phases of the cycle (based on a 28 day cycle) and what happens during each!

Follicular Phase

Days: 1 to 13

The first day of bleeding (not spotting), marks Day 1 of your cycle. This is a pretty active phase of your cycle as your endometrial lining is being shed, a few eggs are maturing (and waiting to be fertilized), and your endometrial lining begins to grow again.

The follicle stimulating hormone (FSH) will act directly on your ovarian follicles causing some of them to mature. These maturing eggs begin to release estrogen, causing a spike to occur, which in turn will lead to a spike in lutenizing hormone (LH) thereby causing ovulation to occur in the most mature follicle of the ovary.

Ovulation

Day: 14

First things first, not everyone experiences an exact 28 day cycle. Even if they do, ovulation may not actually occur! A couple of signs to detect if ovulation is happening is to use ovulation test strips, assess for fertile cervical mucus (it resembles and egg white) and a slight rise in body temperature.

Around day 14, the spike of LH will cause the ovary to release the most mature follicle. This follicle will begin it’s decent to the fallopian tube. This is the optimal time for sperm and egg to meet, and for fertilization to occur.

Luteal Phase

Days: 15 to 28

When the egg is released from the follicle, the follicle becomes the corpus luteum (CL). The CL is the remainder of the matured follicle and sticks around to secrete the hormones: estrogen and progesterone.

If fertilization between egg and sperm has occurred, the fertilized egg will travel from the fallopian tube to the uterus and implant in the uterine wall. If fertilization has not occurred, fourteen days later, the CL will degenerate causing a decrease in progesterone leading to shedding of the endometrial lining (your period!).

What’s Next?

Overall, this is a really simplistic overview of your cycle – the hormones, especially estrogen and progesterone, have other significant roles within your body. Not to mention, other hormones and glands control and affect the function of these hormones.

In addition, certain conditions (for example: PCOS) and life stages (ie: perimenopause and menopause) can affect your hormones and cycle, and result in signs and symptoms that you may not deem as typical for you.

If you haven’t been paying close attention to your cycle, now is the time to start. I often have my patients begin to get a basic understanding of their cycle by tracking it using an app (my favourite is Clue). Not only can they chart when it begins, they can get an average length of their cycle, and chart any symptoms they experienced during or between cycles (ie: sore breasts, headaches, cramps, increased cervical fluid, etc.) I use that information to see which hormones are out of balance and to formulate a plan of action!