Understanding your menstrual cycle

Understanding your menstrual cycle

Have you ever wondered what goes on during your menstrual cycle? Or what's behind the emotional ups and downs you may feel as your cycle progresses? Read on for a basic description.

Your cycle is based on a delicate balance of two hormones, estrogen and progestin. The levels of these hormones change as your cycle progresses. The charts below take you through a typical 28-day cycle. Of course, it's important to keep in mind that every woman's cycle is slightly different. Some women's cycles are as short as 23 days. Others are as long as 35. But regardless of the timing, the basic sequence of events is the same.

Day 1: Your period

What's happening in your body
The first day of your period is considered Day 1 of your cycle. At this time, estrogen and progesterone, the two main reproductive hormones, are at low levels.

Day 5: One egg is selected

What's happening in your body
Inside the ovary, each egg is surrounded by a layer of cells called a follicle. As an individual egg develops, the follicle releases increasing amounts of estrogen.

Days 6-14: Preparing for ovulation

What's happening in your body
Toward the end of this stage, estrogen levels drop slightly while levels of hormones known as androgens rise. Levels of progesterone and androgens, such as testosterone, are flat and then increase at the end of this stage.

What are androgens?
Men and women both have hormones known as androgens in their bodies. The main androgen is called testosterone. It helps maintain muscle, bone mass, and a healthy sex drive in both men and women, and helps regulate a woman's menstrual cycle. Since women need a much smaller amount of testosterone than men, they tend to have very low levels of androgens.

Around Day 14: Ovulation

What's happening in your body
The follicle surrounding the egg breaks open and the ovaries release the egg into the fallopian tube so it can be fertilized by sperm. The follicle stays behind in the ovary.

Days 15-28: After ovulation

What's happening in your body
If the egg that was released is not fertilized, estrogen and progesterone levels drop and the lining of the uterus gets ready to be shed. Your next period begins and the cycle starts again.