Understand and track your menstruation

Menstrual Cycle: A symphony of hormones

When it comes to the menstrual cycle, periods are only the tip of the iceberg. In reality, it’s a whole symphony of hormones, orchestrated by the brain and performed by the reproductive organs, with the simple purpose of preparing you for childbirth.

Historically, periods were called "moons", as a reminder that the cycle is in sync with the moon. A typical menstrual period happens every 28 days, but the length of the menstrual cycle varies from one girl to another and a normal cycle can vary between 22 days and 32 days.

The hormones as maestros

Throughout the menstrual cycle, the ovary is stimulated by various hormones in your brain. Below is how a typical 28-day cycle evolves.

Day 1: The start of your period and menstrual cycle

The first day of your period is also the first day of your cycle. At this point, your hormones are still at a low point.

Day 1 - Day 14: Egg maturation in the ovaries

The ovaries are reproductive organs, whose purpose is to produce eggs and hormones. These two glands are located above the fallopian tube (the tube that carries an egg from the ovary to the uterus), on both sides of the uterus.

Ovaries contain thousands of potential eggs which are enclosed in an ovarian follicle, which is a cavity where the egg grows. Every month, one of these eggs matures under the influence of a hormone called FSH (Follicle Stimulating Hormone), which is produced by the pituitary gland. As the follicle matures, levels of estrogen rise considerably, making the lining of the uterus grow.

Day 14: Ovulation

During ovulation, another hormone, LH (Luteinizing Hormone), is secreted in large amounts halfway through the cycle. This LH surge triggers the ovary to release the mature egg in to the fallopian tube. If fertilization doesn’t happen within 24 hours of ovulation, the egg degenerates and the remaining cells develop into a small gland, called the corpus luteum.

Day 14 – Day 28: The luteal phase

After ovulation, the corpus luteum not only produces estrogen, but also large amounts of progesterone. Progesterone, promotes pregnancy by thickening the uterine lining (endometrium) so that it can accommodate a fertilized egg. In other words, progesterone is the pregnancy hormone. If the egg is fertilized, the hormone production continues, but if fertilization does not occur the hormone level drops and the uterus lining will shed in the form of a menstrual period. This is the beginning of a new cycle.


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