Hormones cycle between the brain + the female reproductive organs.
Their ups + downs trigger periods, usually every 3-5 weeks… but not always, especially in the first year or two.
HERE’S WHAT HAPPENS:
- The brain sends hormones (LH + FSH) to the ovaries and uterus.
- LH + FSH tell the ovaries to make its hormones (estrogen + progesterone).
- Estrogen + progesterone ripen an egg + tell the uterus to build up a lining.
- An egg is released from an ovary (called ovulation).
- The egg passes through the fallopian tube and through the uterus.
- If it’s unfertilized, the egg exits the body through the vagina (it’s microscopic!)
- Then estrogen + progesterone levels drop and the uterus sheds its lining.
- The brain sends out more LH + FSH and the cycle starts again.
If you have an extra 4 minutes, watch this TED-Ed video on hormones and the menstrual cycle.
