The Menstrual Cycle and Hormones
Hormones control the monthly cycle and prepare for pregnancy.
About this topic
The menstrual cycle, about 28 days, is controlled by hormones. FSH from the pituitary stimulates a follicle to develop in an ovary, which releases oestrogen, thickening the uterus lining. A surge in LH triggers ovulation around day 14. The empty follicle makes progesterone, which maintains the lining; if no pregnancy occurs, hormone levels fall and menstruation begins.
The hormones work by negative and positive feedback. Oestrogen at first inhibits FSH, but a high level stimulates the LH surge. Progesterone then inhibits FSH and LH to prevent more eggs developing. If the egg is fertilised, the embryo produces a hormone that keeps progesterone high, so the lining is kept and the cycle pauses.
Days one to five are menstruation, when the lining is shed; days six to thirteen the lining rebuilds; ovulation is at about day 14; and days fifteen to twenty-eight the lining is maintained. A graph of hormone levels shows peaks in sequence. The fertile window is the few days around ovulation.
Hormonal contraceptives use oestrogen and progesterone to prevent FSH and LH rising so no egg is released, while fertility treatments use FSH to stimulate eggs. A common misconception is that every cycle is exactly 28 days; many people vary, especially in teenage years.
Key ideas
- FSH, LH, oestrogen, progesterone
- Ovulation around day 14
- Lining sheds if no fertilisation
Quick check
Use cases: where The Menstrual Cycle and Hormones helps
- Homework: review the key idea behind The Menstrual Cycle and Hormones before you start a problem set.
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Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is The Menstrual Cycle and Hormones?
Hormones control the monthly cycle and prepare for pregnancy.
What will I learn in The Menstrual Cycle and Hormones?
FSH, LH, oestrogen, progesterone. Ovulation around day 14. Lining sheds if no fertilisation.
Is The Menstrual Cycle and Hormones part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the The Menstrual Cycle and Hormones lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study The Menstrual Cycle and Hormones?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
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