The Menstrual Cycle and Hormonal Control of Fertility
The menstrual cycle and hormonal control of fertility is IGCSE-only content on how four hormones (FSH, LH, oestrogen and progesterone), produced by the pituitary gland and the ovaries, interact to control the roughly 28-day cycle of egg maturation, ovulation and the build-up and breakdown of the uterus lining. Beyond GCSE Combined Science's brief overview, students must give the day-by-day sequence with named hormones and their sources, explain each hormone's effect on the ovary and uterus, and apply this to fertility treatments (for example, giving FSH and LH as fertility drugs, or oestrogen and progesterone as contraceptive hormones).
Before you start
Make sure you're comfortable with these topics first:
Method
- Learn the four hormones, where each is produced, and its main role: FSH (follicle-stimulating hormone, from the pituitary gland) causes an egg to mature in a follicle in the ovary, and stimulates the ovary to produce oestrogen; LH (luteinising hormone, from the pituitary gland) triggers ovulation (release of the mature egg); oestrogen (from the ovary) repairs and thickens the uterus lining, and inhibits FSH release while stimulating LH release; progesterone (from the corpus luteum, the remains of the follicle after ovulation) maintains the thickened uterus lining and inhibits both FSH and LH.
- Give the cycle as an ordered sequence over roughly 28 days, using day numbers as reference points: day 1 is the first day of menstruation, when the uterus lining breaks down and is lost (because progesterone and oestrogen levels have fallen); days 1-13, FSH rises and stimulates an egg to mature while oestrogen rises and repairs/thickens the uterus lining; around day 14, a surge in LH triggers ovulation; days 14-28, progesterone (from the corpus luteum) maintains the thickened lining ready for a fertilised egg to implant; if no fertilisation occurs, progesterone (and oestrogen) fall around day 28, triggering the lining to break down and the cycle to restart.
- Learn the negative and positive feedback relationships precisely: rising oestrogen initially inhibits FSH (stopping more than one egg maturing) but at high levels triggers the LH surge; progesterone inhibits both FSH and LH, which is why a maintained high progesterone level (as in pregnancy, or from a contraceptive pill) prevents another egg maturing or being released.
- For fertility-drug questions, reason from the roles above: giving a woman FSH and LH as a fertility drug stimulates her ovaries to mature and release eggs (used to treat infertility caused by a lack of these hormones, or in IVF to produce several eggs to collect).
- For hormonal contraceptive questions, reason the same way: a contraceptive pill containing oestrogen and/or progesterone works by maintaining constantly high levels of these hormones, which inhibit FSH (so no egg matures) and/or inhibit LH (so ovulation cannot be triggered).
- When interpreting a hormone-level graph over the 28-day cycle, read off the day on which each hormone peaks, describe the shape (rising, peaking, falling) using figures from the axis, and link each peak to the named event it causes (the LH peak to ovulation, the oestrogen peak just before it to lining repair) rather than only describing the shape.
Worked example
A doctor is investigating a patient's fertility and records her hormone levels over one menstrual cycle. FSH rises from day 1, peaks at day 12, then falls sharply. LH stays low until day 13, then spikes sharply at day 14 before falling. Using this data, identify the day on which ovulation most likely occurred, and explain your reasoning using the roles of FSH and LH.
- Recall the role of each hormone: FSH stimulates an egg to mature in the ovary; LH triggers ovulation (the release of the mature egg).
- Read the data for FSH: it rises and peaks at day 12, consistent with an egg maturing over the first half of the cycle.
- Read the data for LH: it stays low, then spikes sharply at day 14.
- Apply the hormone's known function to the data: since LH is the hormone that triggers ovulation, and its sharp spike occurs at day 14, this is when ovulation is expected to occur.
- Final answer: ovulation most likely occurred on day 14, shown by the sharp spike in LH at that point, which is the hormone responsible for triggering the release of the mature egg.
Practice questions
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Q1Name the gland that produces FSH and LH.Show answer
Answer: The pituitary gland.
Q2State the effect of FSH on the ovary.Show answer
Answer: It causes an egg to mature in a follicle.
Q3State the hormone that triggers ovulation.Show answer
Answer: LH (luteinising hormone).
Q4State the effect of progesterone on the uterus lining.Show answer
Answer: It maintains the thickened uterus lining, keeping it ready for a fertilised egg to implant.
Q5On approximately which day of a 28-day cycle does ovulation usually occur?Show answer
Answer: Around day 14.
Q6Explain why a hormonal contraceptive pill containing oestrogen and progesterone prevents pregnancy.Show answer
Answer: The constantly high level of oestrogen and progesterone from the pill inhibits FSH (so no egg matures) and inhibits LH (so no ovulation can be triggered), meaning no egg is released for fertilisation.
Exam-style questions
Written in the style of a IGCSE Science exam paper, with a full mark scheme.
State the source and the function of oestrogen in the menstrual cycle.
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A fertility clinic gives a patient FSH injections as part of an IVF treatment, then monitors her hormone levels. Before treatment, her natural FSH level averaged 4.2 units. After 8 days of injections, her FSH level averaged 15.6 units, and 6 mature eggs were collected from her ovaries. Calculate the percentage increase in FSH level caused by the treatment, and explain why raising FSH allowed multiple eggs to be collected.
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Explain how the four hormones FSH, LH, oestrogen and progesterone interact to control the menstrual cycle, including their effects on the ovary and the uterus lining, over the course of a 28-day cycle.
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Free printable worksheet
Want more practice on paper? Download the the menstrual cycle and hormonal control of fertility worksheet pack - 5 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.
This topic is chapter 5 of IGCSE Science Workbook, the whole course as one free printable PDF.
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