GCSE Biology Hormones & the Menstrual Cycle Notes
Hormones control long-term changes in the body. Four hormones control the menstrual cycle and can be manipulated for contraception or fertility treatment.
Key concepts
- FSH
- Follicle-stimulating hormone from the pituitary — matures an egg in the ovary and stimulates oestrogen release.
- LH
- Luteinising hormone from the pituitary — triggers ovulation around day 14.
- Oestrogen
- From the ovaries — builds the uterus lining and inhibits FSH.
- Progesterone
- From the ovaries after ovulation — maintains the uterus lining and inhibits FSH and LH.
- Hormonal contraceptives (pill, patch, implant) use oestrogen and/or progesterone to prevent ovulation.
- IVF: FSH + LH stimulate multiple egg maturation; eggs are fertilised in the lab and implanted.
- Adrenaline (from adrenal glands) prepares the body for 'fight or flight' by increasing heart rate.
- Thyroxine (from thyroid) controls metabolic rate via negative feedback with the pituitary.
Worked example
Explain how the combined oral contraceptive pill prevents pregnancy.
- 1The pill contains oestrogen and progesterone.
- 2These inhibit FSH so no egg matures.
- 3They also inhibit LH so no ovulation occurs.
- 4Without an egg, fertilisation and pregnancy cannot happen.
Answer: Oestrogen and progesterone inhibit FSH and LH, so no egg matures or is released.
Common mistakes
✗ Mixing up FSH and LH.
✓ FSH matures the egg; LH releases it (ovulation).
✗ Saying oestrogen causes ovulation.
✓ Oestrogen thickens the uterus lining; LH triggers ovulation.
✗ Forgetting negative feedback for thyroxine.
✓ High thyroxine → pituitary makes less TSH → thyroid makes less thyroxine.
Quick check
Try these, then reveal the answers.
Which hormone triggers ovulation?Reveal answer
LH (luteinising hormone).
Where is progesterone produced?Reveal answer
In the ovaries (after ovulation).
One benefit and one risk of IVF.Reveal answer
Benefit: allows infertile couples to have a child. Risk: multiple births / low success rate / emotional and financial cost.
Exam tips
- Learn the four menstrual hormones with their source and role.
- For IVF/contraception, discuss both scientific mechanism and social/ethical points.
- Explain negative feedback loops step by step.
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Frequently asked questions
What is negative feedback?+
A control mechanism where a change triggers a response that reverses it, keeping the variable close to a set level.
How do hormonal contraceptives work?+
They use synthetic oestrogen and/or progesterone to inhibit FSH and LH, preventing egg maturation and ovulation.
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