CB7.3Hormones in human reproduction: menstrual cycle, contraception, fertility treatments (IVF, clomifene)

Notes

Hormone	Produced by	Effect
FSH (follicle-stimulating hormone)	Pituitary gland	Stimulates follicle maturation in ovary; stimulates oestrogen secretion
LH (luteinising hormone)	Pituitary gland	Surge triggers ovulation; stimulates corpus luteum to produce progesterone
Oestrogen	Ovary (follicle)	Repairs uterine lining; triggers LH surge (positive feedback); inhibits FSH
Progesterone	Ovary (corpus luteum)	Maintains uterine lining; inhibits FSH and LH

Cycle summary (28 days):

Day 1–5: menstruation (lining shed).
Day 5–13: lining rebuilds; oestrogen rises.
Day 14: LH surge → ovulation.
Day 15–28: progesterone from corpus luteum; if no fertilisation → progesterone falls → lining breaks down.

Combined pill: oestrogen + progesterone → inhibit FSH → no follicle maturation → no egg released.
Progesterone-only pill: thickens cervical mucus → sperm cannot pass.
Implant/injection: slow-release progesterone.

Clomifene: blocks oestrogen receptors in pituitary → FSH and LH levels rise → stimulates ovulation. Used for women who do not ovulate regularly.
IVF: FSH given to stimulate multiple egg production; eggs collected; fertilised with sperm in lab; 1-2 embryos implanted.

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Question 15 marks
Menstrual cycle hormones
(5 marks) Describe the roles of FSH, oestrogen and LH in the first half of the menstrual cycle (days 1–14).
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AI-generated · claude-opus-4-7 · v3-edexcel-combined-science
Question 23 marks
Clomifene therapy
(3 marks) Explain how clomifene can be used as a fertility treatment.
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CB7.3 — Hormones in reproduction: menstrual cycle and fertility

6-card SR deck for Edexcel Combined Science topic CB7.3

6 cards · spaced repetition (SM-2)