Explain the four-hormone sequence in a non-pregnant cycle
Conditional cycle loop: FSH → follicle/oestrogen → sustained high oestrogen/LH surge → ovulation/corpus luteum → progesterone maintenance and feedback → hormone decline and menstruation if pregnancy is not established.
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall endocrine glands, blood-borne hormones, ovaries, testes, uterine lining, ovulation and implantation.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which structure secretes FSH and LH?
What you will learn
- Connect the four hormones with ovarian and uterine events
- Explain return to the next menstrual cycle
Original teaching model.
| Feature | Meaning |
|---|---|
| Early | FSH stimulates follicle and oestrogen |
| Before release | Sustained high oestrogen → LH surge |
| After release | Corpus luteum → progesterone support |
| Return condition | No established pregnancy; support falls |
Connect the four hormones with ovarian and uterine events
Start the explanation with pituitary FSH stimulating ovarian follicle development and oestrogen production. Oestrogen supports uterine-lining rebuilding and, at usual lower/moderate levels, limits FSH through negative feedback. The pituitary and ovary are different hormone sources connected by blood transport and target responses, not one structure releasing all four hormones.
Sustained high oestrogen before ovulation promotes an LH surge. Pituitary LH then triggers ovarian egg release and supports corpus-luteum formation/function. This order includes the intermediate signal between high oestrogen and ovulation. It does not describe fertilisation, which additionally requires sperm–egg nuclear fusion.
Explain return to the next menstrual cycle
After ovulation the corpus luteum produces progesterone and oestrogen. Progesterone maintains the prepared uterine lining and inhibits FSH/LH secretion. These effects support the post-ovulation phase and reduce further follicle stimulation. A full answer follows both the forward effect on the uterus and the feedback effect on pituitary output.
If pregnancy is not established, the corpus luteum breaks down; progesterone and oestrogen fall, the lining loses support and menstruation begins. Reduced inhibition allows FSH stimulation to rise again. The original sequence is an explanatory loop with conditional return, not a guarantee of ovulation, fertilisation or pregnancy in every individual cycle.
Pause and explain
Which chain explains the next menstruation?
Worked example
Complete the missing link: sustained high oestrogen → ? → ovulation.
Show the worked solution
- Name pituitary LH surge.
- Link its action with ovarian release.
Answer Sustained high pre-ovulation oestrogen → LH surge → ovulation.
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Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Write the sequence from FSH to ovulation using oestrogen and LH.
Give me a hint
Include source, developing follicle and feedback condition.
Compare my reasoning
- FSH stimulates follicle development/oestrogen.
- Sustained high oestrogen stimulates LH surge; LH triggers release.
Pituitary FSH stimulates ovarian follicles and oestrogen production; sustained high pre-ovulation oestrogen promotes the pituitary LH surge, which triggers ovulation.
Look for these in your work
- Use all three hormones
- State the high-level condition
Explain post-ovulation lining maintenance and reduced pituitary stimulation.
Give me a hint
Use corpus luteum and progesterone.
Compare my reasoning
- Name progesterone from corpus luteum.
- Connect maintenance with inhibited FSH/LH.
Corpus-luteum progesterone maintains uterine lining and inhibits FSH and LH secretion, reducing further ovarian stimulation.
Look for these in your work
- Name source and lining effect
- Include feedback
Explain how a non-pregnant cycle returns to day one.
Give me a hint
Trace ovarian breakdown and hormone withdrawal.
Compare my reasoning
- Name corpus-luteum breakdown with progesterone/oestrogen fall.
- Name uterine shedding and relief of FSH inhibition.
Without established pregnancy, corpus luteum breaks down, progesterone/oestrogen decline and lining sheds at menstruation; reduced inhibition allows FSH stimulation for another cycle.
Look for these in your work
- Include source and target changes
- Keep the condition explicit
Common mistakes
- Do not omit intermediate hormones.
- The return branch depends on pregnancy not being established.
What can you explain now?
Which chain explains the next menstruation?
Compare with the explanation
Corpus-luteum breakdown → hormone decline → lining shedding
It connects ovarian source change with uterine response.
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Make it stick
Explain connect the four hormones with ovarian and uterine events and explain return to the next menstrual cycle. Follow the event arrows or graph labels before opening the solutions.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.