Read the order of peaks on an illustrative hormone graph
Invented relative series: oestrogen sampled maximum day 12; LH maximum day 13; ovulation stipulated day 14; progesterone maximum day 22. Dashed joins guide the eye, and series values are not clinical concentrations.
Section 16.5 · Sex hormones in humans
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 is the sampled LH maximum in this graph?
What you will learn
- Read each labelled hormone series independently
- Connect peak order with the stipulated ovulation event
Original teaching model.
| Feature | Meaning |
|---|---|
| Oestrogen | 9 relative units on day 12 |
| LH | 10 relative units on day 13 |
| Ovulation | Stipulated model day 14 |
| Progesterone | 9 relative units on day 22 |
| Model day | Relative values |
|---|---|
| 1 | FSH 4; LH 1; oestrogen 2; progesterone 1 |
| 5 | FSH 3; LH 1; oestrogen 3; progesterone 1 |
| 9 | FSH 2; LH 1; oestrogen 5; progesterone 1 |
| 12 | FSH 2; LH 2; oestrogen 9; progesterone 1 |
| 13 | FSH 4; LH 10; oestrogen 7; progesterone 1 |
| 14 | FSH 3; LH 7; oestrogen 4; progesterone 2 |
| 18 | FSH 1; LH 1; oestrogen 5; progesterone 7 |
| 22 | FSH 1; LH 1; oestrogen 6; progesterone 9 |
| 28 | FSH 4; LH 1; oestrogen 2; progesterone 1 |
Read each labelled hormone series independently
The original four-panel graph uses invented relative levels at model days 1, 5, 9, 12, 13, 14, 18, 22 and 28. Each panel identifies one hormone. The numbers are arbitrary teaching units, not clinical concentrations. Compare changes within one series; equal plotted numbers in different panels do not mean equal molar concentrations of different hormones.
In this model oestrogen reaches its sampled maximum of 9 units on day 12, LH reaches 10 units on day 13 and ovulation is stipulated on day 14. This order illustrates sustained high pre-ovulation oestrogen preceding the LH surge and release. The graph alone does not prove sustained duration: the teaching caption supplies the pre-ovulation condition. Sparse samples are not continuous measurements.
Connect peak order with the stipulated ovulation event
Progesterone is low before ovulation and rises after it, reaching the sampled maximum of 9 units on day 22. This pattern is consistent with corpus-luteum production after egg release and lining maintenance. FSH has its own labelled pattern, including early follicle stimulation; it should not be identified simply as whichever colour happens to have the tallest peak.
Dashed joins guide the eye between sampled points and are not measured intermediate values. The displayed peaks are sampled maxima, not proof of exact unsampled peak times. The graph illustrates a stated non-pregnant cycle and cannot diagnose ovulation, pregnancy or hormone levels in a real student. Use labels, values and the supplied event marker before giving an explanation.
Pause and explain
Why cannot equal oestrogen and progesterone numbers prove equal concentrations?
Worked example
Which sampled maximum comes first, oestrogen or LH?
Show the worked solution
- Read oestrogen day 12 and LH day 13.
- Compare their stated times rather than line colours.
Answer Oestrogen sampled maximum on day 12 precedes LH sampled maximum on day 13.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
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.
Order oestrogen maximum day 12, LH maximum day 13, ovulation day 14 and progesterone maximum day 22.
Give me a hint
Use the stipulated sampled days and event marker.
Compare my reasoning
- Place pre-release signals first.
- Place post-release progesterone maximum last.
Oestrogen sampled maximum → LH sampled maximum → stipulated ovulation → progesterone sampled maximum.
Look for these in your work
- Use correct order
- Retain sampled/stipulated wording
Explain why progesterone rises after the stipulated ovulation.
Give me a hint
Connect event with source tissue.
Compare my reasoning
- Name remaining follicle forming corpus luteum.
- Name progesterone production and lining maintenance.
After ovulation the remaining follicle forms corpus luteum, which produces progesterone supporting lining maintenance.
Look for these in your work
- Name source origin
- Give its target role
A learner reads a dashed line between days 18 and 22 as a measured personal hormone result. Correct the inference.
Give me a hint
Separate plotting joins from measured samples and real-person data.
Compare my reasoning
- Identify joins as visual guides.
- Identify all numbers as invented relative model levels.
The dashed join is not a measured intermediate value, and the series is invented teaching data rather than a personal hormone test.
Look for these in your work
- Give both data limits
- Avoid a diagnostic claim
Common mistakes
- Relative units are not clinical concentrations.
- Dashed joins are not additional measurements.
What can you explain now?
Why cannot equal oestrogen and progesterone numbers prove equal concentrations?
Compare with the explanation
Each is an arbitrary relative teaching series
The numbers are not matched clinical concentration units.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain read each labelled hormone series independently and connect peak order with the stipulated ovulation event. 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.