BiologyCBSE Class 12 · Human Reproduction

Menstrual Cycle and Its Hormonal Control

Updated 15 October 2026 · Fact-checked

The menstrual cycle is the roughly 28-day reproductive cycle of female primates. It has a menstrual phase (days 1-5), a follicular phase in which FSH and LH grow the Graafian follicle and oestrogen rebuilds the endometrium, ovulation around day 14 triggered by the LH surge, and a luteal phase in which the corpus luteum secretes progesterone.

Understand Menstrual Cycle and Its Hormonal Control

What it is. The reproductive cycle of female primates (monkeys, apes and humans) is the menstrual cycle. The first menstruation at puberty is menarche. In women, menstruation repeats on average every 28 or 29 days; the events from one menstruation to the next form one cycle, and one ovum is released in the middle of each cycle. Cycles stop at about 50 years of age: menopause. Regular cycles indicate a normal reproductive phase, which lasts from menarche to menopause.

Phase 1: Menstrual phase (about days 1-5). Menstrual flow lasts 3-5 days. It results from the breakdown of the endometrial lining of the uterus and its blood vessels, which leaves the body as a liquid through the vagina. Menstruation happens only if the released ovum is not fertilised. Missing a period may indicate pregnancy, but it can also have other causes such as stress or poor health.

Phase 2: Follicular (proliferative) phase (about days 6-13).

In the ovary, primary follicles grow into a fully mature Graafian follicle.
In the uterus, the endometrium regenerates by proliferation.
Hormones: the pituitary's gonadotropins (FSH and LH) rise gradually; they stimulate follicular development and the secretion of oestrogens by the growing follicles. Rising oestrogen rebuilds the endometrium.

Phase 3: Ovulation (about day 14). Both LH and FSH peak in the middle of the cycle. The rapid rise of LH to its maximum, the LH surge, makes the Graafian follicle rupture and release the ovum (secondary oocyte): ovulation.

Phase 4: Luteal (secretory) phase (about days 15-28).

The remaining parts of the Graafian follicle become the corpus luteum.
The corpus luteum secretes large amounts of progesterone, which maintains the endometrium, keeping it ready for implantation and the events of pregnancy.
If fertilisation occurs: the corpus luteum is maintained, all events of the cycle stop and there is no menstruation during pregnancy.
If not: the corpus luteum degenerates, progesterone falls, the endometrium breaks down and menstruation starts a new cycle.

Flow chart (ovary and uterus together):
FSH, LH rise → follicle grows and secretes oestrogen → endometrium proliferates → LH surge (day 14) → ovulation → corpus luteum → progesterone → endometrium maintained → no fertilisation → corpus luteum degenerates → progesterone falls → menstruation.

Reading the hormone graph (a favourite case-based item). Over a 28-day cycle:

LH: low, then a sharp, tall peak just before day 14 (the surge), then low.
FSH: also peaks at mid-cycle, but less sharply than LH.
Oestrogen: rises through the follicular phase to a peak just before ovulation; a smaller rise in the luteal phase.
Progesterone: low in the follicular phase; high in the luteal phase (from the corpus luteum); falls at the end if there is no pregnancy.
Endometrium: thinnest after menstruation, thickening through the follicular phase, thickest and most glandular in the luteal phase.

Draw and label: the menstrual cycle chart. Checklist: a time axis from day 1 to 28 with phase bands; four panels stacked: (1) pituitary hormones LH and FSH with the mid-cycle peak, (2) ovarian events: developing follicle → Graafian follicle → ovulation → corpus luteum → degenerating corpus luteum, (3) ovarian hormones oestrogen and progesterone, (4) endometrium thickness. Labels: menstrual phase, follicular phase, ovulation, luteal phase, LH surge, Graafian follicle, corpus luteum, endometrium.

Menstrual Cycle and Its Hormonal Control: key facts

Phases of a 28-day cycle: $menstrual (1-5) \to follicular (6-13) \to ovulation (14) \to luteal (15-28)$; Day numbers are typical; flow lasts 3-5 days.
Trigger for ovulation: $LH surge \Rightarrow Graafian follicle ruptures \Rightarrow ovum released$; LH and FSH both peak mid-cycle; the LH peak is the trigger.
Follicular phase hormones: $FSH, LH ↑\Rightarrow follicle grows \Rightarrow oestrogen ↑\Rightarrow endometrium regenerates$; Also called the proliferative phase.
Luteal phase hormones: $corpus luteum \Rightarrow progesterone ↑\Rightarrow endometrium maintained$; Also called the secretory phase.
Why menstruation happens: $no fertilisation \Rightarrow corpus luteum degenerates \Rightarrow progesterone ↓\Rightarrow endometrium breaks down$; In pregnancy the cycle stops and there is no menstruation.

How to answer Menstrual Cycle and Its Hormonal Control questions

Board questions give a diagram or graph of the cycle, or a case of a missed or irregular period. Work phase by phase.

1Mark the day ranges and name each phase: menstrual, follicular (proliferative), ovulatory, luteal (secretory).
2For each phase, give three things: ovarian event, main hormone, uterine (endometrium) event.
3On a graph, identify hormones by shape: tall narrow mid-cycle peak = LH; high only after day 14 = progesterone; peak just before ovulation = oestrogen.
4For 'what if' cases, trace the chain: hormone changes → ovarian effect → endometrium → whether menstruation occurs.
5If fertilisation is mentioned, say that the corpus luteum persists, progesterone stays high and menstruation stops.
6State the source of each hormone (pituitary: FSH, LH; follicle: oestrogen; corpus luteum: progesterone) as it usually carries a mark.

Menstrual Cycle and Its Hormonal Control in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Corpus luteum and the missed period

Suppose a woman with regular 28-day cycles notices that her period, due on day 29, has not come by day 35, and a home test later confirms pregnancy.

Explain, in terms of the corpus luteum and progesterone, why menstruation did not occur, and why a missed period alone does not prove pregnancy.

Try it first, then show the solutionSolution

After ovulation on about day 14, the Graafian follicle became the corpus luteum and secreted progesterone, which kept the endometrium intact.
The ovum was fertilised, so the corpus luteum did not degenerate; progesterone stayed high, the endometrium did not break down and no menstrual flow occurred. During pregnancy all events of the cycle stop.
Without fertilisation the corpus luteum would have degenerated around the end of the cycle, causing menstruation. But a period can also be missed because of stress or poor health, so a test is needed to confirm pregnancy.

Answer: Fertilisation kept the corpus luteum active, so progesterone maintained the endometrium and menstruation stopped; stress or poor health can also delay a period.

Memory hook: No corpus luteum collapse, no period.

Tricks to remember Menstrual Cycle and Its Hormonal Control

Short memory aids. Say each one aloud once, then use it on a question the same day.

M-F-O-L
My Friend Often Laughs: Menstrual, Follicular, Ovulatory, Luteal.
Use it when: Phase order.
Follicle = oEstrogen, Luteum = Progesterone
First half Estrogen (E comes early), second half Progesterone (P for pregnancy-prep).
Use it when: Matching ovarian hormones to phases.
LH = Let Her (egg) go
The LH surge lets the egg go: ovulation.
Use it when: Naming the trigger for ovulation.

Menstrual Cycle and Its Hormonal Control: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Phases from a diagram · 3 marks · Short answerBoard level

In a diagram of a 28-day menstrual cycle, give the technical terms for days 1-5, days 6-13, day 14 and days 15-28, and name the main hormone acting on the uterus in the second and the last of these.

Try it first, then show the solutionSolution

Days 1-5: menstrual phase; days 6-13: follicular (proliferative) phase (1 mark).
Day 14: ovulation (ovulatory phase); days 15-28: luteal (secretory) phase (1 mark).
Follicular phase: oestrogen from growing follicles; luteal phase: progesterone from the corpus luteum (1 mark).

Answer: Menstrual, follicular, ovulatory, luteal; oestrogen (follicular), progesterone (luteal).

Example 2: Correct statements · 1 mark · MCQBoard level

Select the correct statements: (i) The corpus luteum secretes progesterone. (ii) Only FSH peaks in the middle of the cycle. (iii) The LH surge induces rupture of the Graafian follicle. (iv) The luteal phase follows menstruation.

Try it first, then show the solutionSolution

(i) True. (ii) False: both LH and FSH peak at mid-cycle.
(iii) True. (iv) False: the follicular phase follows menstruation; the luteal phase follows ovulation.

Answer: (i) and (iii).

Example 3: Why menstruation occurs · 2 marks · Very short answerHarder board level

Explain why menstruation occurs only when the ovum is not fertilised.

Try it first, then show the solutionSolution

After ovulation, the corpus luteum secretes progesterone, which maintains the endometrium for implantation (1 mark).
If fertilisation does not occur, the corpus luteum degenerates, progesterone falls, the endometrium and its blood vessels break down, and menstrual flow follows. If it does occur, the corpus luteum persists and menstruation stops (1 mark).

Answer: Without fertilisation the corpus luteum degenerates, progesterone falls and the endometrium is shed.

Example 4: Two graphs compared · 3 marks · Short answerHOTS / competency

Suppose Graph 1 of a woman shows a normal mid-cycle LH peak and high progesterone from day 15 to 28, falling at day 28. Graph 2 of another woman shows the same LH peak but progesterone stays high beyond day 28 and no menstruation follows. (a) What event explains Graph 2? (b) Which structure is responsible for the high progesterone in both? (c) What would happen to the endometrium in each by day 30?

Try it first, then show the solutionSolution

(a) Fertilisation (and pregnancy): the corpus luteum has not degenerated (1 mark).
(b) The corpus luteum, formed from the ruptured Graafian follicle after ovulation (1 mark).
(c) Graph 1: progesterone has fallen, so the endometrium breaks down and menstruation begins. Graph 2: progesterone keeps the endometrium intact for the pregnancy (1 mark).

Answer: (a) Pregnancy (b) corpus luteum (c) shed in Graph 1; maintained in Graph 2.

Example 5: Hormones and the Graafian follicle · 2 marks · Very short answerHarder board level

Name the gonadotropins that stimulate follicular development and state how the developing follicle in turn affects the uterus. What triggers ovulation?

Try it first, then show the solutionSolution

FSH and LH from the anterior pituitary rise gradually and stimulate follicle growth; the growing follicles secrete oestrogens, which make the endometrium regenerate (1 mark).
At mid-cycle the LH surge causes the Graafian follicle to rupture and release the ovum (1 mark).

Answer: FSH and LH grow the follicle; follicle oestrogen rebuilds the endometrium; LH surge triggers ovulation.

Example 6: Irregular cycles · 4 marks · Case-basedHOTS / competency

Suppose a 17-year-old girl has cycles ranging from 20 to 45 days, and tests show that her LH does not show a clear mid-cycle surge in many cycles. (a) Which event is likely to be missing in those cycles? (b) Which structure will then not form, and which hormone will remain low? (c) Explain why her cycle length becomes unpredictable.

Try it first, then show the solutionSolution

(a) Ovulation: without an LH surge the Graafian follicle does not rupture (1 mark).
(b) No corpus luteum forms, so progesterone remains low (1 mark).
(c) The orderly sequence (follicle → LH surge → corpus luteum → its degeneration → menstruation) sets the timing of the next period. Without ovulation and a corpus luteum, the endometrium is built up by oestrogen and is shed irregularly, so cycle length varies (2 marks).

Answer: No ovulation → no corpus luteum → low progesterone → endometrium shed at irregular times.

Where students lose marks in Menstrual Cycle and Its Hormonal Control

The slips examiners see most often, and what to write instead.

Mistake: Saying FSH triggers ovulation
Both FSH and LH peak together.
Wrong working
The FSH surge causes ovulation.
Right working
The LH surge causes rupture of the Graafian follicle and ovulation.
Do this: LH = Let Her egg go.
Usually costs: 1 mark.
Mistake: Writing that the corpus luteum secretes oestrogen only
Hormones of the two ovarian structures get swapped.
Wrong working
Corpus luteum secretes oestrogen to rebuild the endometrium.
Right working
Corpus luteum secretes large amounts of progesterone, which maintains the endometrium.
Do this: Follicle → oestrogen; corpus luteum → progesterone.
Usually costs: 1 mark.
Mistake: Mixing up 'regenerates' and 'maintains'
Students use one verb for both hormones.
Wrong working
Progesterone causes proliferation of the endometrium.
Right working
Oestrogen: regeneration (proliferation). Progesterone: maintenance.
Do this: Use 'regenerate' for the follicular phase, 'maintain' for the luteal phase.
Usually costs: ½-1 mark.
Mistake: Treating a missed period as proof of pregnancy
Over-simplified reasoning.
Wrong working
Absence of menstruation means she is pregnant.
Right working
It may indicate pregnancy but can also be due to stress or poor health.
Do this: Use 'may indicate'.
Usually costs: 1 mark in case-based items.

Exam tips

Learn the cycle as a four-row table: days, ovary, hormones, uterus. Most questions read straight off it.
When you see a graph, first find the tall narrow peak at mid-cycle: that is LH.
Say 'Graafian follicle' for the mature follicle and 'corpus luteum' for what remains after ovulation.
Use the alternative names (proliferative, secretory) only alongside the main names.
Mention that the cycle stops during pregnancy whenever a question involves fertilisation.

Practice questions on Menstrual Cycle and Its Hormonal Control

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Formation of the Graafian follicle during the follicular phase is stimulated mainly by:
(a) progesterone (b) FSH and LH (c) relaxin (d) hCG
Hint
Pituitary gonadotropins.
Answer
(b) FSH and LH.
Q2 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Menstruation does not occur during pregnancy.
Reason (R): During pregnancy the corpus luteum continues to secrete progesterone, which maintains the endometrium.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
Why does the lining stay?
Answer
(a).
Q3 · 2 marks · Very short answerBoard level
Define menarche and menopause. Between which two events does the normal reproductive phase of a woman lie?
Hint
First and last menstruation.
Answer
Menarche: the first menstruation at puberty. Menopause: the stopping of menstrual cycles at around 50 years. The reproductive phase lies between menarche and menopause.
Q4 · 4 marks · Case-basedHarder board level
Read and answer.
Suppose a graph of ovarian hormones over 28 days shows hormone X rising from day 6 to a peak at day 12-13, then falling, with a smaller rise later; and hormone Y staying low until day 14 and then rising to a high level until about day 25.
(a) Identify X and Y and their sources. (1)
(b) What is happening to the endometrium while X rises? (1)
(c) Why does Y fall at the end of a cycle without fertilisation, and what is the consequence? (2)
Hint
Peak before ovulation vs high after ovulation.
Answer
(a) X = oestrogen, from the growing ovarian follicles; Y = progesterone, from the corpus luteum. (b) The endometrium regenerates by proliferation. (c) Without fertilisation the corpus luteum degenerates, so progesterone falls; the endometrium breaks down and menstruation begins a new cycle.
Q5 · 3 marks · Short answerHOTS / competency
Suppose a woman is given a drug that blocks LH release from the pituitary around mid-cycle. Predict the effect on (a) ovulation, (b) corpus luteum formation, (c) her chance of conceiving in that cycle. Explain.
Hint
What does the LH surge do?
Answer
(a) No LH surge, so the Graafian follicle does not rupture: no ovulation. (b) The corpus luteum forms from the ruptured follicle, so it will not form (or progesterone stays low). (c) No ovum is released, so she cannot conceive in that cycle.
Q6 · 3 marks · Short answerHarder board level
Give the ovarian event, hormone and uterine change in the follicular phase and in the luteal phase.
Hint
Three things for each phase.
Answer
Follicular: primary follicles grow into a Graafian follicle; FSH and LH rise, follicles secrete oestrogen; endometrium regenerates (proliferates). Luteal: Graafian follicle becomes the corpus luteum; it secretes progesterone; the endometrium is maintained and becomes ready for implantation.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.How long does menstrual flow last?Show answer
3-5 days.
2.What causes ovulation?Show answer
The LH surge.
3.What does the corpus luteum secrete?Show answer
Large amounts of progesterone.
4.Which hormone rises during the follicular phase from the growing follicles?Show answer
Oestrogen.
5.What is menarche?Show answer
The first menstruation at puberty.
6.Around which day does ovulation occur in a 28-day cycle?Show answer
Day 14.

Menstrual Cycle and Its Hormonal Control: frequently asked questions

What are the phases of the menstrual cycle?

Menstrual phase, follicular (proliferative) phase, ovulatory phase and luteal (secretory) phase.

What is the LH surge?

The rapid rise of LH to its maximum level at mid-cycle, which makes the Graafian follicle rupture and release the ovum.

What is the role of progesterone in the menstrual cycle?

Progesterone from the corpus luteum maintains the endometrium so that it is ready for implantation of a fertilised ovum.

Why does menstruation stop during pregnancy?

The corpus luteum keeps secreting progesterone, so the endometrium is maintained and all events of the cycle stop.

Which animals have a menstrual cycle?

Female primates: monkeys, apes and humans.