What are the main sexual hormones in humans and their functions?

The main sexual hormones in humans are testosterone, estrogen, and progesterone. Testosterone, primarily found in males, is responsible for the development of male secondary sexual characteristics and sperm production. Estrogen, primarily found in females, regulates the menstrual cycle and is crucial for the development of female secondary sexual characteristics. Progesterone, also found in females, plays a key role in regulating the menstrual cycle and maintaining pregnancy.

How do sexual hormones influence puberty in humans?

During puberty, sexual hormones trigger the development of secondary sexual characteristics. In males, increased levels of testosterone lead to the growth of facial and body hair, deepening of the voice, and muscle growth. In females, estrogen promotes breast development, the widening of hips, and the start of the menstrual cycle. These changes are essential for reproductive maturity and are a key focus in the Cambridge IGCSE Biology curriculum.

What role do sexual hormones play in the menstrual cycle?

Sexual hormones such as estrogen and progesterone play crucial roles in regulating the menstrual cycle. Estrogen helps to rebuild the uterine lining after menstruation, while progesterone prepares the uterus for a potential pregnancy by maintaining the lining. If pregnancy does not occur, levels of these hormones drop, leading to menstruation. Understanding this cycle is important for students studying human reproduction in Cambridge IGCSE Biology.

How do contraceptive methods utilize sexual hormones?

Many contraceptive methods, such as birth control pills, use synthetic forms of estrogen and progesterone to prevent pregnancy. These hormones work by inhibiting ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining to prevent implantation. This application of sexual hormones is an important aspect of human reproduction studies in the Cambridge IGCSE Biology curriculum.

What are the effects of hormonal imbalances on human reproduction?

Hormonal imbalances can significantly affect human reproduction. In females, imbalances in estrogen and progesterone can lead to irregular menstrual cycles, infertility, or conditions like polycystic ovary syndrome (PCOS). In males, low levels of testosterone can result in reduced sperm production and fertility issues. Understanding these effects is crucial for students studying sexual hormones in the context of human reproduction in Cambridge IGCSE Biology.

Why is "Saying both sexes have testosterone and oestrogen equally." a common mistake in Sexual Hormones in Humans?

Why it happens: Both have small amounts. How to avoid it: Both sexes have BOTH hormones in small amounts, but: males have HIGH testosterone, low oestrogen; females the reverse. The DOMINANT hormone shapes secondary sexual characteristics.

Why is "Saying menstruation starts at ovulation." a common mistake in Sexual Hormones in Humans?

Why it happens: Both events are part of the cycle. How to avoid it: Menstruation = day 1 (lining breaks down). Ovulation = day 14. They're TWO different events two weeks apart.

Why is "Saying progesterone BUILDS the uterine lining." a common mistake in Sexual Hormones in Humans?

Why it happens: Both hormones affect the lining. How to avoid it: OESTROGEN BUILDS the lining (after menstruation). PROGESTERONE MAINTAINS it (after ovulation). Different jobs.

ReproductionCambridge IGCSE Biology (0610)

Sexual Hormones in Humans

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Sexual Hormones in Humans — Cambridge IGCSE 0610 Biology Extended (2026)

Hormones that drive puberty, the menstrual cycle and pregnancy. Three to know: testosterone, oestrogen, progesterone.

What you’ll learn

Mapped to the Cambridge IGCSE 0610 syllabus (2026-2028).

16.5 — Identify testosterone, oestrogen and progesterone and their sources.
16.5 — Describe secondary sexual characteristics.
16.5 — Describe the menstrual cycle and the role of each hormone.

Puberty — switching on the sex hormones

Testosterone (males) and oestrogen (females) drive the changes around age 10-14.

Puberty = the transition from child to adult, ~10-14 years old.

In males.

Brain triggers TESTES to release TESTOSTERONE.
Effects (secondary sexual characteristics):
- Voice DEEPENS (vocal cords grow).
- Facial + chest + pubic hair.
- Wider shoulders + muscle development.
- Penis + testes enlarge.
- Sperm production begins.

In females.

Brain triggers OVARIES to release OESTROGEN.
Effects:
- Breasts develop.
- Hips + pelvis widen (for childbirth).
- Pubic + underarm hair.
- Menstrual cycle begins (first period = menarche).
- Ovaries start releasing eggs.

Both sexes:

Growth spurt.
Sweat + sebaceous glands more active (acne, body odour).

Worked qualitative. Why do voices deepen for boys?

Testosterone causes vocal cords to lengthen + thicken.
Longer/thicker cords vibrate more slowly → lower pitch.
Larynx ('Adam's apple') grows visibly.
Voice 'breaks' as cords adjust over weeks/months.

Cambridge tip. Memorise 3-4 changes for each sex. Don't forget: BOTH have small amounts of the OTHER hormone (just in different proportions).

Testosterone: male puberty.
Oestrogen: female puberty.
Brain triggers gonads to release.
Both sexes growth spurt.

The menstrual cycle

28 days. Four stages: menstruation, repair, ovulation, lining maintained.

Why a cycle? Each month, the uterus prepares for a possible pregnancy. If no fertilisation occurs, the prepared lining is shed and rebuilt for next time.

The four stages (~28-day cycle):

Days 1-5 — MENSTRUATION.

Uterine lining (built up last cycle) BREAKS DOWN.
Bleeding through vagina = period.
Caused by FALL in oestrogen and progesterone.

Days 6-13 — REPAIR/PROLIFERATION.

Pituitary releases FSH → ovary → develops a follicle (egg + cells around it).
Follicle releases OESTROGEN.
Oestrogen REBUILDS uterine lining (proliferation).
Around day 14, oestrogen peak triggers LH from pituitary.

Day 14 — OVULATION.

LH surge triggers OVULATION — egg released from ovary.
Egg enters oviduct.
Most fertile day; conception more likely.

Days 15-28 — SECRETORY PHASE.

Empty follicle becomes CORPUS LUTEUM.
Corpus luteum produces PROGESTERONE.
Progesterone MAINTAINS uterine lining (thick, vascularised, ready for implantation).
Progesterone also INHIBITS new follicle development.

If no fertilisation:

Corpus luteum dies after ~14 days.
Progesterone drops sharply.
Lining can no longer be maintained → breaks down → menstruation → cycle restarts.

If fertilisation:

Embryo (after implantation) produces hCG (human chorionic gonadotropin).
hCG keeps corpus luteum alive → progesterone keeps coming.
Lining maintained → pregnancy continues.

Worked qualitative. Why are hormonal CONTRACEPTIVE PILLS designed to mimic pregnancy hormones?

The pill contains synthetic oestrogen + progesterone.
These trick the brain into thinking pregnancy is happening.
Brain stops releasing FSH/LH → no follicle development → no ovulation.
Without ovulation, no fertilisation possible → no pregnancy.
Stopping the pill: hormones drop → cycle resumes.

Cambridge tip. Memorise the FOUR stages and which hormone dominates each. Cambridge graphs the cycle and asks 'what's happening on day 14?' or 'which hormone is at peak?'.

1-5: menstruation (lining sheds).
6-13: repair (oestrogen rises).
14: ovulation (LH peak).
15-28: maintenance (progesterone).
No fertilisation → cycle restarts.

Roles of the four hormones

Each has a specific job at a specific time.

FSH (follicle-stimulating hormone) — from PITUITARY.

Stimulates follicle development in ovary.
Stimulates ovary to make oestrogen.

Oestrogen — from OVARY (developing follicle).

Repairs and thickens uterine lining.
Inhibits FSH (negative feedback).
Triggers LH surge (positive feedback).
Drives female secondary sexual characteristics.

LH (luteinising hormone) — from PITUITARY.

Triggers ovulation around day 14.
Forms corpus luteum from empty follicle.

Progesterone — from OVARY (corpus luteum).

Maintains uterine lining.
Inhibits FSH and LH (no new follicles develop).
Falling levels (if no pregnancy) trigger menstruation.

Worked qualitative. Why do women on hormonal contraception still have 'periods'?

Most pills give 21 days of hormones + 7 'placebo' days.
During placebo days, hormone levels drop → lining sheds → bleeding occurs.
This is called withdrawal bleeding, not a true menstrual period (no ovulation).
Newer methods (continuous pill, implant) skip this entirely.

Cambridge tip. Cambridge often shows hormone levels graph. Memorise: oestrogen rises in days 6-14, progesterone rises in days 15-28.

FSH: starts follicle.
Oestrogen: builds lining + triggers LH.
LH: triggers ovulation.
Progesterone: maintains lining.

How it’s examined

Sexual hormones appear Paper 4 (5-10 marks: identify hormone, describe cycle, hormone graphs). Examiner reports flag students confusing oestrogen with progesterone roles, and missing day 14 ovulation.

Sources: Cambridge IGCSE Biology 0610 syllabus 2026-2028 (16.5); 0610/42 Oct/Nov 2024 — Q15 (sex hormones); 0610 Examiner Reports 2022-2024. Last reviewed 2026-05-07.

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Step-by-step worked examples — Sexual Hormones in Humans

Step-by-step solutions to past-paper-style questions on sexual hormones in humans, written exactly the way a tutor would explain them at the board.

1Hormones at puberty
Core• puberty
Question
Name the SEX HORMONES that drive puberty in males and females. Give TWO secondary sexual characteristics each.
Step-by-step solution
1. Step 1
  Males: TESTOSTERONE from testes.
2. Step 2
  Effects: voice deepens, facial + body hair, broader shoulders + muscles, sperm production, testes + penis enlarge.
3. Step 3
  Females: OESTROGEN from ovaries.
4. Step 4
  Effects: breasts develop, pelvis widens, body hair, menstrual cycle starts, ovaries release eggs.
Answer
Males: testosterone → deeper voice, facial hair, muscle, sperm. Females: oestrogen → breasts, wider pelvis, periods.
2The menstrual cycle
Extended• Adapted from 0610/42 Oct/Nov 2024 Q15• menstrual cycle
Question
Describe the four stages of the menstrual cycle (~28 days).
Step-by-step solution
1. Step 1
  Days 1-5: MENSTRUATION. Uterus lining (endometrium) breaks down → vaginal bleeding (period). No fertilisation last cycle.
2. Step 2
  Days 6-13: REPAIR. Lining starts to thicken again. OESTROGEN levels rising.
3. Step 3
  Day 14: OVULATION. Egg released from ovary → enters oviduct. Most fertile time.
4. Step 4
  Days 15-28: LINING MAINTAINED. PROGESTERONE keeps the lining thick, ready for implantation. If no fertilisation, progesterone falls → cycle restarts.
Answer
1-5: menstruation. 6-13: repair (oestrogen rises). 14: ovulation. 15-28: lining maintained (progesterone). If no fertilisation: cycle repeats.
Examiner tip
Cambridge marks the FOUR stages and the role of each hormone. Memorise the days.
3Roles of OESTROGEN and PROGESTERONE
Extended• female hormones
Question
Distinguish the roles of OESTROGEN and PROGESTERONE in the menstrual cycle.
Step-by-step solution
1. Step 1
  Oestrogen (made by ovaries — by developing follicle):
2. Step 2
  REPAIRS and BUILDS UP uterus lining after menstruation. Triggers OVULATION (around day 14).
3. Step 3
  Progesterone (made by corpus luteum after ovulation):
4. Step 4
  MAINTAINS the thick uterus lining ready for implantation. Inhibits release of new eggs. If no pregnancy, levels fall → menstruation begins.
Answer
Oestrogen builds lining + triggers ovulation. Progesterone maintains lining and prevents new eggs.

Key Definitions and Keywords — Sexual Hormones in Humans

Definitions to memorise and the exact keywords mark schemes credit for sexual hormones in humans answers — sharpened from recent examiner reports for the 2026 0610 sitting.

Testosterone
Examiner keyword
Male sex hormone from the testes. Drives male puberty (voice, body hair, muscle) and sperm production.
Oestrogen
Examiner keyword
Female sex hormone from the ovaries. Drives female puberty (breasts, pelvis, body hair). Triggers ovulation; rebuilds uterine lining.
Progesterone
Examiner keyword
Hormone from the ovary (corpus luteum) AFTER ovulation. MAINTAINS the thick uterine lining; inhibits release of new eggs.
Menstruation
Breakdown and removal of the uterine lining (endometrium) at the start of each cycle. Visible as menstrual bleeding (a period).
Ovulation
Release of a mature egg from an ovary into the oviduct. Around day 14 of a 28-day cycle.

Common Mistakes and Misconceptions — Sexual Hormones in Humans

The traps other students keep falling into on sexual hormones in humans questions — taken from recent Cambridge IGCSE 0610 examiner reports and mark schemes — and how to avoid them.

✕Saying both sexes have testosterone and oestrogen equally.
Why it happens
Both have small amounts.
How to avoid it
Both sexes have BOTH hormones in small amounts, but: males have HIGH testosterone, low oestrogen; females the reverse. The DOMINANT hormone shapes secondary sexual characteristics.
✕Saying menstruation starts at ovulation.
Why it happens
Both events are part of the cycle.
How to avoid it
Menstruation = day 1 (lining breaks down). Ovulation = day 14. They're TWO different events two weeks apart.
✕Saying progesterone BUILDS the uterine lining.
Why it happens
Both hormones affect the lining.
How to avoid it
OESTROGEN BUILDS the lining (after menstruation). PROGESTERONE MAINTAINS it (after ovulation). Different jobs.

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Sexual Hormones in Humans

Short Study Notes in the form of Slides

Detailed Study Notes

What you’ll learn

How it’s examined

1Hormones at puberty

2The menstrual cycle

3Roles of OESTROGEN and PROGESTERONE

Testosterone

Oestrogen

Progesterone

Menstruation

Ovulation

✕Saying both sexes have testosterone and oestrogen equally.

✕Saying menstruation starts at ovulation.

✕Saying progesterone BUILDS the uterine lining.

Practice questions

Past paper style quiz

Assess your understanding

Video lesson

Sexual Hormones in Humans — frequently asked questions