# Hormones in Human Reproduction
Hormones control the changes during puberty, the menstrual cycle, and fertility. Understanding these processes and how they can be controlled is important for GCSE Biology.
1. Puberty Hormones
| Hormone | Produced By | Effects |
|---|---|---|
| Testosterone | Testes | Male secondary sexual characteristics (deepening voice, facial hair, muscle growth, sperm production) |
| Oestrogen | Ovaries | Female secondary sexual characteristics (breast development, widening hips, menstrual cycle begins) |
2. The Menstrual Cycle (28 days)
| Day | Event | Hormones |
|---|---|---|
| 1-5 | Menstruation (uterus lining sheds) | Low hormone levels |
| 6-13 | Uterus lining rebuilds | FSH (pituitary) → egg matures; Oestrogen (ovaries) → lining thickens |
| 14 | Ovulation (egg released) | LH surge (pituitary) triggers ovulation |
| 15-28 | Lining maintained | Progesterone (corpus luteum) maintains lining |
| 28 | If no fertilisation → progesterone drops → cycle restarts |
Hormone Interactions (Negative Feedback)
- FSH stimulates egg development and oestrogen production
- Oestrogen inhibits FSH and stimulates LH
- LH triggers ovulation
- Progesterone maintains lining and inhibits FSH and LH
3. Contraception
Hormonal Methods
| Method | How It Works |
|---|---|
| Combined pill | Oestrogen + progesterone; inhibits FSH → no egg maturation |
| Progesterone-only pill | Thickens cervical mucus |
| Implant/injection | Slow release of progesterone |
| IUS (hormonal coil) | Releases progesterone locally |
Non-Hormonal Methods
| Method | How It Works |
|---|---|
| Condoms | Barrier; also prevents STIs |
| Diaphragm | Barrier over cervix |
| IUD (copper coil) | Prevents implantation |
| Spermicide | Kills sperm |
| Surgical sterilisation | Permanent; cut/block tubes |
| Abstinence | No sexual intercourse |
4. Fertility Treatments
Clomifene Therapy
- Drug that stimulates ovulation (by stimulating FSH/LH production)
- Used when women don't ovulate regularly
IVF (In Vitro Fertilisation)
- FSH and LH injections → stimulate multiple egg production
- Eggs collected surgically
- Fertilised with sperm in laboratory
- Embryos develop to small ball of cells
- 1-2 embryos implanted into uterus
IVF Issues
- Emotionally and physically stressful
- Low success rate (~25-30%)
- Multiple births risk
- Ethical concerns about unused embryos
- Expensive
5. Practice Questions
- Name the four hormones involved in the menstrual cycle.
- What triggers ovulation?
- How does the combined contraceptive pill prevent pregnancy?
- Describe the steps of IVF.
- Why might some people object to IVF on ethical grounds?
Want to check your answers and get step-by-step solutions?
Summary
- Puberty: testosterone (males), oestrogen (females)
- Menstrual cycle: FSH → oestrogen → LH → progesterone (28-day cycle)
- Contraception: hormonal (pill, implant) or barrier (condom, diaphragm)
- IVF: FSH/LH stimulation → egg collection → fertilisation → embryo transfer