Reproductive Hormones and the Menstrual CycleAQA GCSE Biology: Revision notes
Section 1
Puberty and Reproductive Hormones
During puberty, reproductive hormones are released that cause secondary sex characteristics to develop, such as breast development in females and facial hair growth in males. These hormones also control the menstrual cycle in females and sperm production in males. Hormonal effects act more slowly than nervous responses but last much longer.
Section 2
Sex Hormones: Oestrogen and Testosterone
- Oestrogen is the main female reproductive hormone, produced in the ovary. From puberty, eggs begin to mature in the ovaries, and one is released approximately every 28 days — this release is called ovulation
- Testosterone is the main male reproductive hormone, produced by the testes. It stimulates sperm production
Section 3
The Menstrual Cycle Hormones
The menstrual cycle is controlled by four hormones working together:
| Hormone | Made by | Main role |
|---|---|---|
| FSH (follicle stimulating hormone) | Pituitary gland | Causes an egg to mature in the ovary |
| LH (luteinising hormone) | Pituitary gland | Stimulates the release of the mature egg (ovulation) |
| Oestrogen | Ovary | Helps build and maintain the uterus lining |
| Progesterone | Ovary | Maintains the uterus lining |
Section 4
How the Cycle Is Controlled (Higher Tier)
FSH, oestrogen, LH and progesterone interact in a coordinated cycle:
- FSH causes an egg to mature and stimulates the ovary to release oestrogen
- Rising oestrogen stimulates the release of LH and builds up the uterus lining
- A surge in LH triggers ovulation
- After ovulation, progesterone (and some oestrogen) maintains the uterus lining ready for a fertilised egg
- If no fertilised egg implants, progesterone and oestrogen levels fall, the uterus lining breaks down (menstruation), and FSH begins to rise again to start a new cycle
You do not need to remember exact day numbers of the cycle — focus on the order in which each hormone rises and what it triggers.
Section 5
Contraception and Fertility Treatment
Hormonal and non-hormonal methods can be used to prevent pregnancy:
- Hormonal: oral contraceptive pill (inhibits FSH production so no eggs mature); contraceptive injection, implant or skin patch (slow-release progesterone)
- Non-hormonal: condoms and diaphragms; intrauterine devices (IUDs); spermicidal agents; abstaining from intercourse; surgical sterilisation
Reproductive hormones can also be used to treat infertility (HT):
- FSH and LH can be given as a 'fertility drug' to stimulate egg maturation and release
- In IVF (in vitro fertilisation), FSH and LH are given to stimulate the maturation of several eggs, which are collected and fertilised in a laboratory; the resulting embryos are inserted into the mother's uterus
- IVF raises emotional, physical and ethical issues (e.g. multiple births, cost, and views on embryo use) that should be evaluated
Don't confuse FSH's role in contraception (the pill suppresses it) with its role in fertility treatment (given as a drug to stimulate it) — same hormone, opposite goals.
Must Know
- Puberty hormones trigger secondary sex characteristics
- Oestrogen (ovary) and testosterone (testes) are the main female and male reproductive hormones
- FSH matures an egg; LH triggers its release (ovulation); oestrogen and progesterone maintain the uterus lining
- FSH, oestrogen, LH and progesterone interact across the cycle in a set order (HT)
- Contraception can be hormonal (pill, injection, implant, patch) or non-hormonal (barrier methods, IUD, sterilisation, abstinence)
- IVF uses FSH and LH to stimulate egg production for fertilisation outside the body (HT)
That's the notes covered.
Carry on to the next subtopic.