Reproductive hormones (AQA GCSE Biology Combined Science): Revision Notes
Reproductive hormones
What are reproductive hormones?
Reproductive hormones are special chemicals that control how our bodies develop and reproduce. They manage important processes like puberty, the menstrual cycle, and making sperm or eggs.
These hormones act as chemical messengers, travelling through the bloodstream to target organs where they trigger specific biological responses.
The menstrual cycle
The menstrual cycle happens in women between puberty and around age 50. It repeats every 28 days on average.
What happens during the cycle:
- Menstruation (days 1-5): The lining of the womb breaks down and leaves the body
- Building up (days 6-13): The womb lining starts to thicken again
- Ovulation (around day 14): An egg is released from the ovary
- Waiting period (days 15-28): The womb lining stays thick, ready for a baby
Key timing:
- Days 14-16 are when pregnancy is most likely to happen
- The cycle takes about 28 days to complete
The four main hormones
FSH (Follicle-stimulating hormone)
- What it does: Makes eggs in the ovaries grow and mature
- When it works: Early in the cycle
LH (Luteinising hormone)
- What it does: Triggers ovulation - the release of a mature egg
- When it works: Around day 14
Oestrogen
- What it does: Helps build up the womb lining
- When it works: Throughout the cycle, especially after menstruation
- At puberty: Causes breast development and starts the menstrual cycle
Progesterone
- What it does: Maintains the womb lining and keeps it thick
- When it works: After ovulation, in the second half of the cycle
Each hormone has a specific role and timing, working in a carefully coordinated sequence to control the reproductive cycle.
Male reproductive hormone
Testosterone
- What it does: Controls sperm production in men
- At puberty it causes:
- Growth of testes and penis
- Voice breaking and getting deeper
- Facial and body hair growth
- Growth spurts
How the hormones work together
The four hormones work like a coordinated team to control reproduction:
- FSH starts the process by helping eggs mature
- LH triggers ovulation when the egg is ready
- Oestrogen and progesterone prepare and maintain the womb lining
- If no baby develops, the cycle starts again
This hormonal coordination ensures that the body is properly prepared for potential pregnancy at the right time in the cycle.
Key Points to Remember:
- Four key female hormones: FSH, LH, oestrogen, and progesterone control the menstrual cycle
- Testosterone is the main male hormone that controls sperm production and puberty changes
- The menstrual cycle lasts about 28 days with ovulation around day 14
- All hormones work together to control reproduction and development
- Puberty changes happen because of these hormones becoming active