7.4–7.5Hormones in human reproduction
During puberty reproductive hormones cause secondary sex characteristics to develop.
Oestrogen is the main female reproductive hormone, produced in the ovary. At puberty eggs begin to mature and one is released approximately every 28 days — this is called ovulation.
Testosterone is the main male reproductive hormone, produced by the testes, and it stimulates sperm production.
Higher tier only: you should be able to explain how the four interact. FSH from the pituitary causes an egg to mature and stimulates the ovaries to produce oestrogen. Oestrogen builds the uterus lining and inhibits further FSH, while stimulating the release of LH. The LH surge triggers ovulation around day 14. Progesterone then maintains the lining and inhibits both FSH and LH, so no further eggs mature; when progesterone falls, the lining breaks down and the cycle begins again.
Reading a hormone graph: the LH spike marks ovulation, oestrogen peaks just before it, and progesterone rises after it. Find ovulation first and the rest follows.
Worked exampleHigher tier only
Using the graph above: state the day of ovulation and give the evidence, then explain what progesterone is doing after it.
- Find the sharpest peak. LH spikes on day 14, far above its level on any other day.
- LH stimulates the release of the egg, so ovulation is on day 14.
- Check what oestrogen does just before: it peaks on day 13, the day before the LH spike — oestrogen stimulates the release of LH.
- Read progesterone after day 14: it rises from 3 to a peak of 9 around day 20, then falls back to 2 by day 28.
Answer: Ovulation is on day 14, shown by the LH spike. Progesterone rises after ovulation to maintain the uterus lining, and its fall at the end of the cycle is what causes the lining to break down and the next cycle to begin.
Common mistake
FSH and LH are made in the pituitary gland, not the ovary — the ovary makes oestrogen and progesterone. Getting the gland wrong loses marks in a question that otherwise describes the cycle correctly.
- Ovulation
- the release of a mature egg from the ovary, approximately every 28 days
- Oestrogen
- the main female reproductive hormone, produced in the ovary, which builds the uterus lining and inhibits FSH while stimulating the release of LH
- Testosterone
- the main male reproductive hormone, produced by the testes, which stimulates sperm production
- FSH
- follicle stimulating hormone, released by the pituitary, which causes an egg to mature and stimulates the ovaries to produce oestrogen
- LH
- luteinising hormone, released by the pituitary, whose surge triggers ovulation around day 14 of the cycle
- Progesterone
- the hormone that maintains the uterus lining and inhibits both FSH and LH; when it falls, the lining breaks down and the cycle begins again
7.6–7.7Contraception
Fertility can be controlled by hormonal and non-hormonal methods, and you should be able to evaluate them. The distinction the exam wants is which ones use hormones and which physically stop the sperm and egg meeting.
An evaluation weighs the evidence — how reliable each method is — against its implications, and the specification names four kinds: personal, social, economic and environmental. Condoms are the only method in the list that also protects against sexually transmitted infections, which is often the deciding point.
This is also a place where science does not settle the question. Whether a method is acceptable depends on religious belief, on a person's health and circumstances, and on whether they want children later. Science can say how reliable a method is; it cannot say which one a person should choose. Saying that explicitly, and then reaching a decision based on the evidence and the arguments, is what these questions are looking for.
7.8The use of hormones to treat infertilityHigher tier
Higher tier only
Hormones are used in modern reproductive technologies to treat infertility. The simplest version is giving FSH and LH in a 'fertility drug' to a woman, after which she may become pregnant in the normal way.
In Vitro Fertilisation (IVF) goes further, and the four steps are worth learning in order:
1. The mother is given FSH and LH to stimulate the maturation of several eggs. 2. The eggs are collected from the mother and fertilised by sperm from the father in the laboratory. 3. The fertilised eggs develop into embryos. 4. At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother's uterus.
Although fertility treatment gives a woman the chance to have a baby of her own, the specification is direct about the drawbacks: it is very emotionally and physically stressful, the success rates are not high, and it can lead to multiple births, which are a risk to both the babies and the mother.
Evaluate it from both perspectives the exam names. For the patient: the chance of a child they could not otherwise have, against repeated stress, cost, and a real chance of failure. For the doctor: how much intervention is justified, at what odds, and the ethical question of what happens to embryos that are not used. Microscopy techniques had to develop before IVF was possible at all, which is a neat example of one science enabling another.
- In Vitro Fertilisation
- IVF: a fertility treatment in which the mother is given FSH and LH to mature several eggs, which are collected and fertilised by sperm in the laboratory, and one or two resulting embryos are inserted into the mother's uterus
Before you practise
- FSH matures an egg and stimulates oestrogen release; LH triggers ovulation; oestrogen and progesterone build and maintain the uterus lining.
- Oestrogen and progesterone both inhibit FSH, which is how hormonal contraception prevents an egg maturing.
- Hormonal methods are very effective but have side effects and give no protection against infection; barrier methods do protect but are less reliable in use.
- In IVF, FSH and LH mature several eggs, which are collected and fertilised in the laboratory before an embryo is transferred.
- Clomifene therapy works by causing more FSH and LH to be released, so an egg matures.
- An evaluation needs the emotional and physical costs and the success rate, not just the mechanism.