3.2.5Organism Level Systems

Hormones to Treat Infertility — OCR Gateway GCSE Combined Science A J250 - Biology Revision Notes & Topical Questions

5 min read 9 parts Lesson 9 of 13

📚 OCR Gateway GCSE Combined Science A J250 - Biology Hub / Topical Revision

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Part 1 of 7Causes of infertility

Infertility is the inability to conceive a child.

Causes of infertility

Causes in women include failure to ovulate because of low levels of FSH and LH, blocked oviducts, and conditions such as polycystic ovary syndrome.

In men, causes include low sperm counts or sperm that move poorly.

Hormones can help some of these problems, and other treatments are used when hormones will not work.

Part 2 of 7Fertility drugs

Women who do not ovulate regularly can be given a fertility drug containing FSH and LH.

FSH stimulates the maturation of follicles, and LH stimulates ovulation.

A dose can be adjusted and timed so that eggs mature and are released, allowing natural conception.

Clomifene is another drug that blocks oestrogen feedback so more FSH is released.

A risk is that more than one egg may be released, increasing the likelihood of twins or triplets, which raises the risk of premature birth.

Part 3 of 7IVF: in vitro fertilisation

IVF is used when the oviducts are blocked, when sperm count is low or when drugs do not work. Fertilisation takes place outside the body.

The woman takes FSH and LH to stimulate several eggs to mature at the same time.

The eggs are collected from the ovary.

The eggs are mixed with sperm from the father (or a donor) in a dish in the laboratory, where fertilisation takes place.

The fertilised eggs develop into embryos, which are monitored for several days.

One or two healthy embryos are transferred into the uterus, where they may implant. Other embryos may be frozen for later use.

The woman is given progesterone to help maintain the lining of the uterus.

Part 4 of 7Evaluation: success, risks and ethics

Advantages	Disadvantages
Enables people who cannot conceive naturally to have a child	Success rate is low; on average only about a quarter of cycles in younger women produce a baby, and less with age
Can be done when the oviducts are blocked	Emotionally and physically stressful, and costly
Embryos can be screened for serious genetic disease	High doses of hormones can cause side effects such as mood swings and overstimulation of the ovaries
Spare embryos can be stored	Multiple births carry risks for mother and babies

Ethical issues include what should be done with unused embryos (destruction, donation to research or storage), the fact that some people believe embryos should be protected, and whether the state should pay for treatment. Older women have lower success rates, and some argue that resources should be limited by age.

Part 5 of 7Interpreting data

Data tables might give the percentage of IVF cycles leading to a live birth for different age groups.

Interpreting data

Describe the trend (for example, success falls from about 32% in women under 35 to about 5% in those over 42),

then link it to the biology: egg quality and the number of follicles decline with age.

Success rate must be calculated as number of births divided by number of cycles x 100.

Because treatment is expensive and rates are low, a balanced conclusion must weigh the cost, the physical effects and the potential benefit to the couple.

Part 6 of 7Other approaches and choosing treatments

Hormones are only one approach to infertility.

Intracytoplasmic sperm injection (ICSI) injects a single sperm into an egg and is used when the sperm count is very low.

Donor eggs or sperm can be used if one partner cannot produce healthy gametes.

Surgery may unblock the oviducts.

Lifestyle changes help too: being very underweight or overweight can disturb the hormone balance and stop ovulation,

and smoking and alcohol reduce fertility in both sexes.

Doctors therefore consider the cause before deciding on treatment: FSH and LH for ovulation problems, IVF for blocked tubes, ICSI for sperm problems.

In evaluation questions, give a balanced argument and a conclusion.

Other approaches and choosing treatments

A good response says that IVF has helped millions of couples but has a low success rate for older women, costs a lot,

and involves ethical issues about embryos.

It also notes that decisions about funding are made by society and not just by scientists.

Always refer to the information in the question,

such as the age group or the success percentages,
and make comparisons using figures rather than general words like "good" or "bad".

Part 7 of 7Exam-style questions

Explain how FSH can be used to treat a woman who does not ovulate. [3]3 marks
A clinic carried out 400 IVF cycles and 96 led to a live birth. Calculate the success rate. [2]2 marks
Give two disadvantages of IVF. [2]2 marks

Key terms

Term	Meaning
Infertility	Inability to conceive a child.
IVF	In vitro fertilisation; eggs are fertilised outside the body.
Fertility drug	A hormone-based treatment that stimulates ovulation.
Embryo	An early stage of development after fertilisation.
Follicle	A structure in the ovary containing a developing egg.
Ethical issue	A moral question that has no purely scientific answer.

Avoid these mistakes

Saying that IVF is performed inside the body; fertilisation is outside the body.

Writing that FSH causes ovulation; LH does.

Forgetting to mention that fertility drugs can cause multiple births.

Giving ethical points without explaining them, such as simply "it is wrong".

Calculating success per embryo rather than per cycle when the question says per cycle.

Last updated: 20 October 2026