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5.3.3Homeostasis and Response

The Uses of Hormones to Treat Infertility

5 min read 9 parts Lesson 10 of 11 Unit quiz

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Section 1 of 9Causes of infertility

Infertility is the inability to conceive a child.

Causes of infertility
It can have many causes, such as blocked oviducts, low sperm count or a lack of the hormones needed to release eggs.
In some women the pituitary gland does not produce enough FSH, so eggs do not mature, and ovulation does not occur.
Treatment can use hormones to correct the problem or help fertilisation take place outside the body.

Section 2 of 9Fertility drugs

A woman who is not ovulating can be given a course of hormones.

FSH and LH
FSH and LH given by injection stimulate the maturation of eggs in the ovary and cause ovulation.
Other drugs such as clomifene encourage the pituitary to release more FSH.

Once a follicle has developed, the woman can try to conceive naturally. Sometimes more than one egg matures, increasing the chance of multiple births (twins or triplets). It is not guaranteed to work and the treatment may need repeating.

Section 3 of 9In vitro fertilisation (IVF)

In IVF eggs are fertilised outside the body, in a laboratory dish.

FSH and LH
The woman is given FSH and LH to stimulate the maturation of several eggs, instead of the usual one.
The eggs are collected from the ovary.
The eggs are mixed with sperm from the father in the laboratory so that fertilisation occurs.
The fertilised eggs develop into embryos.
One or two embryos are inserted into the woman's uterus.
If an embryo implants in the lining, a pregnancy develops.

Embryos that are not used may be frozen or destroyed, or donated to research. Embryos can also be checked for genetic disorders before they are implanted.

Section 4 of 9Evaluating IVF

BenefitsDrawbacks
Allows couples who cannot conceive naturally to have a childSuccess rate is low, around 30 percent or less per cycle, and falls with age
Embryos can be screened for serious genetic conditionsEmotionally stressful and often physically demanding for the woman
Fertility drugs can help with a range of causesExpensive, with many couples paying privately
Risk of multiple births, which can be harmful to the mother and babies

There are also ethical questions

  • the production of spare embryos, who should be offered treatment, and whether embryos should be selected on the basis of their genes.
  • Different people have different views, which is why evaluation questions need balanced answers.

Section 5 of 9Applying the idea and links

A calculation might state that 3000 IVF cycles resulted in 750 births, giving 25 percent success.

Applying the idea and links
When asked why IVF might have a higher success rate in younger women, the answer is that the quality and number of eggs fall with age.
Link this topic to the hormones of the menstrual cycle (5.3.1),
  • because the treatment copies the natural FSH and LH surge, and to the use of contraception (5.3.2),
  • which uses hormones for the opposite aim of preventing ovulation.

Remember that the use of hormones in the body works through negative feedback, so treatment must be carefully controlled to avoid overstimulation of the ovaries.

Success rates are reported as the percentage of treatment cycles that lead to a live birth.

Applying the idea and links
A typical figure falls from about 35 percent in women under 35 to under 10 percent in women over 40, because egg quality and number decline with age.
Because the hormone doses given to stimulate the ovaries can cause ovarian hyperstimulation, with painful swelling, doctors monitor the response with blood tests and ultrasound scans.
Women are offered counselling because the treatment can be emotionally demanding, and a failed cycle can be distressing.

Compared with natural fertilisation, IVF also gives scientists a chance to study early embryo development, which has led to improved understanding of why some pregnancies fail.

Section 6 of 9The ethics debate in more detail

IVF creates more embryos than are used.

The ethics debate in more detail
Some people feel an embryo is a human life from fertilisation,
  • so destroying spare embryos is wrong;
    • others argue that an early embryo is a tiny ball of cells with no feeling and that the benefits to families outweigh this.
Screening embryos for a genetic disease helps to avoid suffering,
  • but selecting embryos for characteristics such as sex raises worries about 'designer babies'.
Costs raise fairness questions about who gets funding, and the age limit for treatment is debated.

For the exam, give a point with reasoning for each side and, if asked for an opinion, make a clear choice supported by evidence rather than just stating it.

Section 7 of 9Exam-style questions

  1. Describe how FSH and LH can be used to treat infertility. [3]3 marks

  2. Describe the main steps in IVF. [4]4 marks

  3. Evaluate the use of IVF. [3]3 marks

Section 8 of 9Key terms

TermMeaning
InfertilityInability to conceive a child.
IVFIn vitro fertilisation; fertilisation of eggs outside the body.
EmbryoEarly stage of development after fertilisation.
FSHHormone stimulating egg maturation.
LHHormone stimulating ovulation.
Multiple birthBirth of more than one baby from one pregnancy.
Fertility drugA hormone-based medicine that promotes ovulation.

Section 9 of 9Exam technique

1
Saying IVF takes place inside the body; in vitro means in glass, outside the body.
2
Confusing FSH function with LH
  • FSH matures eggs;
    • LH triggers ovulation.
3
Stating that IVF always succeeds.
4
Forgetting to give a balanced answer when asked to evaluate.
5
Saying fertility drugs are used to prevent pregnancy; they promote it.
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