Fertility Forum

Fertility Forum

At puberty, a flood of hormones reshapes the body and switches on a monthly cycle that can last for decades. The same hormones can be used to **prevent** pregnancy, or to **help** it happen. This module runs the whole reproductive control system. (The finer hormone interactions and IVF detail are **Higher tier**.)

The hormones of puberty

During puberty, reproductive hormones trigger the **secondary sexual characteristics** and start egg and sperm production. Each sex runs the same idea on a different hormone.

The menstrual cycle

The roughly **28-day** cycle is run by four hormones: two from the brain, two from the ovaries. Learn which gland makes each one, because that is half the marks.

Which gland makes what?

Run the cycle in order

Put the events of one menstrual cycle into the order they happen, starting from the first day.

• The uterus lining breaks down (menstruation)
• FSH matures an egg in the ovary
• Oestrogen builds up the uterus lining
• An LH surge triggers ovulation (~day 14)
• Progesterone maintains the uterus lining
• Progesterone falls, so the lining breaks down again

What triggers ovulation?

Around day 14 of the cycle, which hormone surges to trigger the release of an egg?

• LH
• FSH
• Progesterone
• Testosterone

How the hormones interact [Higher tier]

The four hormones control each other by feedback, and this is a favourite Higher-tier question. Oestrogen _____ FSH, which is why usually only one egg matures. Oestrogen also _____ the release of LH. Progesterone inhibits both FSH and LH, holding the cycle still while the _____ is maintained. When progesterone _____, FSH is no longer held back, so the next cycle can begin.

Why the pill works [Higher tier]

The combined contraceptive pill contains oestrogen and progesterone. How does keeping these hormones high prevent pregnancy?

• They inhibit FSH, so no egg matures
• They boost FSH, so many eggs mature
• They trigger constant ovulation
• They stop the testes making sperm

How each method works

Helping fertility: IVF [Higher tier]

When a couple can't conceive naturally, **IVF** (in-vitro fertilisation) can help: **FSH** and **LH** are given to stimulate several eggs to mature; the eggs are collected and **fertilised by sperm in the lab**; the fertilised eggs grow into tiny embryos, and **one or two** are inserted into the uterus. A balanced view: IVF gives many couples a baby, **but** success rates are fairly low, it is emotionally and physically stressful, it is expensive, and it can lead to risky **multiple births**.

Walk through IVF [Higher tier]

A couple cannot conceive because eggs are not being released. Work through their IVF treatment.

• What is given first to help produce eggs?
• Several eggs have been collected. What happens to them next?
• The fertilised eggs have grown into tiny embryos. How many are inserted into the uterus?

Write the balanced answer [Higher tier]

"IVF should be available free to everyone who wants it." Evaluate this claim in about 60 words. A balanced answer needs all three of:

• one clear benefit of IVF for couples who cannot conceive naturally
• two drawbacks, chosen from success rate, cost, physical and emotional stress, or the risk of multiple births
• a conclusion that actually comes down on one side

In the exam

Forum closed. Grade-9 habits for human reproduction: • Sequence the cycle: **FSH** matures the egg, **oestrogen** builds the lining + triggers an **LH** surge, **LH** causes ovulation, **progesterone** maintains the lining. • **[HT]** Describe the interactions: oestrogen **inhibits FSH** + **stimulates LH**; progesterone **inhibits FSH and LH**: that is how the pill works. • **IVF**: always give a **balanced** answer. Benefit (a pregnancy) vs drawbacks (low success rate, multiple births, stress, cost).