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/sperm production: • In males, the main reproductive hormone is **testosterone**, produced by the **testes**; it stimulates sperm production. • In females, the main reproductive hormone is **oestrogen**, produced by the **ovaries**; it also drives the menstrual cycle.

Name the main hormone

What is the main reproductive hormone in males, and where is it made?

• Testosterone, made in the testes
• Oestrogen, made in the testes
• Testosterone, made in the ovaries
• Insulin, made in the pancreas

The menstrual cycle 🌸

The roughly **28-day** cycle is run by four hormones: • **FSH** (pituitary) — **matures an egg** and makes the ovaries release oestrogen. • **Oestrogen** (ovaries) — **builds up the uterus lining**. • **LH** (pituitary) — a surge **triggers ovulation** (egg release) at about **day 14**. • **Progesterone** (ovaries) — **maintains the lining**; when it falls, the lining breaks down (a period, ~day 1).

Run the cycle in order

An interactive activity.

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 — a favourite Higher-tier question: • **Oestrogen** inhibits **FSH** (so usually only one egg matures) and **stimulates** the release of **LH**. • **Progesterone** inhibits both **FSH** and **LH**, keeping the cycle paused while the lining is maintained. When progesterone falls, FSH is no longer inhibited, 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

Preventing pregnancy 🛡️

Contraception works in two broad ways: • **Hormonal** — the **pill**, **injection**, **implant** and **patch** use oestrogen and/or progesterone to inhibit **FSH** so no egg matures. • **Non-hormonal** — **barrier methods** (condom, diaphragm) stop sperm meeting the egg; plus the **IUD**, **spermicides**, **abstinence** (especially around ovulation) and surgical **sterilisation**. Only barrier methods also reduce the spread of sexually transmitted infections.

Which are hormonal?

Pick the TWO methods of contraception that work using hormones.

• The contraceptive pill
• A slow-release implant
• A condom
• Surgical sterilisation

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]

An interactive activity.

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).