Hormonal coordination: the menstrual cycle and contraception
Biology · GCSE · The School
Four hormones, four jobs
FSH (follicle-stimulating hormone) causes an egg to mature in the ovary. OESTROGEN, released as the egg matures, repairs and thickens the uterus lining and triggers LH. LH (luteinising hormone) triggers ovulation, the release of the egg. PROGESTERONE maintains the uterus lining after ovulation, and falls if no pregnancy occurs, causing the lining to break down.
The cycle, stage by stage
Roughly a 28-day cycle. DAYS 1-4: the uterus lining breaks down (menstruation) as progesterone falls. DAYS 5-13: FSH causes an egg to mature; oestrogen rebuilds the lining. DAY 14: LH surges and triggers ovulation. DAYS 15-28: progesterone maintains the thickened lining, ready for a fertilised egg to implant.
A worked question: rising and falling together
A graph shows oestrogen rising through days 5 to 13, then LH spiking sharply around day 14. Why does the LH spike come just after the oestrogen peak? Rising oestrogen is what TRIGGERS the LH surge — the oestrogen peak signals the egg is ready, and that surge is what causes ovulation shortly afterwards. Reading the causal order off the graph, not just naming what each line does, is what a full-mark answer does.
Hormonal contraception works by disrupting the cycle
The contraceptive pill contains oestrogen and/or progesterone, taken to keep hormone levels artificially high and constant. This prevents FSH from being released, so no egg matures — without a maturing egg, the LH surge and ovulation never happen. Other hormonal methods (injection, implant, patch) use the same principle over different timescales.
Non-hormonal methods work by other means
A condom or diaphragm is a BARRIER method, physically stopping sperm reaching an egg. An intrauterine device (IUD) prevents implantation, and some also release hormones. Sterilisation surgically prevents eggs or sperm reaching each other permanently. None of these change the hormone cycle itself — they interrupt fertilisation or implantation by other means.
Comparing methods properly
A comparison question wants more than "the pill is hormonal and a condom is not". Hormonal methods are highly effective when used correctly but require remembering to take or replace them and can have side effects. Barrier methods are less consistently effective but have fewer hormonal side effects and, uniquely among these, a condom also reduces the spread of sexually transmitted infections — a point exam answers often miss. This lesson covers the biology the GCSE specification requires; families and schools differ on how and when the wider subject is discussed, and any personal question belongs with a trusted adult, not this page.