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11.6 Hormones and the Menstrual Cycle

GCSE Biology · AQA · Chapter 11: Hormonal Coordination

A free GCSE Biology lesson for AQA (8461) from OBA School: fSH, LH, oestrogen and progesterone and how they control the monthly cycle. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

  • Describe the main stages of the menstrual cycle
  • Name the four hormones of the cycle, where each is made and what it does
  • Explain how FSH, LH, oestrogen and progesterone interact (Higher tier)
  • Extract and interpret data from graphs of hormone levels (Higher tier)

Key words

  • Menstrual cycle: The monthly cycle of changes in the ovaries and uterus, about 28 days long.
  • Menstruation: A period: the lining of the uterus breaks down and is lost through the vagina.
  • FSH: Follicle stimulating hormone (pituitary): causes an egg to mature in an ovary.
  • LH: Luteinising hormone (pituitary): stimulates the release of an egg (ovulation).
  • Oestrogen: Hormone from the ovaries: builds up the uterus lining.
  • Progesterone: Hormone from the ovaries: maintains the uterus lining.

The stages of the cycle

  • Days 1 to 4; What happens Menstruation (a period): the uterus lining breaks down and is lost.
  • Days 5 to 13; What happens An egg matures in an ovary. The uterus lining builds up again, becoming thick and full of blood vessels.
  • About day 14; What happens Ovulation: the mature egg is released from the ovary into the oviduct.
  • Days 15 to 28; What happens The lining is kept thick, ready for a fertilised egg (embryo) to implant. If no egg implants, the lining breaks down and the cycle starts again.

Key fact: Day 1 of the cycle is the first day of a period. Cycle lengths vary from person to person; 28 days is a typical value.

The four hormones

  • FSH; Made by Pituitary gland; Main effect Causes an egg to mature in an ovary; stimulates the ovaries to make oestrogen
  • LH; Made by Pituitary gland; Main effect Stimulates the release of the egg (ovulation)
  • Oestrogen; Made by Ovaries; Main effect Makes the uterus lining grow and thicken
  • Progesterone; Made by Ovaries (from the empty follicle after ovulation); Main effect Maintains the thick uterus lining

How the hormones interact (Higher tier)

The hormones control each other, so the cycle repeats in the right order.

  • FSH causes an egg to mature and stimulates the ovaries to make oestrogen.
  • Rising oestrogen builds the lining, inhibits FSH (so no more eggs mature) and stimulates LH release.
  • A surge of LH around day 14 causes ovulation.
  • After ovulation the ovary makes progesterone, which maintains the lining and inhibits FSH and LH.
  • If the egg is not fertilised, progesterone falls. The lining breaks down (a period), and FSH is no longer inhibited, so a new egg starts to mature.

Reading hormone graphs (Higher tier)

Worked example: using the graph

Use the graph to explain why ovulation happens on about day 14.
Oestrogen peaks just before day 14 (1). High oestrogen stimulates the pituitary to release LH, so LH rises sharply (surges) (1). The LH surge triggers the release of the egg (1).

Answer: oestrogen peak → LH surge → ovulation

Worked example: a rate of change

The uterus lining is 2 mm thick on day 5 and 11 mm thick on day 14. Calculate the mean rate of growth.
Increase = 11 − 2 = 9 mm in 14 − 5 = 9 days. Rate = 9 ÷ 9

Answer: 1 mm per day

Exam tip: When asked about a graph, quote day numbers and say which hormone is rising, falling or at a peak.

Common mistakes

  • Saying LH “makes the egg mature”. FSH matures the egg; LH triggers its release.
  • Saying the pituitary makes oestrogen or progesterone. These are made by the ovaries.
  • Saying progesterone builds the lining. Oestrogen builds it; progesterone maintains it.
  • Thinking day 1 is ovulation. Day 1 is the first day of menstruation.

Revision questions

Try these, then check your answers below each one.

Question 1. Which gland makes FSH and LH? (Choose from: Ovaries, Pituitary gland, Thyroid gland, Uterus.)

Answer: Pituitary gland

Working: FSH and LH are made by the pituitary gland.

Question 2. In a typical 28-day cycle, when does ovulation usually happen? (Choose from: Day 1, About day 5, About day 14, Day 28.)

Answer: About day 14

Working: Ovulation usually happens around day 14 of a 28-day cycle.

Question 3. (Higher tier) True or false? Progesterone inhibits the release of both FSH and LH.

Answer: True

Working: True. Progesterone inhibits FSH and LH.

Related lessons

Continue in the full course

This lesson is section 11.6 (AGCBH1106) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.

 

 

 

 

 

 

 

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