Oestrogen and progesterone in the control of the menstrual cycle

Graphs can be used to follow changes to the hormones during the process of the menstrual cycle.

Graph illustrating the hormone levels during the menstrual cycleThe menstrual cycle

The interaction of reproductive hormones in the menstrual cycle - Higher

The hormones involved in the menstrual cycle interact:

Before ovulation

  • FSH causes the ovaries to develop a follicle containing an egg, and to produce oestrogen.
  • When the level of oestrogen reaches a certain point, it inhibits the release of FSH. This ensures that only one egg develops in each cycle.
  • Oestrogen also stimulates the release of LH from the pituitary gland. LH stimulates an egg to be released from the follicle (ovulation).

After ovulation

  • Progesterone is secreted from the empty follicle. It inhibits the release of LH and FSH.
  • Oestrogen also inhibits the release of LH and FSH.
  • If a woman becomes pregnant progesterone will continue to be produced by the placenta, preventing the maturation of another follicle.
Question

Explain how the four hormones work together to prepare the body for acceptance of a fertilised egg. [6 marks]

In your exam do NOT answer in bullet points. The answer here is broken up into bullet points to show you how you can gain marks for each bit of information you include.

  • FSH stimulates an egg cell to mature in an ovary. FSH also stimulates the ovaries to release oestrogen.
  • Oestrogen causes the uterus wall to thicken, so that it will be able to accept the egg if it gets fertilised. The oestrogen also stops FSH being released by the pituitary gland and so only one egg will mature per menstrual cycle. If FSH falls, eventually oestrogen falls too.
  • At day 14 there is a peak of LH, caused by oestrogen, and so the egg is released from the ovary.
  • The empty follicle releases the hormone progesterone.
  • Progesterone maintains the uterus lining ready for the implantation of a fertilised egg.
  • Oestrogen and progesterone inhibit LH so only one egg is released per menstrual cycle.
  • If a fertilised egg is not received by the uterus lining, then the levels of progesterone fall, leading to menstruation.
  • Low levels of oestrogen and progesterone mean that FSH is not inhibited and so the cycle starts again.