Oestrogen and progesterone in the control of the menstrual cycle

Several hormones are involved in the menstrual cycle of a woman:

  • follicle stimulating hormone (FSH) causes the maturation of an egg in the ovary
  • luteinising hormone (LH) stimulates the release of the egg
  • oestrogen is involved in repairing and thickening the uterus lining, progesterone maintains the uterine lining

The menstrual cycle last for approximately 28 days and graphs can be used to follow changes to the hormones during this process.

A diagram representing the menstrual cycle and hormone levels
Question

Describe the change in levels of the two hormones during the 28 days.

Days 1 to 12 - oestrogen gradually increases and peaks approximately on the 12th day. Progesterone, stays approximately at the same level and begins to increase slightly from around day 12.

Oestrogen drops during days 13 and 14, and progesterone continues to gradually increase until about day 21, when it slowly beings to decrease again. Oestrogen mirrors this shape and also has a second lower peak at about day 21.

Interaction of oestrogen, progesterone, FSH and LH in the control of the menstrual cycle - Higher

  • The pituitary gland produces FSH which causes the development of a follicle in the ovary.
  • As the egg develops inside the follicle, the follicle produces the hormone oestrogen.
  • The oestrogen causes growth and repair of the lining of the uterus wall. Oestrogen inhibits FSH.
  • When oestrogen rises to a high enough level it causes a surge in LH from the pituitary which causes ovulation where an egg is released from the follicle (Day 14 of the cycle).
  • The follicle becomes the corpus luteum and this produces oestrogen and progesterone which inhibit FSH and LH production by the pituitary. This is an example of negative feedback.
  • Progesterone maintains the uterus lining (the thickness of the uterus wall).
  • If the egg has not been fertilised, the corpus luteum dies and progesterone levels drop. This causes menstruation, where the uterus lining breaks down - this is known as having a period.
HormoneGlandRole
FSH (follicle stimulating hormone)Pituitary glandCauses an egg to mature in an ovary. Stimulates the ovaries to release oestrogen.
OestrogenOvariesStops FSH being produced (so that only one egg matures in a cycle). Repairs, thickens and maintains the uterus lining. Stimulates the pituitary gland to release LH.
LH (luteinising hormone)Pituitary glandTriggers ovulation (the release of a mature egg).
ProgesteroneOvariesMaintains the lining of the uterus during the latter part of the menstrual cycle and during pregnancy.

If a woman becomes pregnant, the placenta produces progesterone. This maintains the lining of the uterus during pregnancy and means that menstruation does not happen.