The menstrual cycle in women is a recurring process in which the lining of the uterus (womb) is prepared for pregnancy, and if pregnancy does not happen, the lining is shed at menstruation.
Several hormones control this cycle, which includes controlling the release of an egg each month from an ovary, and changing the thickness of the uterus lining. These hormones are secreted by the ovaries and pituitary gland.
FSH
The hormone FSH is secreted by the pituitary gland. FSH makes two things happen:
- It causes an egg to mature in an ovary.
- It stimulates the ovaries to release the hormone oestrogen.
Oestrogen
The hormone oestrogen is secreted by the ovaries. Oestrogen makes two things happen:
- It stops FSH being produced (so that only one egg matures in a cycle)
- It stimulates the pituitary gland to release the hormone LH.
LH
The hormone LH causes the mature egg to be released from the ovary.
The top chart below shows how the level of oestrogen changes during the menstrual cycle. Progesterone is another hormone secreted by ovaries: it maintains the lining of the uterus and stays high during pregnancy.
The underneath chart how the levels of FSH and LH change during the menstrual cycle.
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[ This page has been adapted from www.bbc.co.uk/schools/gcsebitesize/science ]