Several hormones are involved in the menstrual cycle of a woman:
The menstrual cycle last for approximately 28 days and graphs can be used to follow changes to the hormones during this process.
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.
|FSH (follicle stimulating hormone)||Pituitary gland||Causes an egg to mature in an ovary. Stimulates the ovaries to release oestrogen.|
|Oestrogen||Ovaries||Stops 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 gland||Triggers ovulation (the release of a mature egg).|
|Progesterone||Ovaries||Maintains 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.