Oestrogen and progesterone in the control of the menstrual cycle
Several Chemical messenger produced in glands and carried by the blood to specific organs in the body. are involved in the menstrual cycle of a woman:
- follicle stimulating hormone (Follicle Stimulating Hormone. It stimulates oestrogen production and the growth of follicles (egg-sacs) in the ovary. It is secreted by the pituitary gland.) causes the maturation of an egg in the ovary
- luteinising hormone (Luteinising Hormone, secreted by the pituitary gland, which stimulates ovulation.) stimulates the release of the egg
- A female sex hormone produced in the ovaries, which is responsible for puberty in girls and the regulation of the menstrual cycle. is involved in repairing and thickening the uterus lining, Sex hormone produced by the ovaries and placenta. 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.
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 Fluid filled ball of cells found in the ovary containing an ovum (egg). 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 Also known as a womb. This is where the fertilised egg (ovum) develops. wall. Oestrogen inhibits FSH.
- When oestrogen rises to a high enough level it causes a surge in LH from the pituitary which causes The process of releasing an egg from an ovary. where an egg is released from the follicle (Day 14 of the cycle).
- The follicle becomes the The remains of the follicle in a mammalian ovary after it has released an ovum (egg) into the fallopian tube. The corpus lutuem secretes hormones involved in the menstrual cycle. and this produces oestrogen and progesterone which inhibit FSH and LH production by the pituitary. This is an example of Mechanism to lower raised levels of something, and to raise reduced levels of something..
- 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.
| Hormone | Gland | Role |
| 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. |
| Hormone | FSH (follicle stimulating hormone) |
|---|---|
| Gland | Pituitary gland |
| Role | Causes an egg to mature in an ovary. Stimulates the ovaries to release oestrogen. |
| Hormone | Oestrogen |
|---|---|
| Gland | Ovaries |
| Role | 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. |
| Hormone | LH (luteinising hormone) |
|---|---|
| Gland | Pituitary gland |
| Role | Triggers ovulation (the release of a mature egg). |
| Hormone | Progesterone |
|---|---|
| Gland | Ovaries |
| Role | Maintains the lining of the uterus during the latter part of the menstrual cycle and during pregnancy. |
If a woman becomes pregnant, the The organ in the uterus of pregnant mammals that allows the transfer of nutrients and waste products between the mother and the fetus through the umbilical cord. produces progesterone. This maintains the lining of the uterus during pregnancy and means that menstruation does not happen.