SB7d-Hormones and the menstrual cycle

• What four hormones control the menstrual cycle?

  Oestrogen, progesterone, FSH and LH
• Oestrogen

  • Produced in the ovaries
  • Role= Causing the uterus lining to develop
  • Can also stimulate LH release
• Progesterone

  • Produced in the ovaries
  • Role= Thickening and maintaining of the uterus
• Luteinising Hormone (LH)

  • Produced in the Pituitary gland
  • Role= Triggers ovulation
• Follicle stimulating hormone (FSH)

  • Produced in the Pituitary gland
  • Role= Stimulates egg to mature in the ovaries
• Explain how FSH, LH, Oestrogen and Progesterone interact to control the menstrual cycle

  1. Low levels of progesterone allows FSH to be secreted from the pituitary gland, causing a follicle in the ovary to mature
  2. As it matures, it secretes oestrogen which inhibits FSH, and starts to thicken the lining of the uterus
  3. A high concentration of oestrogen causes a surge in LH from the pituitary gland
  4. This causes ovulation when the egg is released from the follicle
  5. The ruptured follicle becomes a corpus luteum which secretes progesterone and some oestrogen
• Explain how FSH, LH Oestrogen and Progesterone interact to control the menstrual cycle P2

  6. This causes the uterus lining to thicken even more

  7. Progesterone inhibits FSH and LH

  8. If the egg is not fertilised, the corpus luteum breaks down, and the progesterone concentration falls

  9. This triggers menstruation

  10. FSH is no longer inhibited so it can be secreted again
• Assistive Reproductive Therapy (ART)

  Women who are naturally infertile but want a baby can increase fertility by using hormones. This can be done through IVF and clomiphene treatment.
• Fertility drugs

  Women who have low levels of FSH can be given fertility drugs like clomifene to increase levels of FSH and LH, in order to mature eggs and stimulate ovulation. This also blocks actions of negative feedback of LH by oestrogen.
• What does IVF stand for?

  In vitro fertilisation
• What is IVF?


  Fertilisation outside a womans body.
• What are the steps of IVF?

  1. Fertility drugs are given (FSH and LH) to the woman to stimulate eggs to mature
  2. Eggs are taken from the ovaries
  3. The eggs are mixed with sperm in a dish for fertilisation
  4. If successful, the fertilised eggs develop into embryos in an incubator as it has the optimum temperature for enzymes
  5. When the embryos are tiny balls of cells, one or two of them are placed into the mothers womb to develop
• What is done if the man has a low sperm count?

  A procedure will be done called ICSI, which stands for Intra cytoplasmic sperm injection.

  
  

  This is when sperm taken from the man and is injected into the egg cell with a tiny needle
• Why is FSH still used in fertility drugs even if the woman ovulates naturally?

  This is to stimulate the maturation of many eggs, increasing the success rate. In a normal cycle, only one egg would mature.
• What are the pros of IVF?

  Pros-

  • Allows infertile couples to have babies
  • Developments in microscopy allows to remove single cells from embryo to test for disease. This can also allow the couple to choose characteristics for their baby, but it is illegal. (Designer babies)
• What are the cons of IVF?

  Cons-

  • Doesn't always work, in the UK it is a 1 in 4 chance of success
  • It is emotionally upsetting
  • It is physically unpleasant as it can cause abdominal pain and vomiting
  • IVF can lead to multiple births, increasing the risk of complications
  • IVF can be seen as unethical as unused embryos are destroyed