Hormonal interaction in menstrual cycle

• The levels of the four hormones fluctuate throughout the cycle
• They also interact with each other to promote or inhibit the release of other hormones
• 1. FSH

  • Produced in the pituitary gland
  • Causes an egg to mature in ovary
  • Stimulates ovaries to produce oestrogen
• 2. Oestrogen

  • Produced in ovaries
  • Causes lining of uterus to grow
  • Stimulates the release of LH and inhibits release of FSH
• 3. LH

  • Produced by pituitary gland
  • Stimulates release of an egg at day 14 (ovulation)
• 4. Progesterone

  • Produced in ovaries by the remains of the follicle after ovulation
  • Maintains lining of uterus during second half of cycle
  • When level of progesterone falls, lining breaks down
  • Also inhibits release of LH and FSH
• Change in the level of one hormone can be used to predict change in the level of another hormone:

  • FSH stimulates ovaries to produce oestrogen, so if FSH level rises oestrogen level would rise too
  • Increasing oestrogen level will then inhibit FSH release causing FSh to drop