Hormonal Control of Menstruation (Female Fertility)

• Menstrual Cycle

  • Takes on average 28 days

  • Menstruation is day 1 to 5 of the cycle

  • Endometrium starts to repair

  • Ovulation day 14

  • Endometrium thick and spongy

  • Menstruation in absence of fertilised egg

  • Consists of 2 phases - Follicular phase & Luteal phase
• 1.. Follicular phase

  FSH

  • Causes development and maturation of follicles in ovary

  • Stimulates secretion of oestrogen by the follicle

  • Oestrogen stimulates the repair and proliferation of the endometrium.

  • Oestrogen affects the consistency of cervical mucus making it more easily penetrated by sperm

  • Eventually the high concentration of oestrogen triggers a surge of LH by the pituitary at around day 14.

  • The LH surge is the direct cause of ovulation.
• 2. Luteal Phase

  LH

  • After ovulation LH causes the follicle to develop into the corpus

  luteum. This gland-like structure secretes progesterone and

  oestrogen.

  • Progesterone promotes further development and vascularisation of

  the endometrium preparing it to receive a blastocyst if fertilisation

  occurs.
• Negative Feedback Effect of Ovarian Hormones on the Pituitary

  • High levels of oestrogen and progesterone have an inhibitory effect on the pituitary gland.

  • Decrease the levels of FSH and LH which prevents further follicles from

  developing.

  • The lack of LH leads to degeneration of the corpus luteum.

  • A drop in progesterone leads to menstruation.