Menstrual Cycle and Fertility

What is the menstrual cycle?

• Shedding of uterus lining

• Repair of uterus lining

• Release of an egg

• Maintenance of uterus lining

What are the stages of the menstrual cycle?

• Days 1-4: if fertilisation and implantation don’t occur the uterus lining sheds and the egg is expelled with it

• Days 4-14: uterus lining thickens and blood vessels grow in preparation for the implantation of an egg

• Day 14: egg released from the ovary towards the uterus via the fallopian tube

• Days 14-28: uterus lining maintained for implantation

What hormones control the menstrual cycle?

• FSH

• LH

• Progesterone

• Oestrogen

What is the role of oestrogen?

Produced in the ovaries and caused the uterus lining to regrow and thicken.

What is the role of progesterone?

Maintains the uterus lining and supports a pregnancy if the egg is fertilised.

What is the role of FSH?

• Produced by the pituitary gland

• Triggers the development of a follicle in the ovaries to release oestrogen

• Causes the maturation of an egg in an ovary

How does oestrogen interact with other hormones?

• Secreted as a result of FSH

• Stimulated secretion of LH from the pituitary gland

• Inhibits secretion of more FSH from the pituitary gland

Why does oestrogen inhibit FSH production?

Ensure only one egg is matured in each cycle.

What is the role of LH ?

• Secreted by pituitary gland

• Transported in the bloodstream to the ovaries

• Surge in LH triggers ovulation

• Stimulated follicle to develop into a corpus luteum

What is corpus luteum?

• Produced by the remains of the follicle of an ovary, after an egg has been released

• Releases progesterone

• Degenerates after a few days

How does progesterone interact with other hormones?

• Inhibits the release of FSH and LH by the pituitary in a negative feedback cycle

• If no implantation occurs, progesterone levels decrease and uterus lining sheds

• FSH increases and the cycle starts again

What happens to progesterone levels if fertilisation and implantation occur?

The placenta produces progesterone so levels remain high. This prevents further ovulation and maintains uterus lining.

What hormones cam be taken to prevent pregnancy?

• Progesterone pill

• Progesterone combined with oestrogen pill

How does progesterone prevent pregnancy?

• Thickens the mucus in the cervix so sperm can’t swim

• Thins uterus lining, reducing likelihood of egg implantation

• Prevents ovaries from releasing the egg

How does oestrogen prevent pregnancy?

At high doses, oestrogen inhibits FSH production, preventing ovulation.

How does an IUD work?

• Small, T-shaped contraceptive fitted into womb

• 2 types: copper and hormonal

• Hormonal released low levels of progesterone and lasts 3-8 years

How does a copper IUD work?

• Kills sperm in the uterus

• Stops any fertilised embryos from implanting in the uterus lining

What hormones are used to treat infertility?

FSH and LH are given as they stimulate egg production, maturation, and ovulation.

How does IVF work?

• The mother is given FSH and LH to stimulate maturation of several eggs

• Eggs collected and fertilised by the fathers sperm in a dish in the lab

• Fertilised eggs become embryos

• One or two embryos inserted into the uterus

What are the risks of IVF?

• Hormones can cause physical stress

• Emotional stress