4.2 THE ROLE OF HORMONES IN THE MENSTRUAL CYCLE

Menstrual Cycle• Menstrual cycle refers

to the changes in the uterus wall of a women that take place every 28 days, beginning from puberty (11 years old) until menopause (45-50 years old).

• Is regulated by hormones.

Menstrual Cycle & Hormones

Hormones involved:• Follicle stimulating hormone (FSH)• Luteinising hormone (LH)• Oestrogen• Progesterone

• The menstrual cycle occurs every 28 days.• A girl starts to menstruate when she reaches puberty.

• Baby girls are born with their OVARIES packed with all the EGGS that they will ever produce.

• These are IMMATURE• And do not develop completely until

their TEENS• When their monthly MENSTRUAL

CYCLE starts• MENSTRUATION is the blood

discharged from the vagina when the uterine lining breaks down.

• Menstruation occur when there is no fertilisation, and it last from 3 to 5 days.

• During this period, FSH stimulates the development of the folicles and the production of oestrogen to repair the uterus lining

• From day 5 to 13, the FSH and oestrogen level continue to increase & a Graafian Follicle is formed,

• On day 13, the LH level increase rapidly causing ovulation to take place on day 14.

• From day 15 to 25, the corpus luteum formed secretes progesterone which stimulates the endometrium of the uterusto become ticker & filled with blood vessels.

• If the ovum is not fertilised, the uterus lining breaks down & the corpus luteum degenerates. This causes the progesterone level to drop even further, follow by more breakdown of the uterine lining, which is discharge as menstrual flow.

• If the ovum is fertilised, the zygote developes into an embryo, which implants itself into the endometrium of the uterus.

• The corpus luteum continues to secrete progesterone and oestrogen until the placenta is formed.

• Progesterone inhibits the production of FSH & LH causing the menstrual cycle to stop during pregnancy.

PMS• Some women suffer from

Pramenstrual syndrome (PMS) a few days before menstrualtion, due to imbalance in the oestrogen & progesterone level

• During this period, the are often depressed, irritable & tired.

• Some suffer from headaches & backaches while others gain weight easily.

Menopause• Occurs when the menstrual cycle stops.• It occurs usually when a women reaches 45 to 50 years of age.• During this time, very little FSH is produced, resulting in lower

levels of oestrogen.• The follicles & uterus walls do not develop;• There is no ovulation & menstrual cycle is disrupted.• The menstruation eventually stops.