Hormones play an important role in human reproductive processes, including the menstrual cycle and puberty. During puberty, the body releases hormones that lead to the development of secondary sex characteristics. For example, the formation of facial hair in boys and the development of breasts in girls.
The menstrual cycle involves the monthly release of an egg from a woman’s ovaries.
There are four stages in the menstrual cycle.
Stage 1: On day 1 menstruation begins if there is no fertilised egg. This is where the uterus lining breaks down for 5 days.
Stage 2: From around day 5 to day 14, the uterus lining builds back up, ready to receive the egg.
Stage 3: Around day 14, the egg develops and is released from the ovary. This stage is called ovulation.
Stage 4: The uterus lining is maintained until day 28. If no egg is fertilised, the uterus lining breaks down, leading to menstruation. After this, the cycle restarts.
There are many hormones that regulate the menstrual cycle.
Follicle-Stimulating Hormone (FSH) is produced in the pituitary gland and it causes egg maturation in the ovaries. It then stimulates the ovaries to start releasing oestrogen.
Oestrogen is produced in the ovaries and promotes the thickening of the uterus lining. Also, oestrogen triggers the pituitary gland to release Luteinising Hormone (LH) and inhibits the release of FSH, ensuring only one egg matures per cycle.
Luteinising Hormone (LH) is produced by the pituitary gland and it triggers the release of the egg at day 14. This is known as ovulation.
Progesterone is produced by the ovaries and it helps to maintain the uterus lining.