Hormones are a very important part of human reproduction such as in the menstrual cycle and puberty. During puberty, your body releases hormones which cause secondary sex characteristics to develop. For example, the formation of facial hair in boys and the development of breasts in girls.
The menstrual cycle includes the monthly release of an egg from the ovaries in a woman.
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 there is no fertilised egg, then the uterus lining breaks down, resulting in menstruation. So the cycle starts again.
There are many hormones involved in the menstrual cycle.
Follicle-Stimulating Hormone (FSH) is produced in the pituitary gland and it causes an egg to mature in the ovaries. It then stimulates the ovaries to start releasing oestrogen.
Oestrogen is produced in the ovaries and causes the growth (thickening) of the uterus lining. Oestrogen also stimulates the pituitary gland to release luteinising hormone (LH) and it stops FSH from being released, so that only one egg matures per cycle.
Luteinising Hormone (LH) is produced by the pituitary gland and it stimulates the release of the egg at day 14 (ovulation).
Progesterone is produced by the ovaries and it helps to maintain the uterus lining.