How do oestrogen and progesterone regulate the menstrual cycle?

Oestrogen and progesterone regulate the menstrual cycle by controlling the growth and shedding of the uterine lining.

Oestrogen and progesterone are two key hormones that play a crucial role in the menstrual cycle. The menstrual cycle is a monthly process that prepares the female body for potential pregnancy. It involves several stages, each controlled by different hormones, including oestrogen and progesterone.

The menstrual cycle begins with the follicular phase, during which the pituitary gland releases follicle-stimulating hormone (FSH). This hormone stimulates the growth of several follicles in the ovaries, each containing an egg. As the follicles grow, they start to produce oestrogen. This hormone causes the lining of the uterus, or endometrium, to thicken in preparation for a potential pregnancy.

Around the middle of the cycle, a surge in oestrogen triggers the release of luteinising hormone (LH) from the pituitary gland. This causes the most mature follicle to burst and release its egg in a process known as ovulation. The ruptured follicle then transforms into a structure called the corpus luteum, which produces progesterone.

Progesterone prepares the endometrium for the implantation of a fertilised egg. It makes the lining of the uterus spongy and full of nutrients, ready to receive and nourish an embryo. If fertilisation does not occur, the corpus luteum breaks down, causing a drop in progesterone levels. This drop triggers the shedding of the uterine lining, or menstruation, marking the start of a new cycle.

In summary, oestrogen and progesterone work together to regulate the menstrual cycle. Oestrogen controls the growth of the uterine lining during the first half of the cycle, while progesterone prepares it for potential pregnancy during the second half. If no pregnancy occurs, a drop in progesterone levels leads to menstruation and the start of a new cycle.