Hormonal control of the menstrual cycle

From puberty, eggs begin to mature in the ovaries. During a typical menstrual cycle, one mature egg is released from an ovary. This release is called ovulation. A cycle is commonly around 28 days long, but its length varies.

Hormones acting on the ovaries

The pituitary gland releases two hormones that act on the ovaries. Follicle stimulating hormone (FSH) stimulates an egg to mature inside a structure called an ovarian follicle. Luteinising hormone (LH) stimulates ovulation, releasing the egg from the ovary.

Hormones and the uterus lining

The ovaries produce oestrogen, the main female reproductive hormone. Oestrogen promotes the build-up of the uterus lining. After ovulation, progesterone helps maintain this lining.

If pregnancy does not occur, oestrogen and progesterone levels fall. The uterus lining is then shed during menstruation.

Sex hormones and secondary sexual characteristics at puberty

During puberty, the body produces more sex hormones. These hormones stimulate the development of secondary sexual characteristics: physical features associated with sexual maturity that are not the reproductive organs themselves.

Testosterone and physical changes

Testosterone, produced mainly by the testes, promotes changes including a deeper voice, increased facial and body hair, and greater muscle development.

Oestrogen and physical changes

Oestrogen, produced mainly by the ovaries, promotes changes including breast development and a wider distribution of body fat around the hips.

Sex hormones also help maintain the secondary sexual characteristics that develop.