Hormones are chemicals in the body that determine when and how the body grows

Hormones regulating the female reproductive system

Gonadotropin-releasing hormone (GNRH): produced by a part of the brain called hypothalamus.

Follicle-stimulating hormone (FSH): produced by the pituitary gland in the brain during the first half of the menstrual cycle. It stimulates the development of the maturing ovarian follicle and controls ovum production.

Leutenizing hormone (LH): produced by the pituitary gland. It stimulates the ovaries to produce oestrogen and progesterone. It triggers ovulation, and promotes the development of the corpus luteum ('yellow body' that develops from the ovary after ovulation)

Oestrogen: During the first half of the cycle, the ovaries make mostly oestrogen, which causes a thick lining of blood and tissue to grow in the womb. The body makes the lining so a baby would have a soft nest to grow in if the woman became pregnant.

Progesterone: During the last 14 days of the cycle, a woman also produces progesterone. Progesterone causes the lining of the womb to prepare for pregnancy.

The monthly cycle is different for each woman. It begins on the first day of a woman’s monthly bleeding. Most women bleed every 28 days. But some bleed as often as every 20 days or as little as every 45 days