During puberty, reproductive hormones cause the secondary sex characteristics to develop. Testosterone is the main male reproductive hormone. It is produced by the testes and stimulates sperm production. Oestrogen is the main female reproductive hormone and is produced in the ovary. At puberty eggs begin to mature, and one is released approximately every 28 days. This is called ovulation.
Several hormones control the menstrual cycle of a woman. Follicle stimulating hormone (FSH) causes maturation of an egg in the ovary. Luteinising hormone (LH) stimulates the release of the egg. Oestrogen and progesterone are involved in maintaining the lining of the uterus.
Higher tier only: the hormones interact. FSH is released by the pituitary gland and stimulates the ovary to produce oestrogen. Oestrogen causes the uterus lining to build up and, when it is high, stimulates the pituitary gland to release LH, which triggers ovulation. After ovulation the empty follicle makes progesterone, which keeps the lining thick. Progesterone and oestrogen inhibit FSH. On a graph of hormone levels, oestrogen peaks before LH, and progesterone peaks after ovulation. If no pregnancy occurs, progesterone falls and the lining breaks down.
