Sex Hormones and Oral Contraceptives

Key points

• • Oestrogen and progesterone are the main female sex hormones, controlling the menstrual cycle and preparing the body for pregnancy.
• • The combined oral contraceptive pill contains an oestrogen and a progestogen, and it mainly works by stopping the release of an egg (ovulation).
• • It also thickens the cervical mucus to block sperm and thins the lining of the womb, adding to its effect.
• • The progestogen-only pill is useful when oestrogen must be avoided, and it acts chiefly on the mucus and the lining of the womb.
• • A serious but uncommon harm of oestrogen-containing pills is an increased risk of blood clots (venous thrombosis), which is higher in smokers.