Norgestrel hormone molecule. Molecular model of the hormone norgestrel (C21H28O2), used in contra- ceptive pills and hormone replacement therapy (HRT). Atoms are depicted as rods and are colour- coded: carbon (orange), oxygen (pink) and hydrogen (white). Norgestrel (or levonorgestrel) is a synthetic progestogen hormone. It is used alone in the progestogen-only contraceptive pill (minipill), which has fewer side effects than the combined pill (in which it may be combined with an oestradiol). It is also used in combination with oestrogen drugs as a treatment for the symptoms of the menopause. As such, it can help to prevent osteoporosis (brittle bones).