Norethisterone (or norethindrone) is a molecule used in hormonal contraceptives. Norethisterone is a synthetic form, and therefore agonist, of the naturally occurring female sex hormone, progesterone. It is a member of the progestagen family and can be used to treat premenstrual syndrome, painful periods, abnormal heavy bleeding, irregular periods, menopausal syndrome (in combination with oestrogen), or to postpone a period.