Dienogest (Natazia) is a hybrid progestogen that combines properties of both the 19-nortestosterone derivatives and the progesterone derivatives. It is indicated for use by women to prevent pregnancy and for the treatment of heavy menstrual bleeding in women without organic pathology. Dienogest is also approved in Europe, Australia, Malaysia, Singapore and Japan for the treatment of endometriosis. It is lowers the risk of becoming pregnant primarily by suppressing ovulation. Other possible mechanisms may include cervical mucus changes that inhibit sperm penetration and endometrial changes that reduce the likelihood of implantation. Dienogest exhibits highly selective binding to the progesterone receptor. It has high progestational and significant antiandrogenic activity, but only moderate antigonadotrophic activity. The most common adverse reactions in clinical trials for Natazia are headache (including migraines), breast pain, menstrual disorders, nausea or vomiting, acne, mood changes and increased weight.