Levonorgestrel

**Semantic type:** Pharmacologic Substance

**Definition:** The levorotatory form of norgestrel and synthetic progestogen with progestational and androgenic activity. Levonorgestrel binds to the progesterone receptor in the nucleus of target cells, thereby stimulating the resulting hormone-receptor complex, initiating transcription, and increasing the synthesis of certain proteins. This results in a suppression of luteinizing hormone (LH) activity and an inhibition of ovulation, as well as an alteration in the cervical mucus and endometrium.

**Synonyms:** - (17Alpha)-13-ethyl-17-hydroxy-18,19-dinorpregn-4-en-20-yn-3-one - 13-Ethyl-17-hydroxy-18,19-dinor-17alpha-pregn-4-en-20-yn-3-one - 18-Methylnorethisterone - D-(-)-Norgestrel - L-norgestrel - LEVONORGESTREL - Mirena - Norplant - Plan B - Plan B - levonorgestrel