Levonorgestrel

Levonorgestrel is a synthetic progestin and a derivative of 19-nortestosterone. Levonorgestrel suppresses the hypothalamic-pituitary-gonadal axis through negative feedback, reducing the LH surge required for normal follicular rupture and thereby inhibiting or delaying ovulation. Levonorgestrel also thickens cervical mucus, which hinders sperm passage through the cervix into the uterine cavity and reduces the likelihood of fertilization. In addition, levonorgestrel maintains the endometrium in a thinner, non-proliferative state, making embryo implantation less favorable even if fertilization occurs.