Levonorgestrel

Levonorgestrel is a synthetic progestin used in contraceptive pills, emergency contraception, and hormonal intrauterine devices. It primarily prevents pregnancy by suppressing ovulation or thickening cervical mucus, depending on the formulation.

Ovulation: Ovulation is the release of an egg from an ovary during the menstrual cycle. Oral levonorgestrel emergency contraception works chiefly by delaying or preventing ovulation.
Levonorgestrel emergency contraception: Levonorgestrel emergency contraception is an oral treatment taken after unprotected sex to reduce the chance of pregnancy. This use relies on a short, high-dose regimen, ideally taken as soon as possible.
Ulipristal acetate: Ulipristal acetate is a selective progesterone receptor modulator used as emergency contraception and for uterine fibroids. It is an oral emergency-contraception alternative that can delay ovulation later in the cycle.
Menstrual cycle: The menstrual cycle is the recurring sequence of hormonal and reproductive changes involving the ovaries and uterus. Levonorgestrel’s contraceptive effect depends partly on where a person is in this cycle.
Emergency contraception: Emergency contraception consists of methods used after sex to reduce the likelihood of pregnancy. Levonorgestrel is one widely used oral option within this broader set of methods.
Cervical mucus: Cervical mucus is fluid produced by glands in the cervix that changes in amount and consistency across the menstrual cycle. Levonorgestrel thickens cervical mucus, making sperm passage more difficult.
Levonorgestrel intrauterine system: A levonorgestrel intrauterine system is a T-shaped device that releases the hormone inside the uterus for contraception or treatment. This long-acting formulation delivers hormone locally over several years.
Copper intrauterine device: A copper intrauterine device is a nonhormonal contraceptive device that releases copper ions inside the uterus. It provides emergency and long-term contraception without using a progestin.
Hypothalamic–pituitary–ovarian axis: The hypothalamic–pituitary–ovarian axis is the hormonal signaling system that regulates ovarian function and reproductive cycles. Levonorgestrel can alter hormonal signals that govern follicular development and ovulation.
Contraceptive efficacy: Contraceptive efficacy is the degree to which a method prevents pregnancy under specified conditions of use. Effectiveness of oral levonorgestrel emergency contraception depends on prompt use and timing relative to ovulation.

Linked from 4 pages

Oral contraceptive pillRelated: It is a common progestogen in combined and progestogen-only pills.