Using progestins in clinical practice.

Progestational agents have many important functions, including regulation of the menstrual cycle, treatment of dysfunctional uterine bleeding, prevention of endometrial cancer and hyperplastic precursor lesions, and contraception. Because of the reported side effects of synthetic analogs called "progestins," there has been interest in replicating the natural hormone for clinical use. Natural progesterone is obtained primarily from plant sources and is currently available in injectable, intravaginal and oral formulations. An oral micronized progesterone preparation has improved bioavailability and fewer reported side effects compared with synthetic progestins. Adolescents and perimenopausal women may require progestational agents for the treatment of dysfunctional uterine bleeding resulting from anovulatory cycles. These agents may also be used in women at risk for endometrial hyperplasia because of chronic unopposed estrogen stimulation. Progestin-only contraceptives can be used in women with contraindications to estrogen; however, efficacy requires rigorous compliance. New progestins for use in combination oral contraceptive pills were specifically developed to reduce androgenic symptoms. It is unclear whether these progestins increase the risk of venous thromboembolic disease. Progestin-only emergency contraception offers a regimen that is more effective than combination oral contraceptive pills, with fewer reported side effects.