Using progestins in clinical practice

Progestational agents have many important functions, including regulation o f the menstrual cycle, treatment of dysfunctional uterine bleeding, prevent ion of endometrial cancer and hyperplastic precursor lesions, and contracep tion. Because of the reported side effects of synthetic analogs called "pro gestins," there has been interest in replicating the natural hormone for cl inical use. Natural progesterone is obtained primarily from plant sources a nd 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. Adolesc ents and perimenopausal women may require progestational agents for the tre atment 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 contrace ptives can be used in women with contraindications to estrogen; however, ef ficacy requires rigorous compliance. New progestins for use in combination oral contraceptive pills were specifically developed to reduce androgenic s ymptoms. It is unclear whether these progestins increase the risk of venous thromboembolic disease. Progestin-only emergency contraception offers a re gimen that is more effective than combination oral contraceptive pills, wit h fewer reported side effects.