Abstract
Oral progestins have been used for the treatment of endometriosis and endometriosis-associated complaints for more than 40 years. The mechanism of action on the menstrual cycle is well understood; however, the mechanism of action on endometriosis is still a matter of debate. The different progestins are able to stop proliferation in endometriotic implants and to induce regressive change to certain degrees; they are not able to heal endometriosis because endometriosis is a chronic and recurrent disease. For this reason, no medical treatment can heal endometriosis and repeat medication is necessary in the medical management of this disease. Progestins – especially non-androgenic progestins – are well tolerated and have only few side-effects; they can be used repeatedly or continuously over a long period of time.