Progesterone receptor ligands for the treatment of endometriosis

Estrogen dependence and progesterone resistance play a crucial role in the origin and development of endometriosis. Therefore, hormonal therapies are currently the most effective treatment. Progestins are considered the first-line approach, especially for a long-term management. Progestins are synthetic compounds that mimic the effects of progesterone by binding progesterone receptors. Continuous use of progestins leads to the suppression of ovarian steroidogenesis with anovulation and low serum levels of ovarian steroids, causing endometrial pseudodecidualization. Moreover, they act by interfering on several endometriosis pathogenetic pathways, decreasing inflammation, provoking apoptosis in endometriotic cells, stimulating atrophy or regression of endometrial lesions, inhibiting angiogenesis, and decreasing expression of metalloproteinases, thus diminishing the invasiveness of endometriotic implants. Progestins are effective for pain relief and improvement of the quality of life (QoL). The side effects are limited, and the compounds are available in different formulations and routes of administration and represent, in most cases, an inexpensive treatment option. Dienogest, Medroxyprogesterone acetate and Norethisterone acetate are the labeled progestins for endometriosis, but other progestins, such as Dyhidrogesterone, Levonorgestrel and Desogestrel, have been shown to be effective in the treatment of endometriosis-associated pain. The present review aims to describe the available and emerging evidences on progestins used for the treatment of endometriosis.