Endometriosis is a chronic, estrogen-dependent disease affecting women of reproductive age, associated with pelvic pain, infertility, and reduced quality of life. Progestins are the standard first-line therapy, but long-term treatment requires well-tolerated regimens that balance efficacy with patient satisfaction.

This study will compare two combinations of progestins with natural transdermal estradiol-dienogest versus drospirenone-to evaluate which regimen provides greater patient satisfaction after 6 months of therapy.

Endometriosis is a chronic, estrogen-dependent disorder characterized by the presence of endometrial tissue outside the uterine cavity. This ectopic tissue induces chronic inflammation, fibrosis, and adhesions, often resulting in pelvic pain, dysmenorrhea, dyspareunia, infertility, and impaired quality of life. The condition affects an estimated 6-10% of women of reproductive age, with peak prevalence between 25 and 35 years, making it one of the most common gynecological diseases with significant social and economic impact.

Available treatments for endometriosis are symptomatic rather than curative. Medical management is considered the cornerstone of therapy, especially in women who are not seeking immediate pregnancy. Current guidelines recommend progestins as first-line treatment due to their proven efficacy in suppressing endometriosis-associated pain and their favorable safety and tolerability profile. However, because therapy is usually long-term until menopause and continuous, optimal regimens must combine efficacy with good tolerability and sustained patient satisfaction.

Dienogest is an established fourth-generation progestin widely used in endometriosis management, with well-documented efficacy and safety. Drospirenone, another fourth-generation progestin, combines progestogenic, anti-androgenic, and anti-mineralocorticoid activities. Although marketed primarily as a contraceptive, drospirenone has shown promising results in controlling endometriosis symptoms and improving patient-reported outcomes.

Progestin-only regimens may lead to hypoestrogenic adverse effects, including vaginal dryness, mood disturbances, reduced libido, irregular bleeding, and bone loss. For this reason, the addition of natural estradiol is considered advantageous, as it may prevent atrophic changes, support bone metabolism, and improve overall quality of life. Transdermal estradiol, in particular, avoids hepatic first-pass metabolism, does not induce prothrombotic liver factors, and is associated with a lower risk of thromboembolic events compared with ethinyl estradiol.

This observational study is designed to directly compare two therapeutic strategies for women with endometriosis: Dienogest + transdermal estradiol or Drospirenone + transdermal estradiol.

The primary endpoint is patient satisfaction after 6 months of treatment, reflecting the central importance of patient-centered outcomes in a chronic disease that impacts multiple aspects of daily life. Secondary endpoints include sexual function, psychological well-being, and health-related quality of life, assessed with validated questionnaires.

By comparing two modern progestin-based regimens combined with natural estradiol, this study aims to generate evidence that will help clinicians tailor hormonal therapy to improve not only symptom control but also the long-term well-being and quality of life of women with endometriosis.

Inclusion Criteria:

• women who have been on combination therapy for at least 6 months with progestin and transdermal natural oestrogen (Dienogest + transdermal oestradiol or Drospirenone + transdermal oestradiol);
• women who have performed follow-up at least 6 months after the start of treatment and for whom data on the primary endpoint of the study (treatment satisfaction) are available.

Exclusion Criteria:

• absence of surgical diagnosis or imaging indicative of endometriosis or adenomyosis;
• women who have taken GnRH analogue therapy within 6 months prior to treatment with dienogest + transdermal oestradiol vs. drospirenone + transdermal oestradiol
• women who have taken only progestogen therapy without transdermal oestradiol or with contraindications to oestrogen use;
• women who received surgical indications during the treatment period, including obstructive uropathy or symptomatic bowel stricture; evidence of complex ovarian cysts or ovarian endometriomas with a diameter greater than 5 cm on transvaginal ultrasound.

Women with endometriosis referred to the endometriosis outpatient clinic of the Gynaecology SC of the Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico in Milan between October 2024 and September 2025 will be included in the study. The diagnosis of endometriosis is made on the basis of the combination of symptomatology + gynaecological examination, transvaginal/transrectal ultrasound or previous surgical visualisation of the disease.