Menopausal hormone use after hysterectomy in endometriosis: a Finnish register-based study

This study aimed to examine the frequency and type of menopausal hormone therapy (MHT) use after hysterectomy among women with surgically diagnosed endometriosis.
A retrospective register-based cohort study identified women with a first surgical diagnosis of endometriosis and a reference cohort using Finnish national registries. This study included women aged ≤45 years with hysterectomy and bilateral oophorectomy, and women >45 years with hysterectomy performed between 1996 and 2018. Women with a history of thrombosis, breast cancer or gynecological cancer were excluded. MHT use was identified from national reimbursement registry until the end of 2019.
Altogether 11,365 women were included: 1748 women aged ≤45 years and 9617 aged >45 years. Among women with endometriosis, 94.3% (aged ≤45 years) and 73.1% (aged >45 years) used MHT postoperatively, compared with 81.8% and 51.5% in the reference cohort (p < 0.001). Estrogen-only therapy was the most commonly used MHT, but the use of combined estrogen–progestin therapy increased significantly (p < 0.001).
MHT use was very common in women with endometriosis. The shift toward combined therapy reflects evolving international guidance. The high rate of MHT use underscores the need for studies assessing its long-term outcomes in women with endometriosis.
Endometriosis is a chronic, estrogen-dependent inflammatory disease affecting up to 10% of women of reproductive age. Although symptoms typically resolve after menopause, menopausal hormone therapy (MHT) has been suggested to potentially reactivate the disease. Progestin is recommended alongside estrogen therapy in women with a uterus to prevent endometrial hyperplasia, and in all patients with endometriosis to reduce the risk of recurrence.
Our objective was to determine the frequency and types of MHT used by women with endometriosis and hysterectomy between 1996 and 2019, utilizing Finnish national registry data. From a nationwide cohort of women with a first surgical diagnosis of endometriosis and their age-matched reference women, we selected two groups of women: women aged ≤45 years who had undergone hysterectomy with bilateral oophorectomy, resulting in surgical menopause; and women >45 years of age who had undergone hysterectomy. For comparison, we identified a non-matched reference group of women with hysterectomy.
We found that women with endometriosis were more likely to use MHT compared to the reference groups. Among women with endometriosis aged ≤45 years, 9 out of 10 used MHT after hysterectomy, compared to 7 out of 10 among those aged >45 years. The most used type of MHT was estrogen-only therapy. However, the use of combined estrogen–progestin therapy increased over time in line with international recommendations. There remains a lack of specific scientific knowledge on the benefits and risks of MHT in women with endometriosis, which may be limiting advances in clinical treatment.