Endometrial immune profile in postmenopausal women receiving Menopausal Hormone Therapy: the role of lymphocyte subpopulations in the development of abnormal uterine bleeding

Relevance. Investigation of the endometrial immune profile in postmenopausal women receiving menopausal hormone therapy (MHT) is essential for understanding the mechanisms of abnormal uterine bleeding (AUB) and improving treatment safety. While the role of NK cells and T lymphocytes in reproductive regulation has been studied, endometrial lymphocyte subpopulations during MHT remain insufficiently explored. Objective. To evaluate changes in lymphocyte subpopulations (CD3+, CD3+/CD16+/CD56+, CD3–/CD16+/CD56+) in the endometrium of postmenopausal women receiving MHT and their association with AUB development. Materials and Methods . A randomized controlled trial included 106 postmenopausal women divided into three groups: control (n=34), MHT without AUB (n=35), and MHT with AUB (n=37). Endometrial pipelle biopsy was performed before and after 6 months of therapy. Flow cytometry was used for immunophenotyping. Results. After 6 months of MHT, significant increases in CD3+ and CD3–/CD56+/CD16+ cells were observed compared to baseline. The most pronounced changes occurred in the AUB group. Intergroup differences were statistically significant for both absolute and relative lymphocyte counts. Conclusion. Altered endometrial immune homeostasis may contribute to AUB development during MHT. These findings emphasize the relevance of immune profiling for individualized therapeutic strategies.