Hormone Therapy Effects on the Uterus

The uterus and especially the endometrium are sensitive targets for steroid sex hormones, capable to modify structure and function with promptitude and versatility in order to secure reproductive functions. Hormone therapy is used to counteract deprivation, abnormal, and deleterious functions of "natural" hormones. It is widely prescribed, being used by millions of women all over the world. It seems that most women would use at least some hormone therapy at some point of their life, as contraceptives, ovarian stimulation, replacement therapy, or hormone antitumoral therapy. The diagnosis of uterine tissue, mostly of the frequently performed endometrial biopsies taken from women undergoing hormone therapy, is often confusing and difficult to interpret due to the complexity of histologic changes. Permanently changing hormonal pharmaceutical products, regimens, dosages, as well as new concepts of therapy are challenges for both users and medical prescribers. This chapter addresses the most commonly issues arising from the gynecological pathology interpretation of hormonal therapy effects on the uterus.