Thickened endometrium is a routine finding that can be seen in an ultrasound examination of a woman. Proliferation of the endometrium can be induced either due to non-pathological causes (i.e. during menstrual cycle and pregnancy), to pathological causes (i.e. in endometrial hyperplasia, cancer, presence of a polyp, polycystic ovarian syndrome (PCOS) or to certain drugs (i.e. tamoxifen and HRT - hormone replacement therapy).