The causes of a thickened endometrial stripe include endometrial cancer and aging – menopausal women typically have thicker endometrial stripes than younger women, according to OncoLink. Medications such as tamoxifen may also cause thickened endometrial stripes, according to BreastCancer.org.
Although thickened endometrial stripes are normal in post menopausal women, if they are thicker than 4 mm and combined with post-menopausal bleeding, the American Congress of Obstetricians and Gynecologists identifies that as a cause for concern, according to OBG Management. However, a 2010 study from the Department of Obstetrics and Gynecology at the University of Virginia Health System suggests that doctors should be concerned at stripes thicker than 3 mm as type 2 endometrial cancer patients often exhibit stripes thinner than 4 mm.
The endometrium is the inner lining of a woman's uterus. Every month that a fertile woman is not pregnant, her endometrium thickens to create a place for an embryo to grow. If she is not pregnant, she sheds the extra endometrial lining and any unneeded blood as she menstruates. If the endometrium begins to develop out of control and invade other parts of the body, clumps of emdometrium form tumors, some of which are benign and some of which may be cancerous, explains OncoLink.