Endometrial thickening, an ultrasonographic diagnosis, is a preliminary screening and diagnosis of what exactly is causing the thickening of the uterine lining. Oral progestin-based medications can be taken to produce a medicated curettage. If the endometrium is a simple proliferative type of endometrial tissue, medicated curettage can be performed by taking oral progesterone-based medications. In this way menstruation can show an abnormal increase after taking the medication, and a repeat ultrasound after menstruation may suggest that the endometrium is not as thick. If the ultrasound is repeated and the lining of the uterus is still thick, a hysteroscopy is necessary to clarify the possibility of polyps growing in the lining of the uterus.