Researchers are looking for a better way to treat women with nonatypical endometrial hyperplasia (NAEH). Endometrial hyperplasia is a condition where the lining of the uterus (called the endometrium) becomes too thick. Nonatypical means that the condition is not cancerous. It is often caused by hormone imbalances in women. Symptoms can include abnormal vaginal bleeding or irregular periods. If this condition is not treated, then it may lead to cancer. Currently, there are no approved treatments for NAEH and that is why there is still an unmet medical need. The study treatment, Mirena (also known as BAY 865028), is already available as a type of birth control device. It is inserted into the uterus where it gradually releases progesterone. In this study, researchers want to find out if Mirena works for women with NAEH. They believe it can help by keeping hormone levels balanced in the body. The main purpose of this study is to show that uterine lining goes back to completely normal lining after treatment with Mirena and that its use is safe in this population. For this, the researchers will compare the number of participants with benign endometrium after 6 months of treatment with Mirena or oral MPA. The study participants will be randomly assigned into one of two treatment groups. The randomization will be done 2:1 ratio, meaning that for every two participants assigned to Mirena, one will be assigned to oral medroxyprogesterone acetate (MPA). Based on their group, participants will receive Mirena, which is inserted into the uterus at the start of the study, or they will take progestins once daily by mouth for 6 months. Each participant will be in the study for around 10 months with up to 5 visits to the study clinic/site. Participants will visit the study clinic: * once before the treatment starts * 3 times with a gap of 3 months between the visits during the treatment * then 1 more time after the treatment ends During the study, the doctors and their study team will: * check participant's health by performing tests such as blood and urine tests * perform vaginal ultrasound and hysteroscopy. Hysteroscopy is a minor surgical procedure where a thin camera will be inserted into the womb to check for any abnormality. Sampling of the endometrial lining (cells in the womb) will be done with a thin tube at the same time. * take samples of womb (endometrial) lining * ask the participants questions about how they are feeling and what adverse events they are having An adverse event is any medical problem that a participant has during a study. Doctors keep track of all adverse events, irrespective if they think it is related or not to the study treatment.