Conservative management of endometrial hyperplasia or carcinoma with the levonorgestrel intrauterine system may be less effective in morbidly obese patients.

•Endometrial hyperplasia/carcinoma regression rates with LNG-IUS were examined by BMI.•Morbidly obese patients with EH/EHA/EC are more likely to progress.•Despite addition of oral progesterone to LNG-IUS, morbid obesity increases the odds of progression.