So confused why prescribed prometrium (micronized progesterone) for just thick uterine lining if its used to thicken lining?

Let me help. Prometrium (micronized progesterone) is a type of progesterone. Progesterone stabilizes the lining of the uterus and tells it not to get any thicker. When you stop taking the progesterone, a few days later the lining will come out like a period. It's actually the estrogen that makes the lining grow thicker and the Progesterone that stabilizes the lining.