Well as my mother, a much older woman than you and I (post menopausal) is currently undergoing a 6mo trial treatment for hormone therapy, there is a possibility that yes three year after (even after such a short time) your body is still undergoing repair just as pregnant women will when they stop nursing (hopefully by choice or age of the child being determinants) as it really does take a major toll on the body. I mean geeze, it may take two to start the process And the baby only grows in one of those places. And if you have ever over worked yourself by giving too much one way or another the body will make a way for it to heal... Yes to the busies of the world it may suck being sick, but how else were you gonna slow down?

Anyway, my personal theory behind the effectiveness of Mirena is based solely on why it is impossible to get pregnant WHILE pregnant. The cervix actually builds a mucus plug after Mirena is inserted the same way it would once a fertilized egg enters the uterus to produce the progesterone hormone (preg. hormone) telling the body it needs to produce more and take in more as it has a big job to do.

Thus the only way a pregnancy usually happens while Mirena is inserted is in the fallopian tubes (eptopic preg.)which IS life threatening.

So because the body is receiving a hormone signal from the uterus it will react the same as a real preg. and take just as much time for the body to repair and return all levels to their original state.

And by the way I appreciate your question as it has allowed me to answer my own.