2 yr old female toddler w/ enlarged ovaries/uterus and advanced bone age

My 2 year old daughter has enlarged ovaries, one larger then the other, stimulated uterus, breast tissue and a bone age of 3 1/2.  She has  had an MRI, blood work, Lupron Stimulation Test...all have come back clean.  The Dr. is somewhat confused as her Hormone levels are normal however her ultra sound is showing something totally different.  He had us go back for anohter ultra sound to see if it has progressed or if maybe it was a one time freak thing...it has progressed.  He has us going in for another Lupron Stimulation test this week...if this 2nd test comes back normal, what's next?  What could be causing all of this?  She doesn't have a tumor on her brain...her Hormone levels are normal.....Any help would be greatly appreciated.