My son was first diagnosed at age 5.  His bone age at that time was 10.5 .   Over that past 5 years his growth has been very slow...sometimes 1 cm in a year.  Our endo believed it was "catch down" time because he grew so rapidly prior to his diagnosis.  Now at age 10 his bones are the age of an 11 year old.  Primarily, he suggested the Lupron shot to maximize his growth...he is 4’9" now.  When my son showed reluctance to the shot we inquired about other options.  That was when he discussed letrozole.  We haven’t made any decisions yet, we just discovered this yesterday,  but feel that for our son letrozole would be best.  He wants to grow like his classmates rather than wait two years while taking Lupon.  Overall, our endo feels that because both my husband and I are tall, he has genetics on his side and will grow to approximately 5’9" with whatever treatment we choose.  It is comforting to hear that your son is doing well.  How old is he now?  What criteria does your son’s doctor use to determine when he will stop taking letrozole and allow the estrogen to fuse his growth plates?  Thank you for your reply.