I saw your questions about
your young son with UC. I'm sorry to hear that one so young is dealing with UC. Many hugs out to him and to you :)
I thought I'd try to answer at least one of your questions.
Hair loss due to imuran or other meds will usually decrease with time or with stopping the meds. I've lost hair because of prednisone and it's come back - a couple of times. Sometimes the hair loss is due to the fact that the body is fighting the fight and just doesn't have the resources to deal with hair.