I went to that same clinic for about 4 years of my childhood as I was living in that area, but I don't really remember much and I think I was too young to really understand anyway.
I have slight tremors in my hands, they are more noticeable sometimes more than others, but most of the time pretty easy to control. I think they are related to poor diet control when I was a teenager. I also have an 80% hearing loss in my left ear and I think this was related to the diet as well. I got a bunch of tests done at Madison, but no one could really figure out what happened- they just called it tinnitus.
I am surprised that your sister developed tremors this soon! (assuming that she has PKU and has been on the diet)
I hope things go well with your sister and your thyroid problems.