My father is 91 years of age and his blood tests indicate low thyroxine levels however instead of making him feel better as others who have taken the medication testify to, he slows down and becomes garbled. I don t know if this can be attributed to senility or not but I know that if he needs to be more with it I take him off the thyroxine for a while. I have time and time again indicated this to doctors but they pay little attention because of course thyroxine is a natural substance that the body produces. What gives? YYYY@YYYY