Initially, I recall overt hyper symptoms like increased energy, warmth, etc. I don't have clinical data to backup the symtoms though.
However, it is often a temporary effect until the body is used to the new higher nutrition status in Io-dine. If there is a problem getting used to the higher dose of I, then I assume that some people cannot tolerate various dosages for long depending on physiological status. Everyone's different is all I'm saying.