QuestionLast year during a routine blood workup it showed my TSH is below normal range, but both T3 and T4 were within normal, the doctor mentioned this but did not seem to be concerned. Recently I has had vision problems in one eye, at first double vision, then within a week it just became blurred, and knowing hyperthyroidism can cause this I went to the doc and she did another blood test, same values. I went to the opthomologist and he found nothing wrong. He sent me to a neurologist and I was given a clean bill of health and referred me to a neuro opthomologist, who ran his tests and did not find anything wrong. Can subclinical hyperthyroidism cause vision problems even if T3 and T4 are both within normal parameters? I cannot seem to get answers from any of my doctors. Any guidance would be very much appreciated, thank you.
AnswerThis is a complicated subject that is full of personal bias. I will give you my read on it. (There are controversial medical books written on this subject)
If the thyroid is going to "go crazy" and become disconnected from the normal feedback regulation loop, it goes pretty crazy. It sounds like you are outside of the normal range. Now, the normal range means the range that 95% of normal people fall in to. The flipside of that means 5% of normal people are outside that range.
Only free T4 is active (the hormone that really affects the body) Most of it is bound by a protein (TBG) If your free T4 is relatively normal and your TSH is not "Undetectable" then there is nothing to be done except recheck in 6 months or a year unless the clinical situation changes.
Your eyesight problems as you describe have nothing to do with the thyroid. So you need to look elsewhere for the cause. But don't stay preoccupied with the thyroid stuff.... unless you have symptoms of hyperthyroidism, just recheck it routinely..... I hope this helps.
