What causes thyroid symptoms: TSH or T3/T4

[rennie369]

I was diagnosed with Hashimoto's disease many years ago. More recently I have started developing symptoms that could be associated with a hyperactive thyroid: hair loss, trembling hands, insomnia, irritability, sensitive to heat etc. I got my regular thyroid labs and it came back with a TSH of .2, but my T3 and T4 were right in the middle of the normal range (I forget the exact numbers). My question is whether the TSH levels are responsible of thyroid symptoms or if the T3 and T4 levels cause the sympotoms? With my T3/T4 in the normal range I am thinking maybe it is something other than a thyroid problem.

[Mark Lupo, M.D.]

TSH is a little low - not a definite link with your symptoms and thyroid.  If your are on thyroid hormone, then a slight dose decrease and re-eval in 6 weeks would be reasonable.  If not then rechecking TSH in the future would help determine if you are developing hyperthyroidism.  

[Super_sally888]

TSH does not cause symptoms, it just reflects whether the TSH is too high or too low.  The fact that the TSH is very low means that the FT3/FT4 may be too high for you, even though they are apparently mid-range.

However, given your symptoms it would be reasonable to assume thyroid may be causing these.

Are you taking thyroid replacement hormone?  If so a slight reduction in dose may help, and if it helps your symptoms, you'll have your answer.