Hello all. I wanted to ask for interpretations of my recent thyroid lab results. With some context, the last 2 labs I had done, one in December and one just a few days ago in March, showed that I had very low TSH. I have Hashimoto's and this was very strange to me because it would indicate I am over medicating with levothyroxine, though I still have all the telltale signs of hypothyroidism - I'm always cold, fatigued, have dry skin, etc. My TSH in December was 0.109 uIU/mL (the range in 0.45-4.5), so I decreased my medication slightly to try to get the labs better but not feel too hypothyroid. After having been on the new dose for 2 months I got my tests done again and now my TSH is even lower! - 0.079, even though I hace worse hypothyroid symptoms than I had before the dose decrease.
My endocrinologist only tests TSH and Ft4, which is what I had done in December, so this time I went to my primary doctor to have a full thyroid panel done.
Most recent test results:
TSH: 0.079uIU/mL (0.45-4.5 reference)
T4: 10.3ug/dL (4.5-12 reference)
Free T4: 1.74ng/dL (0.82-1.77 reference)
T3: 99ng/dL (71-180 reference)
I do not know why she didn't test free T3 but I can't go back to get more tests done so this is what I have.
From what I have read, you want total T3 to be in the upper 30% of the reference range to be considered optimal and most people with Hashimoto's have symptoms if it is any lower than that. My total T3 is significantly lower than that; it is in the lower 30% of the reference range. But my FT4 and T4 are on the high end of their reference ranges.
So I'm wondering, could the reason I have hypothyroid symptoms be because my body is having trouble converting T4 to T3 even though my TSH is so low? And also, what does TSH react to - T4 levels or T3 levels? Is my TSH low because my pituitary is reacting to my high T4 and ignoring my lower T3 levels?