I have had primary hypothyroidism for the last 17 years. About a year and a half ago, my TSH went well below normal (approx. .015) and has stayed there, despite lowering my synthroid dose. Now my free T3 is also below normal and T4 is in the bottom half of normal. I am also starting to have symptoms I remember from being hypo: cold all the time, gaining weight, sluggish. My doctor wants to lower the synthroid dose even farther. I have two questions. One: should the synthroid dose be lowered again when T3 is already low and T4 is going down? Two: what could be causing the low TSH? I had an MRI and pituitary was normal.