What can cause low tsh of its not a thyroid or pituitary problem? 0.01 tsh t3 (liothyronine) and t4 free normal, graves and hasmitos negative

2 possibilities: Hi. First of all, Hashimoto's doesn't cause a suppressed TSH, and YES, your TSH is SUPPRESSED, not "low", because your free T4 and total T3 (liothyronine) are "normal". A low TSH (pituitary defect) would cause low free T4 and possibly/probably low T3 (liothyronine). The most likely is a "hot" thyroid nodule (autonomously hyper-functioning); second most likely would be a phase of subacute thyroiditis. Follow over time to tell.