T3-resin test in familial dysalbuminemic hyperthroxinemia

The radiolabeled T3 (*T3) binds normally to available binding sites on TBG, but cannot bind to available sites on the abnormal albumin; as a result, the amount left over to bind to the resin is normal. The serum total T4 is high due to excess binding to the abnormal albumin, the T3-resin uptake and THBR are normal, and the serum free T4 index is high.