[Plasma levels of 3,3', 5'-T3 (reverse-T3) under various functional thyroid conditions].

Reverse T3 (r-T3) was measured in unextracted human plasma under different clinical conditions. The mean normal concentration was 0.20 ng/ml. In thyreotoxic patients r-T3 was elevated in the majority of the cases, however, it was normal in three cases of T3-toxicoses. Thyrectomized patients during different hormon substitution showed r-T3 levels corresponding to the T4 concentrations measured. Patients with severe chronic illnesses and low T3 showed normal to considerably elevated r-T3 levels. According to these results r-T3 is not of additional value in the diagnosis of thyroid disorders.