Thyroid hormone transport in the serum of patients with thyrotoxic Graves' disease before and after treatment

mone binding have been studied in sera obtained from patients with thyrotoxic Graves ' disease, be-fore and after treatment, and in sera from a group of carefully matched normal controls. Specimens from patients with thyrotoxicosis displayed a de-crease in the thyroxine (T4)-binding capacities of T4-binding globulin (TBG) and T4-binding pre-albumin (TBPA), an increase in serum protein-bound iodine (PBI), and an increase in both the proportion and absolute concentration of free T4. In addition, a smaller than normal proportion of 131I-labeled T, was associated with TBG during filter paper electrophoresis. After treatment of thyroxicosis, the only residual abnormality detected was a very slight persistent decrease in the T4-binding capacity of TBPA, which did not appear to influence the overall thyroid hormone-plasma protein interaction significantly, regardless of whether this was assessed under basal conditions or after enrichment of specimens with stable T,. It is concluded that the persistent abnormalities in the peripheral metabolism of T4, previously re-ported to occur in some patients with treated Graves ' disease, probably do not stem from resid-ual abnormalities in the transport of T4 in the plasma but must arise from abnormalities in T