Elevated serum concentrations of thyroxine-binding globulin and caeruloplasmin in methadone-maintained patients.

Patients on a methadone-maintenance program had high serum concentrations of thyroxine-binding globulin. This resulted in elevated serum thyroxine and triiodothyronine levels and low triiodothyronine uptake values. Their free thyroxine index was normal, as was serum thyroxine and triiodothyronine when related to thyroxine-binding globulin concentration. Serum caeruloplasmin concentration was also increased in methadone-treated patients.