Interpretation of laboratory tests of thyroid function in chronic active hepatitis.

Because the incidence of thyroid disorder is much greater than expected in chronic active hepatitis we have evaluated routine in vivo and in vitro tests of thyroid function in forty one clinically euthryoid patients with chronic active hepatitis and in five patients with chronic active hepatitis and concomitant or previous clinical thyroid disease. Serum thyroxine, thyroid hormone binding, triiodothyronine, thyrotrophin releasing hormone tests and thyroidal uptake of radio-iodine all gave misleading information in some clinically euthyroid patients with chronic active hepatitis. However, the free thyroxine index calculated from the serum thyroxine and thyroid hormone binding level gave results that accorded with the clinical impression in all but two of the euthyroid patients whose results were borderline and subsequently normal and in all but one of those with past or current thyroid disorder. This suggests that anomalies of protein binding accounted for abnormal results in thyroxine and thyroid hormone binding levels.