A B S T R A C T Administration of phenobarbital to rats in a dosage schedule previously demonstrated to increase hepatocellular binding of thyroxine results in increased hormonal turnover, due both to increased deiodination and to fecal disposition of thyroxine iodine. The rate of biliary excretion of thyroxine iodine is roughly proportional to the hepatic content of exchangeable thyroxine. The...

We describe a reproducible radioimmunoassay, with use of Sephadex columns, for measuring normalized thyroxine. In comparison with a competitive protein-binding procedure, the present method is more specific because antibody rather than thyroxine-binding globulin is responsible for the competition between endogeneous and tracer thyroxine. In barbital buffer, various concentrations of thyroxine b...

Eight normal subjects were administered tracer amounts of a (14)C-labeled thyroxine, L-[tyrosyl-(14)C] T(4), by multiple injections. Then serial blood samples were collected for isolation of the thyroxine, triiodothyronine, and tetraiodothyroacetic acid fractions by a combination of column and paper chromatographies. The chromatographic artifacts were corrected by adding to the sera a purified ...

Thyroxine-induced epilepsy is a very rare condition occurring in epileptic patients. Here we report a boy with thyroxine-induced hypermotor seizure (HMS) following thyroxine administration for his central hypothyroidism secondary to surgery and cranial radiation for his brain tumor. After 3 years seizure-free period, he had repeated HMS, seven to eight attacks per day, after initiation L-thyrox...

Compartmental analysis of the peripheral distribution of labeled thyroxine was applied to various groups of subjects with thyrotoxicosis and hypothyroidism. It was observed that the hepatic incorporation of thyroxine was augmented in subjects with Graves' disease when compared to non-Graves' disease control groups at all levels of thyroid function. Decreased values of hepatic incorporation occu...

Thyroxine has been shown to accelerate the synthesis of carbamyl phosphate synthetase in the liver of Rana catesbeiana. Stimulation of carbamyl phosphate synthetase synthesis by thyroxine appears to be relatively specific because of the following observations: (1) succinoxidase activity decreased during the time that carbamyl phosphate synthetase increased; (2) liver catalase responded more slo...

BACKGROUND Patients with hypothyroidism are usually treated with thyroxine (levothyroxine) only, although both thyroxine and triiodothyronine are secreted by the normal thyroid gland. Whether thyroid secretion of triiodothyronine is physiologically important is unknown. METHODS We compared the effects of thyroxine alone with those of thyroxine plus triiodothyronine (liothyronine) in 33 patien...

In previous work the existence of free thyroxine in human serum was verified by dialysis through cellophane; the concentration of the unbound hormone in normal human serum was found to approximate one-thousandth of the total thyroxine (1). This direct measurement of free thyroxine was in reasonable agreement with the theoretical value computed from data on the per cent of total thyroxine bound ...