A method for determining thyroxine-binding globulin (TBG) concentration as the total thyroxine-binding capacity, has been developed. Prior electrophoretic separation of the three serum thyroxine-binding proteins is not required. Serum samples are diluted with a barbital-salicylate buffer pH 8.6, which inhibits thyroxine-binding by prealbumin. After incubation with 100 g/10O ml thyroxine contain...

atrial fibrillation or osteoporosis and makes the illogical extrapolation that a patient given a dose of thyroxine that suppresses or brings the serum thyroxine concentration to higher than the reference range is receiving too much replacement. It is excusable for doctors to believe that if the serum thyroxine concentration is higher than the so-called normal range that the dose of thyroxine sh...

SYNOPSIS A trial was carried out on 134 patients of new kits (Ames Co) using columns of Sephadex G-25 for the determination of serum total thyroxine (Tetralute test) and for the indirect estimation of serum free thyroxine-binding globulin capacity (Trilute test). Both new methods were quicker and easier than the reference resin methods and of similar precision. The two measurements when combine...

The uncoupling of oxidative phosphorylation in mitochondrial preparations by thyroxine and its reversal are now well known (l-6). More recently we have shown that high levels of dietary magnesium completely prevent the uncoupling effect on heart mitochondria of thyroxine-fed animals, and partially overcome the growth inhibition caused by thyroxine. Thyroxine thus raises the magnesium requiremen...

1. Conversion of thyroxine into tri-iodothyronine and reverse tri-iodothyronine in intact cells was studied with isolated renal tubules prepared by collagenase digestion. 2. Conversion of thyroxine into tri-iodothyronine and reverse tri-iodothyronine increased progressively for at least 90 min. 3. Studies of tri-iodothyronine production from increasing amounts of thyroxine revealed that the thy...

Thyroxine in the thyroid gland is considered to be firmly built into the protein molecule, thyroglobulin (1). Only after the gland is hydrolyzed with fairly strong alkali does its thyroxine become readily extractable with butyl alcohol. The iodine which circulates in plasma, on the other hand, can be almost completely extracted with butyl alcohol without previous hydrolysis (2). Considerable ev...