Comparison of three simple methods for the assessment of `free' thyroid hormone

Abstract

SYNOPSIS A dialysis method for estimating 'free' thyroxine is compared with two indirect methods using the uptake of triiodothyronine by the red cells and by a Sephadex column. The three methods give results which correlate well and the Sephadex method is the simplest.The theoretical basis of such tests and their role in the assessment of thyroid status is briefly discussed.

Acute Depletion of the Hormonal-Iodine Stores From the Thyroid Gland After Birth in Lambs

“…For the assessment of variations in levels of the metabolically active form of the thyroidal hormone in blood, the [131I]tri-iodothyronine-binding coefficient (T3-BC) was measured according to Gimlette (1967). Analyses of PBI were performed in duplicate by the technique of Barker, Humprey & Soley (1951).…”

“…Studies based on the tri-iodothyronine-binding coefficient, which is proportional to free thyroxine (Gimlette, 1967), have been made in pigs and show that the free thyroxine in plasma reaches its highest value within 6-12 h after birth but then declines rapidly in spite of a high PBI level (Slebodzinski, 1965(Slebodzinski, , 1971). This variation in free thyroxine in the plasma occurs in unsuckled animals with a constant concen¬ tration of plasma proteins and thus might be directly related to changes in the secretory activity of the thyroid gland itself.…”