The influence of age and sex on the concentration of free thyroxin and on the free thyroxin/total thyroxin ratio was studied in 104 men and 89 women, ages 15 to 83 years. Free thyroxin gradually declined with age in men but not in women. In addition, sex- and age-related variations for free thyroxin were similar to those for total thyroxin and the two indirect assessments of free thyroxin: the ...

We undertook a prospective longitudinal study of thyroid function in 36 pregnant women. There were significant increases in thyroxin-binding globulin, thyrotropin, and triiodothyronine. Albumin, free thyroxin (measured by an analog and a nonanalog method), and the free thyroxin index were significantly decreased. Results for the free thyroxin methods were correlated with each other in each trim...

2. Meinhold H, Wenzel KW. Comparative methodological studies with six commercial FF4 kits. Nucl Compact 1985;16:317-20. 3. Ross HA. An indirect assay for serum free thyroxin (FF4) using monoclonal antibody coated tubes and radiolabeled thyroxin. Ibid., 1985;32:314-6. 4. Stockigt JR, Stevens V, White EL, Barlow JW. “Unbound analog” radioimmunoassays for free thyroxin measure the albuminbound hor...

BACKGROUND Although thyroxin therapy clearly is beneficial to children with frank hypothyroidism there is little data on the effects of thyroxin in children with compensated or subclinical hypothyroidism. The objective of this study was to determine the effect of thyroxin therapy on cognitive function in children with compensated hypothyroidism. The hypothesis was that thyroxin therapy would ch...

Although discrepancies have been reported between free thyroxin (fT4) in serum and actual thyrometabolic status, the concentration of free thyroid hormones in blood is thought to be an important determinant of the thyrometabolic status of patients. Therefore, the diagnostic value of fT4 measurement has been emphasized. This prompted us to evaluate the diagnostic significance of direct fT4 measu...

I compared values for the free thyroxin index derived from data obtained by four triiodothyronine-uptake kits for 93 euthyroid subjects with normal or altered thyroxin-binding globulin binding capacity. In addition, I devised a mathematical model of an "ideal" free thyroxin index. Only one uptake kit satisfactorily normalized values for the free thyroxin index in the increased thyroglobulin gro...

SUMMARY  The foliowing cardiac effects may be at­tributed to thyroxin:  1-Thyroxin augments all anaerobic pro­cesses in the body includ::ng the heart, and decreases the glycogen content of the heart ( 1, 2, 5, 27). The resistance of the heart to anoxia is increased in hyperthyroidism ( 25). 2- Thyroxin influences the cardiac weight and prevents cardiac atrophy (3, 8, 10, 11, 19, 20, 21, 30...

Three erythrocyte proteins, one identified as hemoglobin, bind thyroid hormones. Using a dextran/charcoal radioimmunoassay for thyroxin in dried blood spots, we demonstrate that such binding differs with the buffer used. Barbital, phosphate, and borate buffers significantly enhance the binding more than glycine and tris(hydroxymethyl)methylamine buffers. Binding is not affected by agents common...

We assessed the use of a dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) system to measure thyrotropin (thyroid-stimulating hormone, TSH) in routine clinical practice. The assay is simple and precise, with intrabatch CV of less than 10% down to 0.1 milli-int. unit/L. When compared with free thyroxin, total thyroxin, and triiodothyronine measurements in 142 patients, the present assa...

This is a procedure for rapidly identifying the three common abnormalities in binding of thyroxin by protein. After incubation with [125I]thyroxin, serum proteins are separated by electrophoresis on agarose gel and binding of thyroxin to the various protein fractions is determined after autoradiography. Quantitatively abnormal binding to albumin or prealbumin and thyroxin autoantibodies is easi...