scholarly journals Total over Free Thyroxine Ratio: Prediction of Thyroxine Binding Globulin

1982 ◽  
Vol 19 (2) ◽  
pp. 94-100
Author(s):  
Andries J Bakker ◽  
Ina Terpstra
Keyword(s):  
Thyroid Function ◽  
Binding Proteins ◽  
Free Thyroxine ◽  
The Other ◽  
Calculated Concentration ◽  
Thyroxine Binding Globulin ◽  
Total Thyroxine ◽  
Better Than

Both total thyroxine and free thyroxine concentrations are measured in the Immophase free thyroxine assay. These total and free thyroxine results allow a prediction of the accessory concentrations of thyroxine-binding globulin (TBG). Since abnormal concentrations of TBG often cause problems in the evaluation of thyroid function, we evaluated the possibility of predicting these abnormal values from total and free thyroxine results. Two ways of predicting abnormal concentrations of TBG were evaluated on statistical grounds. The first method, a simple total thyroxine/free thyroxine ratio, proved to be better than the second method, which corrected for the influence of the other thyroxine binding proteins (result: a calculated concentration of TBG). The total thyroxine/free thyroxine ratio predicts abnormally low TBG values, below a ratio of 4000 (certainty 45%) and abnormally high TBG values, above a ratio of 6400 (certainty 89%).

Pictorial reporting of multiple thyroid function results.

1976 ◽  
Vol 22 (10) ◽  
pp. 1562-1566
Author(s):  
R W Pain ◽  
B M Duncan
Keyword(s):  
Thyroid Function ◽  
Reporting System ◽  
Free Thyroxine ◽  
Thyroid Function Tests ◽  
Testing Procedures ◽  
Function Tests ◽  
Free Thyroxine Index ◽  
Total Thyroxine ◽  
Experience Difficulty

Abstract Clinicians experience difficulty in correctly interpreting the results of in vitro thyroid function tests in the presence of abnormalities of thyrobinding proteins or when results are borderline. This difficulty has been largely resolved in our laboratory by three innovations. First, the borderline areas for each of three routine tests of thyroid function (total thyroxine, thyrobinding index, and free thyroxine index) were accurately determined. Second, the results from this routine profile of three tests were displayed pictorially so as to produce patterns characteristic of various diagnostic situations, including euthyroidism in the presence of abnormalities of thyrobinding proteins. Third, interpretive comments and, in the case of borderline patterns, suggested further testing procedures were added to the report. Clinicians find the reporting system helpful and respond when additional tests are suggested. The system, operated manually at first, was later computerized.

INTERACTION BETWEEN THYROID HORMONE AND THYROXINE-BINDING PROTEINS IN THE EARLY NEONATAL PERIOD

1965 ◽  
Vol 32 (1) ◽  
pp. 45-57 ◽  
Author(s):  
A. ŚLEBODZIŃSKI
Keyword(s):  
Thyroid Hormone ◽  
Plasma Level ◽  
Binding Proteins ◽  
Neonatal Period ◽  
Free Thyroxine ◽  
Thyroxine Binding Globulin ◽  
Early Neonatal Period ◽  
Iodine Metabolism ◽  
Thyroid Metabolism

SUMMARY (1) The interaction between thyroid hormone and thyroxine-binding globulin (TBG) has been studied in 39 pigs from eight litters, aged from 12 hr. to 11 days. In addition, single observations were made on six batches of 42 pigs from 1 day to 6 months old and in five newborn sheep. (2) A rapid increase in the level of the unsaturated TBG capacity was found to occur from the 1st day after birth. (3) Continuous changes in the unsaturated TBG capacity resulted in a decline in the plasma level of free thyroxine and in a decrease in the uptake of [131I]triiodothyronine by erythrocytes. Equilibrium between the hormonal iodine metabolism and its blood carrier is reached at the end of the 1st week of life. (4) These findings suggest that in discussing thyroid metabolism in neonatal animals it is important to distinguish between the early neonatal adaptive period and the remainder of the period of thyroid hyperactivity. The physiological implications of the higher level of free thyroxine in the blood after birth for the adaptation to post-uterine life is discussed.

THE EFFECTS OF PHENYLBUTAZONE ON THYROID FUNCTION

1973 ◽  
Vol 72 (2) ◽  
pp. 257-264 ◽  
Author(s):  
M. O. Abiodun ◽  
R. Bird ◽  
C. W. H. Havard ◽  
N. K. Sood
Keyword(s):  
Thyroid Function ◽  
Significant Rise ◽  
Free Thyroxine ◽  
Continuous Treatment ◽  
Total Serum ◽  
Thyroid Function Tests ◽  
Tsh Secretion ◽  
Total Thyroxine ◽  
Pre Treatment ◽  
Tsh Levels

ABSTRACT It is known that phenylbutazone suppresses the thyroidal uptake of radioactive iodine and the serum level of protein-bound iodine (PBI) during the first week of treatment, with a return to normal values after 2 weeks of continuous treatment. Up till now the initial suppression of thyroid function has been presumed due to inhibition of TSH secretion. In the present study, total serum thyroxine and percentage dialysable thyroxine have been measured and the serum absolute free thyroxine concentration calculated in 12 patients before starting treatment with phenylbutazone orally, after 4 days of treatment and again after 14 days. Serum TSH was assayed in 10 of these patients before, and on the 4th day of treatment. Sera were assayed for TSH after 14 days on the drug in 6 patients. On the 4th day of treatment, the levels of total thyroxine had fallen but the levels of free thyroxine remained unchanged. TSH levels were also unaltered. By the 14th day of treatment, free thyroxine levels had fallen significantly below pre-treatment values but no significant rise in TSH could be demonstrated in the 6 patients studied. At no time was there a fall in TSH levels and we conclude that suppression of some thyroid function tests during the first week of treatment with phenylbutazone is due to direct inhibition of the gland by the drug.

scholarly journals Serum Free Thyroxine Concentrations in Subjects with High Circulating Levels of Thyroxine-Binding Globulin

1983 ◽  
Vol 20 (5) ◽  
pp. 285-288 ◽  
Author(s):  
K Ashwell ◽  
M R Hopton ◽  
J S Harrop
Keyword(s):  
Free Thyroxine ◽  
Control Group ◽  
Serum Free ◽  
Thyroxine Binding Globulin ◽  
Respective Control Group ◽  
Factor Ii ◽  
Total Thyroxine ◽  
Hormone Binding Protein ◽  
Circulating Levels ◽  
Serum Free Thyroxine

Serum free thyroxine (FT4) and thyroid hormone-binding protein concentrations were measured in pregnant women, stilboestrol-treated patients, and subjects with congenital thyroxine-binding-globulin (TBG) excess. In pregnant and stilboestrol-treated patients matched for TBG concentrations, serum FT4 concentrations measured by the Amerlex technique and by calculation, were reduced, as also was the total thyroxine (TT4)/TBG ratio. In congenital TBG excess Amerlex and calculated FT4 concentrations were normal whereas the TT4/TBG ratio was low. In contrast to the Amerlex method, FT4 concentrations by the Immophase procedure were normal in pregnant and stilboestrol-treated individuals and high in congenital TBG excess. We conclude that (i) reduced FT4 concentrations in pregnancy are related to an oestrogen effect rather than to some other pregnancy-associated factor, (ii) the TT4/TBG ratio gives a misleading indication of FT4 concentration in congenital TBG excess, and (iii) that when TBG concentrations are raised Immophase gives higher FT4 values than Amerlex or calculation when each is compared to FT4 values in their normal respective control group.

Is total thyroxine better than free thyroxine during pregnancy?

2014 ◽  
Vol 211 (2) ◽  
pp. 132.e1-132.e6 ◽  
Author(s):  
Karen L. Wilson ◽  
Brian M. Casey ◽  
Donald D. McIntire ◽  
F. Gary Cunningham
Keyword(s):  
Free Thyroxine ◽  
Total Thyroxine ◽  
Better Than

Is Free Thyroxine Accurately Measurable at Room Temperature?

1992 ◽  
Vol 38 (6) ◽  
pp. 880-886 ◽  
Author(s):  
H A Ross ◽  
T J Benraad
Keyword(s):  
Temperature Effect ◽  
Room Temperature ◽  
Free Thyroxine ◽  
The Other ◽  
Temperature Dependent ◽  
Thyroxine Binding Globulin ◽  
Total Binding ◽  
Relative Contribution ◽  
Back Titration ◽  
Titration Assay

Abstract Two recently developed two-step, or "back-titration" assay kits for free thyroxine (FT4)--one based on a europium-labeled derivative of T4, the other on conventional radiolabeled T4--were compared with both symmetrical dialysis and an indirect FT4 radioimmunoassay. Discrepancies between the two-step and the other two methods were observed, particularly in samples that had very low to zero thyroxine-binding globulin (TBG) content. In those instances the two-step methods gave values almost twice as high as the other methods. This effect could be largely reversed in one of the two-step assays and completely reversed in the other by performing the first incubation step at 37 degrees C rather than at room temperature, as prescribed by the manufacturers. When symmetrical dialysis is performed at both temperatures, FT4 at room temperature is about 40% of the amount determined at 37 degrees C, except in zero-TBG samples, where it averages almost 80% of the value at 37 degrees C. Moreover, we demonstrated that the affinity of TBG for T4 is much more temperature-dependent than the affinity of transthyretin and albumin for T4, so that the net temperature effect on the FT4 in a sample depends on the relative contribution of TBG to total binding. We conclude that performing FT4 assays at room temperature is principally incorrect and leads to falsely increased values when samples with very low TBG concentrations are analyzed.

Lowering effect of diphenylhydantoin on serum free thyroxine and thyroxine binding globulin (TBG)

1984 ◽  
Vol 105 (4) ◽  
pp. 477-481 ◽  
Author(s):  
Hitoshi Suzuki ◽  
Noriko Yamazaki ◽  
Yoshinobu Suzuki ◽  
Masaki Hiraiwa ◽  
Shin-ichi Shimoda ◽  
...  
Keyword(s):  
Thyroid Function ◽  
Serum Levels ◽  
Significant Negative Correlation ◽  
Free Thyroxine ◽  
Thyroid Function Tests ◽  
Duration Of Treatment ◽  
Function Tests ◽  
Total Triiodothyronine ◽  
Total Thyroxine ◽  
Anticonvulsant Treatment

Abstract. To evaluate the effect of anticonvulsants on serum levels of free thyroxine (FT4) and thyroxinebinding globulin (TBG), 32 patients with epilepsy receiving long-term anticonvulsant treatment (mean duration 81.8 ± 8.9 months) were employed in the present study. The serum levels of total thyroxine (TT4), total triiodothyronine (TT3), T3 resin uptake (T3U) and thyrotrophin (TSH) were also measured. Free thyroxine index (FT4I) was calculated from TT4 and T3U. Mean levels of these thyroid function tests were as follows: 5.52 ± 1.51 μg/dl (TT4), 1.16 ± 0.32 ng/dl (FT4), 101.5 ± 16.2 ng/dl (TT3), 27.5 ± 2.6% (T3U), 19.64 ± 3.97 μg/ml (TBG), 1.50 ± 0.36 (FT4I) and 2.21 ± 0.18 μU/ml (TSH). These values except for T3U and TSH were significantly lower than normal values (P < 0.01). Using correlation analysis, a significant dose-dependency (daily doses) was found between diphenylhydantoin (DPH) and TT4, FT4 and TBG. Other anticonvulsants (bartiturates, carbamazepine, primidone) or duration of treatment were not significantly correlated with thyroid function tests. Therefore serum levels of DPH were also measured in 19 out of 32 patients receiving anticonvulsant treatment. Significant negative correlation was found between serum levels of DPH and FT4 (r = −0.65) and DPH and TBG (r = −0.61).

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