Indirect estimation of thyroid hormone-binding proteins to calculate free thyroxine index: comparison of nonisotopic methods that use labeled thyroxine ("T-uptake")

1995 ◽  
Vol 41 (1) ◽  
pp. 41-47 ◽  
Author(s):  
J D Faix ◽  
H N Rosen ◽  
F R Velazquez
Keyword(s):  
Thyroid Hormone ◽  
Binding Proteins ◽  
Free Thyroxine ◽  
Reference Ranges ◽  
Hormone Binding ◽  
Free T4 ◽  
Nonthyroidal Illness ◽  
Free Thyroxine Index ◽  
Uptake Method ◽  
Hypothyroid Patients

Abstract There are many alternative ways of estimating free thyroxine (T4) when thyrotropin screening results are abnormal. In addition to free T4 immunoassays, the menu of most automated immunoassay instruments includes a nonisotopic version of the original triiodothyronine (T3)-uptake assay called "T-uptake." We evaluated the ability of five such assays (Access, ES-300, IMx, Magnum Opus, and Stratus) to accurately estimate the free thyroxine index (FTI) in euthyroid, hyperthyroid, and hypothyroid patients with abnormal concentrations of thyroid hormone-binding proteins, and in patients with nonthyroidal illness. For comparison, we calculated a similar FTI, using either T3-uptake or direct measurement of thyroxine-binding globulin (TBG). Euthyroid reference ranges were comparable. Of euthyroid patients with increased TBG, 12-32% and 5-20% had increased or suppressed FTI, respectively, depending on the T-uptake method used. Except for IMx, 6-35% of hypothyroid patients with increased TBG had inappropriately increased FTI. Patients with nonthyroidal illness had comparable results regardless of the method used, and T-uptake methods were variably affected by known inhibitors of thyroid hormone binding. The most reliable T-uptake method appeared to be the IMx, which, despite claims that it measures all thyroid hormone-binding proteins, correlated best with TBG concentrations.

Interrelationships among body mass, thyrotropin, thyroid hormones, and thyroid-hormone binding proteins in healthy 70-year-old men.

1984 ◽  
Vol 30 (5) ◽  
pp. 681-686 ◽  
Author(s):  
S Edén ◽  
R Jagenburg ◽  
G Lindstedt ◽  
P A Lundberg ◽  
D Mellström
Keyword(s):  
Body Mass Index ◽  
Thyroid Hormone ◽  
Body Mass ◽  
Binding Proteins ◽  
Dominant Role ◽  
Negative Relationship ◽  
Feedback Regulation ◽  
Hormone Binding ◽  
Free T4 ◽  
Old Men

Abstract In a previous study of a representative population of 460 men of age 70, we found that the free thyroxin (free T4) concentration was negatively correlated to body mass. In the present study we analyzed other indicators of thyroid function in relation to body mass and body mass index in 181 individuals without any disease or medication influencing thyroidal homeostasis or body mass. There was a significant negative relationship between body mass and body mass index and free T4, total T4, and 3,3',5'-triiodothyronine (rT3). Thus, individuals with high body mass normally had lower circulating concentrations of these hormones than lean individuals, whereas there was no such relationship for thyrotropin or 3,5,3'-triiodothyronine (T3). The thyroid-hormone binding proteins (thyroxin-binding globulin, prealbumin, and albumin) did not correlate with body mass or body mass index. As expected, thyroxin-binding globulin correlated with T4, T3, and rT3, but not with free T4 or thyrotropin. Concentrations of serum albumin correlated with T3 and rT3 concentrations but not with free T4, T4, or thyrotropin concentrations. Thyrotropin concentrations correlated negatively with free T4, T4, and rT3, but not with T3, indicating that circulating T4 plays the dominant role in feedback regulation of thyrotropin in healthy individuals.

EFFECT OF CLOMIFENE ON THYROID FUNCTION IN NORMAL MEN

1979 ◽  
Vol 90 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Ulla Feldt-Rasmussen ◽  
Axel P. Lange ◽  
John Date ◽  
Mogens Kern Hansen
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Function ◽  
Binding Proteins ◽  
Serum Concentrations ◽  
Hormone Binding ◽  
Free Thyroxine Index ◽  
Group 2 ◽  
Uptake Test ◽  
Normal Men ◽  
Group 1

ABSTRACT To study the effect on thyroid function 100 mg of clomifene citrate was given once a day to two groups of healthy male volunteers for 5 and 12 consecutive days, respectively. In both groups serum concentrations of TSH, thyroxine, triiodothyronine, T3 resin uptake test and thyroid hormone binding proteins were measured before, during and after oral administration of clomifene. The effect of clomifene treatment was evaluated in Group 1 by means of serum FSH and LH measurements. Further in Group 2 the serum TSH response to iv TRH (200 μg) was also investigated. The mean per cent elevations in serum concentrations of FSH and LH were 145 and 200, respectively. In Group 1 a small but statistically significant decrease within reference limits in triiodothyronine (P < 0.01) and free thyroxine index (P < 0.02) was found on day 4 of clomifene. On day 5 a slight increase in TSH was observed (P < 0.05). In Group 2 the response of TSH to TRH showed a non-significant increase after 5 days and a significant increase (P < 0.01) after 12 days of clomifene. Eight days after discontinuation of the drug the response was restored to normal. No changes in the thyroid hormone binding proteins in serum could be demonstrated. Though the observed changes were slight, they indicate that clomifene exerts an influence directly on the thyroid function.

Uptake of thyroxine by the perfused rat liver: implications for the free hormone hypothesis

1988 ◽  
Vol 255 (2) ◽  
pp. E110-E119 ◽  
Author(s):  
C. M. Mendel ◽  
R. R. Cavalieri ◽  
R. A. Weisiger
Keyword(s):  
Thyroid Hormone ◽  
Rat Liver ◽  
Rate Constants ◽  
Binding Proteins ◽  
Human Thyroid ◽  
Plasma Binding ◽  
Perfused Rat Liver ◽  
Hormone Binding ◽  
Free T4 ◽  
Hepatic Cells

To investigate the mechanism by which thyroxine (T4) in plasma enters hepatic cells, we measured the rate constants for uptake of free T4 by the perfused rat liver and for dissociation of T4 from its plasma binding proteins. Quantitative autoradiography of liver lobules after perfusion with [125I]T4 indicated an apparent rat constant for removal of free T4 from the sinusoids of at least 1.1 +/- 0.2 s-1. Single-pass extraction of T4 from human serum was 10.6 +/- 1.7% at physiological flow rates (1 ml.min-1.g liver-1). Rate constants for dissociation of T4 from plasma binding proteins at 37 degrees C (determined by rapid filtration) were 0.017 +/- 0.002 s-1 for human thyroid hormone-binding globulin, 0.080 +/- 0.015 s-1 for human thyroid hormone-binding prealbumin, and greater than 0.5 s-1 for human albumin. To investigate the factors that determine the concentration of T4 within hepatic cells, we analyzed the above data together with data reported in the literature on the equilibrium-binding constants and the rate constant for cellular metabolism of T4. Analysis of all of these data using a previously published mathematical model leads to the following conclusions for the physiological state: 1) metabolism, not uptake, is rate limiting to removal of T4 from plasma by the liver; 2) binding equilibrium is present in the intrahepatic plasma; 3) intracellular T4 is in equilibrium with the free T4 pool in plasma (and maintenance of this equilibrium may be an important function of plasma thyroid hormone-binding proteins); and 4) the concentration of T4 within the liver is proportional to the concentration of free T4 in the plasma. Our data do not allow us to determine definitively whether hepatic uptake of T4 occurs only from the free T4 pool in plasma or also from the protein-bound pool by interaction of one or more of the binding proteins with the liver cell. However, mathematical analysis indicates that this distinction is irrelevant to steady-state intracellular hormone concentrations when equilibrium exists between the plasma and cytosolic pools of hormone.

ENDOCRINE CHANGES BEFORE AND AFTER THE MENARCHE

1973 ◽  
Vol 74 (4) ◽  
pp. 685-694 ◽  
Author(s):  
B.-A. Lamberg ◽  
R.-L. Kantero ◽  
P. Saarinen ◽  
O. Widholm
Keyword(s):  
Binding Proteins ◽  
Maturation Process ◽  
Hormone Binding ◽  
Maximal Level ◽  
Continuous Increase ◽  
Mean Values ◽  
Thyroxine Binding Globulin ◽  
Before And After ◽  
Free Thyroxine Index ◽  
Level 1

ABSTRACT In an endocrine survey of healthy girls aged 8 to 20 years before and after the menarche, the serum thyroxine (T4), uptake of triiodothyronine by Sephadex (T3U), and the binding capacities of thyroxine binding globulin (TBG) and pre-albumin (TBPA) were measured, and a free thyroxine index (FTI = T4 × T3U) was calculated. The subjects were grouped according to skeletal age (SA) until the menarche and after this in the post-menarcheal age (PMA), expressed in years. T4 and FTI increased concomitantly and reached peak values of 8.40 μg/100 ml and 8.40, respectively, at 2–3 years PMA. The corresponding mean values for post-menarcheal girls (7.74 μg/100 ml and 7.51) differed statistically significantly from the means before the menarche (7.03 μg/ 100 ml and 6.75). The TBG remained virtually unchanged during the whole period, whereas the TBPA showed a continuous increase and reached a maximal level 1–2 years after the menarche. The maturation process in girls in some way involves an increase in the total and free T4 level which is not dependent on hormone binding proteins.

scholarly journals Studies on Cytosol Thyroid Hormone Binding Proteins in Rat Liver

1987 ◽  
Vol 63 (1) ◽  
pp. 69-76
Author(s):  
Masataka NANNO ◽  
Hirotoshi NAKAMURA ◽  
Satoshi HAMADA ◽  
Teruya YOSHIMI ◽  
Hiroo IMURA ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Rat Liver ◽  
Binding Proteins ◽  
Hormone Binding

Post-natal thyroid function in low birth weight infants; a longitudinal assessment of free thyroxine and thyroid hormone binding globulin

1985 ◽  
Vol 110 (1) ◽  
pp. 56-60 ◽  
Author(s):  
Takeki Hirano ◽  
Jaideep Singh ◽  
Gopal Srinivasan ◽  
Rosita Pildes
Keyword(s):  
Body Weight ◽  
Birth Weight ◽  
Thyroid Hormone ◽  
Low Birth Weight ◽  
Free Thyroxine ◽  
Extremely Low Birth Weight ◽  
Longitudinal Assessment ◽  
Hormone Binding ◽  
Low Birth Weight Infants ◽  
Term Infants

Abstract. Because the concentrations of serum free thyroxine (FT4) and thyroid hormone binding globulin (TBG) have not been fully evaluated in preterm infants at the immediate post-natal period, we studied the longitudinal changes of serum FT4 and TBG, along with thyroxine (T4) and thyroid stimulating hormone (TSH), at birth (cord blood), 2 days, 1 week and 2 weeks of age in 7 infants with birth body weight ≦ 1000 g, 7 infants with body weight 1001 to 1350 g, 11 infants with body weight 1351 to 2499 g, and 11 full-term infants. Free T4 concentrations were measured by Corning Medical radio-immunoassay (RIA) kit. The infants with extremely low birth weight (ELBW) (body weight ≦ 1000 g) showed precipitous declines of total T4 and, to a lesser extent, of FT4 concentrations at 1 and 2 weeks of age. These post-natal T4 and FT4 decreases in ELBW neonates have not previously been reported. The clinical significance of this finding remains, speculative, but it may be due to metabolic or nutritional problems related to extreme prematurity itself. This study suggests that measurement of FT4 is a useful adjunct to the assessment of ELBW infants with wery low T4 values, if done between 1 to 2 weeks af age, and could be used as a primary hypothyroid screening tool instead of T4 measurements, provided that an FT4 assay is developed that uses the elute of blood spotted on filter paper.

scholarly journals Studies on Cytosol Thyroid Hormone Binding Proteins in Rat Liver

1987 ◽  
Vol 63 (1) ◽  
pp. 77-86
Author(s):  
Masataka NANNO ◽  
Hirotoshi NAKAMURA ◽  
Satoshi HAMADA ◽  
Teruya YOSHIMI ◽  
Hiroo IMURA ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Rat Liver ◽  
Binding Proteins ◽  
Hormone Binding
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