The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Arthur J. Prange - One of the best experts on this subject based on the ideXlab platform.
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effects of thyroxine as compared with thyroxine plus Triiodothyronine in patients with hypothyroidism
The New England Journal of Medicine, 1999Co-Authors: Robertas Bunevicius, Gintautas Kazanavicius, R Zalinkevicius, Arthur J. PrangeAbstract:A BSTRACT Background Patients with hypothyroidism are usually treated with thyroxine (levothyroxine) only, although both thyroxine and Triiodothyronine are secreted by the normal thyroid gland. Whether thyroid secretion of Triiodothyronine is physiologically important is unknown. Methods We compared the effects of thyroxine alone with those of thyroxine plus Triiodothyronine (liothyronine) in 33 patients with hypothyroidism. Each patient was studied for two five-week periods. During one period, the patient received his or her usual dose of thyroxine. During the other, the patient received a regimen in which 50 µg of the usual dose of thyroxine was replaced by 12.5 µg of Triiodothyronine. The order in which each patient received the two treatments was randomized. Biochemical, physiologic, and psychological tests were performed at the end of each treatment period. Results The patients had lower serum free and total thyroxine concentrations and higher serum total Triiodothyronine concentrations after treatment with thyroxine plus Triiodothyronine than after thyroxine alone, whereas the serum thyrotropin concentrations were similar after both treatments. Among 17 scores on tests of cognitive performance and assessments of mood, 6 were better or closer to normal after treatment with thyroxine plus Triiodothyronine. Similarly, among 15 visual-analogue scales used to indicate mood and physical status, the results for 10 were significantly better after treatment with thyroxine plus Triiodothyronine. The pulse rate and serum sex hormone–binding globulin concentrations were slightly higher after treatment with thyroxine plus Triiodothyronine, but blood pressure, serum lipid concentrations, and the results of neurophysiologic tests were similar after the two treatments. Conclusions In patients with hypothyroidism, partial substitution of Triiodothyronine for thyroxine may improve mood and neuropsychological function; this finding suggests a specific effect of the Triiodothyronine normally secreted by the thyroid gland. (N Engl J Med 1999;340:424-9.)
Heather M. Stapleton - One of the best experts on this subject based on the ideXlab platform.
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analysis of thyroid hormones in serum by liquid chromatography tandem mass spectrometry
Analytical and Bioanalytical Chemistry, 2010Co-Authors: Dongli Wang, Heather M. StapletonAbstract:Thyroid hormones are essential hormones for regulating growth and development in humans and wildlife. Methods to monitor precise and low levels of these hormones in serum and tissues are needed to assess overall health, whether from disease considerations or possibly from environmental contaminant exposures. Common and routine methods typically rely upon radioimmunoassays, which can be expensive, and typically only measure thyroxine and 3,3′,5-triidothyronine, which can be a limitation in fully evaluating impacts on thyroid regulation. In this study we developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for the simultaneous analysis of five thyroid hormones—thyroxine, 3,3′,5-triidothyronine, 3,3′,5′-Triiodothyronine, 3,3′-diiodothyronine, and 3,5-diiodothyronine—in serum samples. The LC-MS/MS parameters were optimized and calibrated over a wide concentration range (1.0–500 ng/mL) with on-column detection limits of 1.5–7.0 pg. With use of spiked bovine serum samples, the mean method recoveries were calculated to be 81.3–111.9% with relative standard deviations of 1.2–9.6% at spiking levels ranging from 10 to 100 ng/mL. This method was compared with measurements made by standard radioimmunoassays and with measurements made in a serum Standard Reference Material (SRM 1951b). Development of this method expands the capacity to measure thyroid hormones by including a larger suite of thyroid hormones, and has promising applications for measuring catabolism of thyroid hormones in vitro.
F E Wilson - One of the best experts on this subject based on the ideXlab platform.
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a test of the hypothesis that t3 is the seasonality thyroid hormone in american tree sparrows spizella arborea intracerebroventricular infusion of iopanoic acid an inhibitor of t3 synthesis and degradation
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2001Co-Authors: F E WilsonAbstract:This study tested the hypothesis that L-3,5,3′-Triiodothyronine (T3) is the bioactive "seasonality" thyroid hormone in American tree sparrows (Spizella arborea). The experimental approach coupled thyroid hormone replacement therapy after radiothyroidectomy with photostimulation and intracerebroventricular infusion of iopanoic acid, an inhibitor of L-3,5,3′-Triiodothyronine synthesis and degradation. Endpoints were testis length, molt score, and hypothalamic content of chicken gonadotropin-releasing hormone I. The hypothesis predicts that thyroidectomized male tree sparrows moved to long days and given thyroxine in combination with iopanoic acid will lack L-3,5,3′-Triiodothyronine and so will not express thyroid hormone-dependent photoperiodic testicular growth (a vernal component of seasonality) and photorefractoriness or postnuptial molt (autumnal components of seasonality). It further predicts that iopanoic acid will enhance the efficacy of L-3,5,3′-Triiodothyronine and so will facilitate the expression of seasonality in thyroidectomized males given L-3,5,3′-Triiodothyronine replacement therapy. Iopanoic acid had no significant effect on any component of seasonality in thyroid-intact males given vehicle, or in thyroidectomized males given thyroxine or L-3,5,3′-Triiodothyronine. Thyroid-intact males, as well as thyroidectomized males infused with thyroxine alone, commonly expressed all components of seasonality. Thyroidectomized males given L-3,5,3′-Triiodothyronine alone exhibited photoperiodic testicular growth, but did not become photorefractory or initiate molt. While these results confirm that thyroid hormone acts centrally to program American tree sparrows for seasonality, they do not support the hypothesis that L-3,5,3′-Triiodothyronine is the bioactive "seasonality" thyroid hormone, and they challenge the view that thyroxine is merely a prohormone.
Robertas Bunevicius - One of the best experts on this subject based on the ideXlab platform.
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effects of thyroxine as compared with thyroxine plus Triiodothyronine in patients with hypothyroidism
The New England Journal of Medicine, 1999Co-Authors: Robertas Bunevicius, Gintautas Kazanavicius, R Zalinkevicius, Arthur J. PrangeAbstract:A BSTRACT Background Patients with hypothyroidism are usually treated with thyroxine (levothyroxine) only, although both thyroxine and Triiodothyronine are secreted by the normal thyroid gland. Whether thyroid secretion of Triiodothyronine is physiologically important is unknown. Methods We compared the effects of thyroxine alone with those of thyroxine plus Triiodothyronine (liothyronine) in 33 patients with hypothyroidism. Each patient was studied for two five-week periods. During one period, the patient received his or her usual dose of thyroxine. During the other, the patient received a regimen in which 50 µg of the usual dose of thyroxine was replaced by 12.5 µg of Triiodothyronine. The order in which each patient received the two treatments was randomized. Biochemical, physiologic, and psychological tests were performed at the end of each treatment period. Results The patients had lower serum free and total thyroxine concentrations and higher serum total Triiodothyronine concentrations after treatment with thyroxine plus Triiodothyronine than after thyroxine alone, whereas the serum thyrotropin concentrations were similar after both treatments. Among 17 scores on tests of cognitive performance and assessments of mood, 6 were better or closer to normal after treatment with thyroxine plus Triiodothyronine. Similarly, among 15 visual-analogue scales used to indicate mood and physical status, the results for 10 were significantly better after treatment with thyroxine plus Triiodothyronine. The pulse rate and serum sex hormone–binding globulin concentrations were slightly higher after treatment with thyroxine plus Triiodothyronine, but blood pressure, serum lipid concentrations, and the results of neurophysiologic tests were similar after the two treatments. Conclusions In patients with hypothyroidism, partial substitution of Triiodothyronine for thyroxine may improve mood and neuropsychological function; this finding suggests a specific effect of the Triiodothyronine normally secreted by the thyroid gland. (N Engl J Med 1999;340:424-9.)
Dongli Wang - One of the best experts on this subject based on the ideXlab platform.
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analysis of thyroid hormones in serum by liquid chromatography tandem mass spectrometry
Analytical and Bioanalytical Chemistry, 2010Co-Authors: Dongli Wang, Heather M. StapletonAbstract:Thyroid hormones are essential hormones for regulating growth and development in humans and wildlife. Methods to monitor precise and low levels of these hormones in serum and tissues are needed to assess overall health, whether from disease considerations or possibly from environmental contaminant exposures. Common and routine methods typically rely upon radioimmunoassays, which can be expensive, and typically only measure thyroxine and 3,3′,5-triidothyronine, which can be a limitation in fully evaluating impacts on thyroid regulation. In this study we developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for the simultaneous analysis of five thyroid hormones—thyroxine, 3,3′,5-triidothyronine, 3,3′,5′-Triiodothyronine, 3,3′-diiodothyronine, and 3,5-diiodothyronine—in serum samples. The LC-MS/MS parameters were optimized and calibrated over a wide concentration range (1.0–500 ng/mL) with on-column detection limits of 1.5–7.0 pg. With use of spiked bovine serum samples, the mean method recoveries were calculated to be 81.3–111.9% with relative standard deviations of 1.2–9.6% at spiking levels ranging from 10 to 100 ng/mL. This method was compared with measurements made by standard radioimmunoassays and with measurements made in a serum Standard Reference Material (SRM 1951b). Development of this method expands the capacity to measure thyroid hormones by including a larger suite of thyroid hormones, and has promising applications for measuring catabolism of thyroid hormones in vitro.
