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Testosterone, androstenedione, cortisol, triiodothyronine and thyroxine hormonal profile in neonate male buffaloes

Ohashi, O. M.; Oba, E.; Nogueira, JR
Fonte: Arquivo Brasileiro Medicina Veterinaria Zootecnia Publicador: Arquivo Brasileiro Medicina Veterinaria Zootecnia
Tipo: Artigo de Revista Científica Formato: 189-196
ENG
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56.08%
Basic aspects of the hormonal profile of five hormones were studied in neonate male buffaloes. The level of testosterone (T), androstenedione (A), cortisol (C), triiodothyronine (T3) and thyroxine (T4) were determined during the period of 1-6, 7-8, - 9-12, 24, 48, 72 and 96 hours after parturition, using RIA solid phase technique. All hormones studied presented high levels in the neonate animals. The T and A levels were high in the first 1-6 hours post-partum, being 99.6+/-66.6 and 1,301.4+/-887.7 pg/ml, respectively. The T decreased sharply to basal levels (below the analysis limit of detection) within 24 hours while the A reached the basal level within 48 hours with 348.0+/-279.4pg/ml. The C and T4 levels were also high in the first 24-48 hours, which levels were 5.0+/-3.2 and 11.1+/-2.6 mu g/ml, respectively, decreasing gradually and significantly (P<0.01) until 96 hours post-partum, when they approached the basal levels (1.2+/-1.5 and 7.2+/-2.7 mu g/ml, respectively). The concentration of T3 remained elevated during the entire period of sample collection with little variation (P>0.05), with levels of 328.6+/-130.8 and 294.5+/-134.9ng/dl, respectively during 1-6 hours and 96 hours after parturition.

Metabolic disturbances in male broilers of different strains. 2. Relationship between the thyroid and somatotropic axes with growth rate and mortality

Gonzales, Elisabeth; Buyse, Johan; Sartori, José Roberto; Loddi, Maria Marta; Decuypere, Eddy
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 516-521
ENG
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46.16%
Seven male broiler strains (Arbor Acres, Avian Farms, Cobb-500, Hubbard-Peterson, ISA, Naked Neck, and Ross) were compared for their growth rate, feed efficiency, and mortality due to sudden death and ascites. In addition, weekly plasma levels of thyroid hormones [3,3′,5-triiodothyronine (T3) thyroxine (T4), T3: T4 ratio, growth hormone (GH), and insulin-like growth factor-I (IGF-I)] were determined. The highly productive, commercial strains were very similar in their endocrine profiles but differed markedly from the Naked Neck chickens. Naked Neck chickens were characterized by higher plasma T3 and lower T4 levels at similar ages as well as when compared on the same body weight basis. The present findings support the hypothesis that the slightly hypothyroid state of high productive broilers renders them more sensitive to metabolic disorders. Naked Neck chickens also had higher plasma GH levels than those of their age-matched commercial broilers. The coefficient of variation for GH was highest for Naked Neck chickens, which is indicative for an amplified GH burst amplitude. It may be stated that changes in plasma thyroid hormone concentration in indirect response to selection for low feed conversion and fast growth may be causatively linked to susceptibility for metabolic disturbances such as sudden death syndrome and ascites.

Effects of storage time on incubating egg gas pressure, thyroid hormones, and corticosterone levels in embryos and on their hatching parameters

Tona, K.; Malheiros, R. D.; Bamelis, F.; Careghi, C.; Moraes, V. M B; Onagbesan, O.; Decuypere, E.; Bruggeman, V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 840-845
ENG
Relevância na Pesquisa
46.16%
Incubating eggs (1,800 total) produced by a commercial flock of Cobb broiler breeders were used to determine the effects of storage duration (3 and 18 d) on gas partial pressure, thyroid hormones, and hatching parameters. Partial pressure of oxygen (pO2) and carbon dioxide (pCO2) were measured on d 18 and at internal pipping (IP) during incubation. Blood samples were collected for determination of triiodothyronine (T3), thyroxine (T4), and corticosterone concentrations in the embryos at IP and in newly hatched chicks. From 464 to 510 h of incubation, eggs were checked individually every 2 h to determine the timing and duration of IP, external pipping (EP), and total hatching time. At 18 d of incubation and at IP, pCO2 was greater in air cell of eggs stored for 3 d compared to those stored for 18 d (P < 0.05), but pO2 was greater in eggs stored for 18 d. At IP, T3 and corticosterone levels were higher in plasma of the embryos of eggs stored for 3 d compared to those stored for 18 d, but it was the reverse in newly hatched chicks (P < 0.05). Embryos from eggs stored for 18 d required more time to complete IP compared to embryos of eggs stored for only 3 d (P < 0.05), whereas the duration of EP was not affected by storage. The overall longer incubation was...

High resolution crystal structures of piscine transthyretin reveal different binding modes for triiodothyronine and thyroxine

Eneqvist, Therese; Lundberg, Erik; Karlsson, Anders; Huang, Shenghua; Santos, Cecília R. A.; Power, Deborah; Sauer-Eriksson, A. Elisabeth
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Publicado em //2004 ENG
Relevância na Pesquisa
55.93%
Transthyretin (TTR) is an extracellular transport protein involved in the distribution of thyroid hormones and vitamin A. So far, TTR has only been found in vertebrates, of which piscine TTR displays the lowest sequence identity with human TTR (47%). Human and piscine TTR bind both thyroid hormones 3,5,3 -triiodo- L-thyronine (T3) and 3,5,3 ,5 -tetraiodo-L-thyronine (thyroxine, T4). Human TTR has higher affinity for T4 than T3, whereas the reverse holds for piscine TTR. X-ray structures of Sparus aurata (sea bream) TTR have been determined as the apo-protein at 1.75 Å resolution and bound to ligands T3 and T4, both at 1.9 Å resolution. The apo structure is similar to human TTR with structural changes only at -strand D. This strand forms an extended loop conformation similar to the one in chicken TTR. The piscine TTR T4 complex shows the T4-binding site to be similar but not identical to human TTR, whereas the TTR T3 complex shows the I3 halogen situated at the site normally occupied by the hydroxyl group of T4. The significantly wider entrance of the hormone- binding channel in sea bream TTR, in combination with its narrower cavity, provides a structural explanation for the different binding affinities of human and piscine TTR to T3 and T4.

Effect of thyroid-suppressive doses of triiodothyronine on thyroxine turnover and on the free thyroxine fraction

Schussler, George C.; Vance, Vernon K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1968 EN
Relevância na Pesquisa
46.43%
The relationship between free thyroxine concentration and thyroxine turnover was studied during thyroid suppression with triiodothyronine. Although there was some increase in the proportion of serum thyroxine bound to thyroxine-binding globulin, the ratio of ultrafilterable to protein-bound hormone was not significantly affected. The fractional disappearance rate of thyroxine increased from an average control value of 11.47%/day to 14.72%/day. Because of contraction of the thyroxine distribution space the clearance of thyroxine was less markedly affected, increasing from 1.37 to 1.56 liters/day. Since the ratio of thyroxine turnover to free thyroxine concentration, i.e., the free thyroxine clearance, increased proportionately (4.79-5.55 liters × 103/day) we conclude that triiodothyronine stimulates thyroxine clearance by a mechanism that is independent of effects on free thyroxine concentration.

Triiodothyronine and Thyroxine in Hyperthyroidism COMPARISON OF THE ACUTE CHANGES DURING THERAPY WITH ANTITHYROID AGENTS

Abuid, J.; Larsen, P. R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1974 EN
Relevância na Pesquisa
56.09%
In 66 untreated patients with hyperthyroidism, serum triiodothyronine (T3) and thyroxine (T4) concentrations were measured by immunoassay. The mean T3 level was 478±28 ng/100 ml (all values mean±SEM) and the T4 was 20.6±0.6 μg/100 ml. The serum T4/T3 ratio by weight was 48±2 as opposed to a value of 71±3 in euthyroid adults. There was a significant inverse correlation of the T4/T3 ratios with serum T3 (r=0.77; P<0.01) but not with serum T4(r=0.21). These results suggested that relative overproduction of T3 is consistently present in patients with hyperthyroidism.

Triiodothyronine and Thyroxine in the Serum and Thyroid Glands of Iodine-Deficient Rats

Abrams, G. M.; Larsen, P. R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1973 EN
Relevância na Pesquisa
56.08%
Triiodothyronine (T3) and thyroxine (T4) were measured by immunoassay in the serum and thyroid hydrolysates of control (group A), mildly iodine-deficient (group B), and severely iodine-deficient rats (group C). These results were correlated with changes in thyroidal weight, 131I uptake and 127I content as well as with the distribution of 131I in Pronase digests of the thyroid. There was a progressive increase in thyroid weight and 131I uptake at 24 h with decrease in iodine intake. The 127I content of the thyroids of the group B animals was 44% and that of the group C animals 2% of that in group A. The mean labeled monoiodotyrosine/diiodotyrosine (MIT/DIT) and T3/T4 ratios in group A were 0.42±0.07 (SD) and 0.12±0.01, 0.59±0.06 and 0.11±0.03 in group B, and 2.0±0.3 and 1.8±0.9 in the group thyroid digests.

Contributions of Plasma Triiodothyronine and Local Thyroxine Monodeiodination to Triiodothyronine to Nuclear Triiodothyronine Receptor Saturation in Pituitary, Liver, and Kidney of Hypothyroid Rats: FURTHER EVIDENCE RELATING SATURATION OF PITUITARY NUCLEAR TRIIODOTHYRONINE RECEPTORS AND THE ACUTE INHIBITION OF THYROID-STIMULATING HORMONE RELEASE

Silva, J. E.; Larsen, P. R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1978 EN
Relevância na Pesquisa
46.25%
Injections of triiodothyronine (T3) and thyroxine (T4) into chronically hypothyroid rats were used to evaluate the contribution of intracellular T4 to T3 conversion to nuclear T3 in pituitary, liver, and kidney, and to correlate the occupancy of pituitary nuclear T3 receptors with inhibition of thyroid-stimulating hormone (TSH) release. Injection of a combination of 70 ng T3 and 400 ng T4/100 g body wt resulted in plasma T3 concentrations of 45±7 ng/dl (mean±SD) and 3.0±0.4 μg/dl T4 3 h later. At that plasma T3 level, the contribution of plasma T3 to the nuclear receptor sites resulted in saturation of 34±7% for pituitary, 27±5% for liver, and 33±2% for kidney. In addition to the T3 derived from plasma T3, there was additional T3 derived from intracellular monodeiodination of T4 in all three tissues that resulted in total nuclear occupancy (as percent saturation) of 58±11% (pituitary), 36±8% (liver), and 41±11% (kidney), respectively. The percent contribution of T3 derived from cellular T4 added 41% of the total nuclear T3 in the pituitary which was significantly higher than the contribution of this source in the liver (24%) or the kidney (19%). 3 h after intravenous injection of increasing doses of T3, the plasma T3 concentration correlated well with both the change in TSH and the nuclear occupancy...

Thyroid Hormone Action in Cell Culture: Demonstration of Nuclear Receptors in Intact Cells and Isolated Nuclei

Samuels, Herbert H.; Tsai, Jir S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1973 EN
Relevância na Pesquisa
46.51%
Triiodothyronine and thyroxine induce a 3-fold increase in the rate of growth of GH1 cells in culture. To study further the action of these hormones, we examined the binding of [125I]triiodothyronine and purified [125I]thyroxine to cellular fractions after incubation with intact cells in serum-free medium. High-affinity, low-capacity binding sites for the hormones were demonstrated in nuclear but not in mitochondrial or cytosol fractions. Chromatographic analysis of the bound nuclear radioactivity from cells incubated with [125I]thyroxine demonstrated 97% thyroxine, 1% iodide, and 1% triiodothyronine. Apparent equilibrium dissociation constants, determined by Scatchard analysis, were 29 pM for triidothyronine and 260 pM for thyroxine. The maximal binding capacity was identical for both hormones, with about 5000 sites per cell nucleus. [125I]Thyroxine binding was competitively inhibited by triiodothyronine. These data suggest that triiodothyronine and thyroxine interact with identical nuclear receptors, and that conversion of thyroxine to triiodothyronine may not be a prerequisite for biologic activity. Similar high-affinity, low-capacity nuclear binding sites were also demonstrated by incubation of [125I]triidothyronine directly with isolated nuclei. Incubation of cells with increasing concentrations of nonradioactive triidothyronine results in a subsequent increase in binding when [125I]triiodothyronine is then incubated directly with isolated nuclei. This result suggests that nuclear receptors are not fixed...

Reduced serum free thyroxine concentration in postmenopausal women receiving oestrogen treatment.

Abdalla, H I; Hart, D M; Beastall, G H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 10/03/1984 EN
Relevância na Pesquisa
46.12%
Thyroid hormone state was assessed in a group of postmenopausal women who had received long term treatment with oestrogen. Serum concentrations of total thyroxine, triiodothyronine, and thyroxine binding globulin were raised compared with those in a control group given placebo; serum concentrations of thyroid stimulating hormone did not differ between the groups. Oestrogen treatment resulted in a significant decrease in the serum free thyroxine concentration and in the ratio of thyroxine to thyroxine binding globulin, which supports the view that oestrogen is the causative factor of the physiological reduction in free thyroid hormone during pregnancy.

NON-TOXIC GOITER TREATMENT WITH I-TRIIODOTHYRONINE AND I-THYROXINE

Fawell, William N.; Catz, Boris
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1963 EN
Relevância na Pesquisa
46.3%
Twenty-one patients with goiters—four diffuse and 17 nodular—were treated with I-triiodothyronine and I-thyroxine in doses to tolerance. The four diffuse goiters were barely palpable at the end of the treatment. The average dose of I-triiodothyronine required was 100 mcg. per day. The average dose of I-thyroxine was 0.3 mg. per day. Of the 17 multinodular goiters, 11 showed at least a 50 per cent reduction in size. The average dose of I-triiodothyronine used was 125 mcg. In six cases the gland did not change in size; in three of the six the lesion was diagnosed, at operation, as microfollicular and macrofollicular colloid goiter.

Dietary l-Arginine Supplementation Reduces White Fat Gain and Enhances Skeletal Muscle and Brown Fat Masses in Diet-Induced Obese Rats1–3

Jobgen, Wenjuan; Meininger, Cynthia J.; Jobgen, Scott C.; Li, Peng; Lee, Mi-Jeong; Smith, Stephen B.; Spencer, Thomas E.; Fried, Susan K.; Wu, Guoyao
Fonte: American Society for Nutrition Publicador: American Society for Nutrition
Tipo: Artigo de Revista Científica
Publicado em /02/2009 EN
Relevância na Pesquisa
55.78%
Previous studies showed that dietary l-arginine supplementation decreased white fat mass in genetically obese rats. This study tested the effectiveness of l-arginine in diet-induced obesity. Male Sprague-Dawley rats were fed for 15 wk a high-fat (HF) (40% energy) or low-fat (LF) (10% energy) diet beginning at 4 wk of age, resulting in 18% higher body weight gains and 74% higher weights of major white fat pads (retroperitoneal, epididymal, subcutaneous, and mesenteric adipose tissues) in HF than in LF fed rats. Starting at 19 wk of age, rats in each dietary group were supplemented for 12 wk with 1.51% l-arginine-HCl or 2.55% l-alanine (isonitrogenous control) (n = 8 per treatment) in drinking water and arginine groups were individually pair-fed to alanine controls. Despite similar energy intake, absolute weights of white fat pads increased by 98% in control rats over a 12-wk period but only by 35% in arginine-supplemented rats. The arginine treatment reduced the relative weights of white fat pads by 30% and enhanced those of soleus muscle by 13%, extensor digitorum longus muscle by 11%, and brown fat by 34% compared with control rats. Serum concentrations of insulin, adiponectin, growth hormone, corticosterone, triiodothyronine, and thyroxine did not differ between control and arginine-supplemented rats. However...

Effects of Supplementing Brown Seaweed By-products in the Diet of Holstein Cows during Transition on Ruminal Fermentation, Growth Performance and Endocrine Responses

Hong, Z. S.; Kim, E. J.; Jin, Y. C.; Lee, J. S.; Choi, Y. J.; Lee, H. G.
Fonte: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST) Publicador: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST)
Tipo: Artigo de Revista Científica
Publicado em /09/2015 EN
Relevância na Pesquisa
55.78%
This study was conducted to examine the effects of supplementing brown seaweed by-products (BSB) in the diet of ruminants on ruminal fermentation characteristics, growth performance, endocrine response, and milk production in Holstein cows. In Experiment 1, the effects of different levels (0%, 2%, and 4% of basal diet as Control, 2% BSB, 4% BSB, respectively) of BSB were evaluated at 3, 6, 9, 12, and 24 h in vitro batch culture rumen fermentation. The pH tended to be higher for the higher level of BSB supplementation, with the pH at 12 h being significantly higher (p<0.05) than that of the control. The concentration of ammonia nitrogen was lower at 3, 9, 12, and 24 h incubation (p<0.05) compared with the control, and tended to be low at other incubation times. Volatile fatty acid concentration appeared to be minimally changed while lower values were observed with 4% BSB treatment at 24 h (p<0.05). In Experiment 2, effects of levels (0%, 2%, and 4%) of BSB on growth performance, endocrine responses and milk production were studied with Holstein dairy cows during transition. Dry matter intake, daily gain and feed efficiency were not affected by BSB supplementation. The concentration of plasma estrogen for the control, 2% BSB and 4% BSB after three months of pregnancy were 55.7...

Influence of Rapeseed Meal on Growth Performance, Blood Profiles, Nutrient Digestibility and Economic Benefit of Growing-finishing Pigs

Choi, H. B.; Jeong, J. H.; Kim, D. H.; Lee, Y.; Kwon, H.; Kim, Y. Y.
Fonte: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST) Publicador: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST)
Tipo: Artigo de Revista Científica
Publicado em /09/2015 EN
Relevância na Pesquisa
55.78%
This study was conducted to investigate the influence of dietary rapeseed meal (RSM) on growth performance, blood profiles, nutrient digestibility and economic benefit of growing-finishing pigs. A total of 120 growing pigs ([Yorkshire×Landrace] ×Duroc) with an initial body weight (BW) 29.94±0.06 kg were used in this experiment. Pigs were randomly allotted into 1 of 5 treatments in a randomized complete block design and 6 replicates with 4 pigs per pen. Treatments were divided by dietary RSM supplementation levels (0%, 3%, 6%, 9%, or 12%) in growing-finishing diets. A linear decrease (p<0.05) of BW and average daily gain (ADG) were observed at 13th wk of finishing and overall periods of pigs. Additionally, gain-to-feed ratio (G/F) tended to decrease by dietary RSM supplementation in growing-finishing diets (linear, p = 0.07 and quadratic, p = 0.08). Concentrations of serum triiodothyronine and thyroxine were not influenced by dietary RSM treatments whereas thyroid gland and liver weight were increased at 13th wk of finishing period (linear, p<0.05; p<0.01) by increasing dietary RSM supplementation level. In blood profiles, serum total cholesterol and low density lipoprotein cholesterol concentrations were not differed by dietary treatments at 13th wk of finishing period whereas concentration of serum high density lipoprotein cholesterol was affected by the supplementation level of RSM...

Thyrotropin releasing hormone (TRH) and lung maturation: Does 200mcg TRH provide effective stimulation to the preterm pituitary gland compared with 400mcg?

Crowther, C.; Haslam, R.; Hiller, J.; McGee, T.; Ryall, R.; Robinson, J.
Fonte: C.V. Mosby Publicador: C.V. Mosby
Tipo: Artigo de Revista Científica
Publicado em //1995 EN
Relevância na Pesquisa
46.33%
OBJECTIVE: Our purpose was to compare the response of the fetal pituitary-thyroid axis to 200 and 400 micrograms of thyrotropin-releasing hormone administered to the mother immediately before delivery with a control group. STUDY DESIGN: A randomized controlled trial was conducted of 26 women at gestational ages between 24 weeks and 33 weeks 6 days who had received one or more doses of betamethasone who were expected to be delivered within 1 to 4 hours. Women received either 200 or 400 micrograms of thyrotropin-releasing hormone or were in the control group. RESULTS: Thyroid-stimulating hormone determinations on cord blood had a higher mean level in both treatment groups compared with the control group. No differences were seen in cord blood results between the two treatment groups for thyroid-stimulating hormone, thyroxine, triiodothyronine, free thyroxine, free triiodothyronine, and prolactin levels. The only other differences found were in a higher level in total thyroxine and a lower level of free thyroxine in the 400 micrograms thyrotropin-releasing hormone group compared with the 200 micrograms group in the 48-hour blood determinations. CONCLUSION: Both 200 and 400 micrograms of thyrotropin-releasing hormone provided fetal pituitary stimulation...

Effect of grazing pasture with a low selenium content on the concentrations of triiodothyronine and thyroxine in serum, and GSH-Px activity in erythrocytes in cows in Chile

Fonte: Universidade Católica de Temuco Publicador: Universidade Católica de Temuco
Tipo: Artículo de Revista
EN
Relevância na Pesquisa
56.08%
AIM: To determine the effect of grazing pasture that had a low selenium (Se) concentration on serum concentrations of triiodothyronine (T3) and thyroxine (T4), and erythrocyte glutathione peroxidase (GSH-Px) activity in dairy cows. METHODS: Forty pregnant Friesian cows were grazed on pasture that contained 0.03-0.04 ppm Se on a dry matter (DM) basis. Two months before parturition, 20 cows were randomly selected and treated with 1 mg Se/kg bodyweight subcutaneously, as barium selenate (Group Se-S). The other group (Se-D) was not supplemented. Blood samples were taken before supplementation (-60 days) and 30, 60, 90, 180 and 270 days after parturition, for determination of concentrations of T3 and T4 in serum, and GSH-Px activity in erythrocytes. RESULTS: Erythrocyte GSH-Px activity in the Se-D group was <60 U/g haemoglobin (Hb) throughout the experiment. Supplementation increased (p<0.05) activities to >130 U/g Hb throughout lactation. Mean serum concentrations of T4 in Se-D and Se-S cows increased from 23.7 (SEM 0.7) and 23.4 (SEM 0.8) nmol/L, respectively, in the prepartum period to 69.6 (SEM 0.1) and 67.6 (SEM 0.2) nmol/L, respectively, at 180 days of lactation (p<0.01), and no effect of Se supplementation was evident. Serum concentrations of T3 in Se-D cows decreased (p<0.05) from 1.6 (SEM 0.1) nmol/L prepartum to 1.0 (SEM 0.2) nmol/L at the beginning of lactation...

Alterations in 3,3'5'-triiodothyronine metabolism in response to propylthiouracil, dexamethasone, and thyroxine administration in man.

LoPresti, J S; Eigen, A; Kaptein, E; Anderson, K P; Spencer, C A; Nicoloff, J T
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1989 EN
Relevância na Pesquisa
46.17%
To elucidate the mechanisms involved in altering serum 3,3',5'-triiodothyronine (rT3) levels with absolute or relative low 3,5,3'-triiodothyronine (T3) states in man, agents capable of lowering circulating T3 levels were sequentially administered to six euthyroid subjects. These agents included propylthiouracil (PTU) (300 mg/6 h X 5 d), dexamethasone (DEX) (2 mg/6 h X 5 d), and thyroxine (T4) (3.0 mg load and 0.3 mg/d X 5 d). [125I] rT3 clearance rates and rT3 production rates were then determined. Increased serum rT3 levels and rT3/T4 values occurred with both PTU and DEX as compared with control, while T4 increased serum rT3 but did so without changing rT3/T4 values. The rT3 clearance rate was significantly decreased by PTU without altering production rate, while DEX increased the rT3 production rate without altering the rT3 clearance rate. T4 administration did not change rT3 clearance but proportionately increased rT3 production. These responses indicate that circulating rT3 predominantly originates from a non-PTU inhibitable deiodinase enzyme system located in extrahepatic tissues. This enzyme system appears to have a high capacity and low affinity for T4 and can be stimulated by DEX administration.

Synthesis of thyroid hormone metabolites by photolysis of thyroxine and thyroxine analogs in the near UV.

van der Walt, B; Cahnmann, H J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1982 EN
Relevância na Pesquisa
46.38%
Photolysis of thyroxine and its analogs in the near UV permitted synthesis in good yield of picogram to gram quantities of thyroid hormone metabolites. Preparation of the same metabolites by classical chemical synthesis requires multistep procedures. Specifically labeled metabolites of high specific activity (e.g., those carrying the label in the nonphenolic ring) were obtained by photolysis of appropriately labeled thyroxine or 3',3',5'-triiodothyronine (reverse triiodothyronine). Some of these labeled metabolites, which are required for metabolic studies (3-iodothyronine and 3,3'-diiodothyronine, labeled in the nonphenolic ring), had not previously been obtained by other methods. Irradiation of thyroxine and reverse triiodothyronine in 150 mM methanolic ammonium hydroxide with greater than 340-nm light caused removal of one iodine atom from the phenolic ring with formation of 3,5,3'-triiodothyronine and 3,3'-diiodothyronine, respectively. Irradiation with higher-energy light (greater than 300 nm) led to stepwise removal of additional iodine atoms. Those in the phenolic ring were removed preferentially, so that 3,5-diiodothyronine and 3-iodothyronine, respectively, were formed. The iodine atoms in the nonphenolic ring were lost more slowly. Tetraiodothyroacetic acid followed a similar photodeiodination pattern. Photolysis with light in the near UV is a simple method for the synthesis of thyroid hormone metabolites.

Neonatal thyroid function: prematurity, prenatal steroids, and respiratory distress syndrome.

Franklin, R C; Purdie, G L; O'Grady, C M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1986 EN
Relevância na Pesquisa
46.43%
Indices of thyroid function were measured in 97 preterm infants at birth and at 5, 10, and 15 days of age. Triiodothyronine uptake, free thyroxine index, thyroxine, free thyroxine, triiodothyronine, reverse triiodothyronine, and thyroxine binding globulin values at birth correlated with gestational age, whereas thyroid stimulating hormone values did not. Treatment with steroids prenatally had no apparent effect on thyroid function at birth or postnatally. Infants developing respiratory distress syndrome had normal values for all indices at birth. These infants had significantly lower thyroxine, free thyroxine index, free thyroxine, and triiodothyronine values at 5 days of age, while thyroid stimulating hormone values remained normal. This alteration in thyroid function was interpreted as being secondary to respiratory distress syndrome. Gestational maturity and respiratory distress syndrome, if present, must be taken into account when evaluating thyroxine variables in preterm infants, whereas measurement of thyroid stimulating hormone as the screen for congenital hypothyroidism circumvents these considerations.

Controlled Clinical Trial of Combined Triiodothyronine and Thyroxine in the Treatment of Hypothyroidism

Smith, R. N.; Taylor, S. A.; Massey, J. C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 17/10/1970 EN
Relevância na Pesquisa
76.24%
A -double-blind crossover trial of a combined preparation of triiodothyronine and thyroxine (1:4 ratio) compared with thyroxine alone was conducted with 99 patients previously stabilized on. thyroxine as treatment for hypothyroidism. Four patients were excluded during the trial and eight afterwards owing to gross deficiencies in taking the tablets. Of the remaining 87 patients 42 (48%) had no -preference for either medication, 29 (33%) preferred thyroxine alone, and 16 (18%) the combination. A high incidence of unpleasant symptoms was experienced during the two months' treatment with the combined preparation. The serum protein-bound iodine levels were lowered (mean reduction 1·8 μg./100 ml.) on the combination, but the labelled T3-resin sponge uptake values were not altered and remained in the normal range. on both treatments.