Association between sensitivity to thyroid hormones and non-highdensity lipoprotein cholesterol levels in patients with type 2 diabetes mellitus

BACKGROUND Dyslipidemia and type 2 diabetes mellitus(T2DM)are chronic conditions with substantial public health implications.Effective management of lipid metabolism in patients with T2DM is critical.However,there has been insufficient attention given to the relationship between thyroid hormone sensitivity and dyslipidemia in the T2DM population,particularly concerning non-high-density lipoprotein cholesterol(non-HDL-C).AIM To clarify the association between thyroid hormone sensitivity and dyslipidemia in patients with T2DM.METHODS In this cross-sectional study,thyroid hormone sensitivity indices,the thyroid feedback quantile-based index(TFQI),the thyroid-stimulating hormone index(TSHI),the thyrotrophic T4 resistance index(TT4RI),and the free triiodothyronine(FT3)/free thyroxine(FT4)ratio were calculated.Logistic regression analysis was performed to determine the associations between those composite indices and non-HDL-C levels.Random forest variable importance and Shapley Additive Explanations(SHAP)summary plots were used to identify the strength and direction of the association between hyper-non-HDL-C and its major predictor.RESULTS Among the 994 participants,389(39.13%)had high non-HDL-C levels.Logistic regression analysis revealed that the risk of hyper-non-HDL-C was positively correlated with the TFQI(OR:1.584;95%CI:1.088-2.304;P=0.016),TSHI(OR:1.238;95%CI:1.034-1.482;P=0.02),and TT4RI(OR:1.075;95%CI:1.006-1.149;P=0.032)but was not significantly correlated with the FT3/FT4 ratio.The relationships between composite indices of the thyroid system and non-HDL-C levels differed according to sex.An increased risk of hyper-non-HDL-C was associated with elevated TSHI levels in men(OR:1.331;95%CI:1.003-1.766;P=0.048)but elevated TFQI levels in women(OR:2.337;95%CI:1.4-3.901;P=0.001).Among the analyzed variables,the average SHAP values were highest for TSHI,followed by TT4RI.CONCLUSION Impaired sensitivity to thyroid hormones was associated with high non-HDL-C levels in patients with T2DM.

Association of Serum Ferritin Levels and Thyroid Hormones

Thyroid metabolism is orchestrated by the action of various minerals and trace elements including iron, iodine, selenium, and zinc. Iron deficiency, specifically deficiency in serum ferritin levels, is one of the common causes of thyroid dysfunction. Our objective was to evaluate the relationship between serum ferritin levels and circulating thyroid hormones. For this, a retrospective analysis was performed on 16,512 individuals who tested for serum levels of ferritin and thyroid profile at Vibrant America Clinical Laboratories. Subjects were stratified based on the serum levels of ferritin. Age (p −0.03232, p < 0.0001). Analysis of Linear association by Pearson’s correlation exhibited a considerable correlation between varying serum ferritin levels with all tested thyroid hormones. The study concludes that serum ferritin levels were associated with thyroid hormone synthesis and metabolism in individuals with optimal levels of circulating ferritin.

Thyroid hormones and thyroid hormone receptors: Effects of thyromimetics on reverse cholesterol transport

Reverse cholesterol transport (RCT) is a complex process which transfers cholesterol from peripheral cells to the liver for subsequent elimination from the body via feces. Thyroid hormones (THs) affect growth, develop- ment, and metabolism in almost all tissues. THs exert their actions by binding to thyroid hormone receptors (TRs). There are two major subtypes of TRs, TRα and TRβ, and several isoforms (e.g. TRα1, TRα2, TRβ1, and TRβ2). Activation of TRα1 affects heart rate, whereas activation of TRβ1 has positive effects on lipid and lipoprotein metabolism. Consequently, particular interest has been focused on the development of thyromimetic compounds targeting TRβ1, not only because of their ability to lower plasma cholesterol but also due their ability to stimulate RCT, at least in pre-clinical models. In this review we focus on THs, TRs, and on the effects of TRβ1-modulating thyromimetics on RCT in various animal models and in humans.

Stimulating effect of thyroid hormones in peripheral nerve regeneration:research history and future direction toward clinical therapy

Injury to peripheral nerves is often observed in the clinic and severe injuries may cause loss of motor and sensory functions.Despite extensive investigation,testing various surgical repair techniques and neurotrophic molecules,at present,a satisfactory method to ensuring successful recovery does not exist.For successful molecular therapy in nerve regeneration,it is essential to improve the intrinsic ability of neurons to survive and to increase the speed of axonal outgrowth.Also to induce Schwann cell phenotypical changes to prepare the local environment favorable for axonal regeneration and myelination.Therefore,any molecule that regulates gene expression of both neurons and Schwann cells could play a crucial role in peripheral nerve regeneration.Clinical and experimental studies have reported that thyroid hormones are essential for the normal development and function of the nervous system,so they could be candidates for nervous system regeneration.This review provides an overview of studies devoted to testing the effect of thyroid hormones on peripheral nerve regeneration.Also it emphasizes the importance of combining biodegradable tubes with local administration of triiodothyronine for future clinical therapy of human severe injured nerves.We highlight that the local and single administration of triiodothyronine within biodegradable nerve guide improves significantly the regeneration of severed peripheral nerves,and accelerates functional recovering.This technique provides a serious step towards future clinical application of triiodothyronine in human severe injured nerves.The possible regulatory mechanism by which triiodothyronine stimulates peripheral nerve regeneration is a rapid action on both axotomized neurons and Schwann cells.

Amphibian metamorphosis as a model for studying the developmental actions of thyroid hormone

The thyroid hormones L-thyroxine and triiodo-L-thyronine have profound effects on postembryonic development of most vertebrates. Analysis of their action in mammals is vitiated by the exposure of the developing foetus to a number of maternal factors which do not allow one to specifically define the role of thyroid hormone (TH)or that of other hormones and factors that modulate its action. Amphibian metamorphosis is obligatorily dependent on TH which can initiate all the diverse physiological manifestations of this postembryonic developmental process(morphogenesis, cell death, re-structuring, etc.) in free-living embryos and larvae of most anurans. This article will first describe the salient features of metamorphosis and its control by TH and other hormones. Emphasis will be laid on the key role played by TH receptor (TR), in particular the phenomenon of TR gene autoinduction, in initiating the developmental action of TH. Finally, it will be argued that the findings on the control of amphibian metamorphosis enhance our understanding of the regulation of postembryonic development by TH in other vertebrate species.

Thyroid hormone regulation of apoptotic tissue remodeling during anuran metamorphosis

Anuran metamorphosis involves systematic transformations of individual organs in a thyroid hormone (TH)-dependent manner. Morphological and cellular studies have shown that the removal of larval or- gans/tissues such the tail and the tadpole intestinal epithelium is through programmed cell death or apop- tosis. Recent molecular investigations suggest that TH regulates metamorphosis by regulating target gene expression through thyroid hormone receptors (TRs), which are DNA-binding transcription factors. Cloning and characterization of TH response genes show that diverse groups of early response genes are induced by TH. The products of these TH response genes are believed to directly or indirectly affect the expression and/or functions of cell death genes, which are conserved at both sequence and function levels in different animal species. A major challenge for future research lies at determining the signaling pathways leading to the activation of apoptotic processes and whether different death genes are involved in the regulation of apoptosis in different tissues/organs to effect tissue-specific transformations.

Inhibition effects of parathyroid hormone on human medullary thyroid carcinoma cells

Objective： The purpose of the study was to investigate the effects of parathyroid hormone and parathyroid hormone receptor monoclonal antibody on in vitro growth and proliferation of human medullary thyroid carcinoma cell lines. Methods： The medullary thyroid carcinoma cell line was cultured in vitro, with parathyroid hormone and parathyroid hormone receptor monoclonal antibody treatment intervention, the growth of the cells was observed under an inverted contrast micro scope, the MTT assay was used to detect the cell growth inhibition rate. Results： Under the inverted contrast microscope, the cells changed significantly, the parathyroid hormone and parathyroid hormone receptor monoclonal antibodies can effectively inhibit the proliferation of medullary thyroid cancer cells in a time and dose dependent. When parathyroid hormone concentra tion reached a concentration of 2.0 IJmol/L, the parathyroid hormone receptor monoclonal antibody reached a concentration of 1.0 μmol/L, the cell growth was most significantly inhibited （P 〈 0.05）. Conclusion： Parathyroid hormone and parathyroid hormone receptor monoclonal antibody were able to inhibit the proliferation of medullary thyroid carcinoma cells and signifi cantly reduce the proliferation index.

Role and Mechanisms of Actions of Thyroid Hormone on the Skeletal Development

The importance of the thyroid hormone axis in the regulation of skeletal growth and maintenance has been well established from clinical studies involving patients with mutations in proteins that regulate synthesis and/or actions of thyroid hormone. Data from genetic mouse models involving disruption and overexpression of components of the thyroid hormone axis also provide direct support for a key role for thyroid hormone in the regulation of bone metabolism. Thyroid hormone regulates proliferation and/or differentiated actions of multiple cell types in bone including chondrocytes, osteoblasts and osteoclasts. Thyroid hormone effects on the target cells are mediated via ligand-inducible nuclear receptors/transcription factors, thyroid hormone receptor （TR） a and ~, of which TRa seems to be critically important in regulating bone cell functions. In terms of mechanisms for thyroid hormone action, studies suggest that thyroid hormone regulates a number of key growth factor signaling pathways including insulin-like growth factor-I, parathyroid hormone related protein, fibroblast growth factor, Indian hedgehog and Wnt to influence skeletal growth. In this review we describe findings from various genetic mouse models and clinical mutations of thyroid hormone signaling related mutations in humans that pertain to the role and mechanism of action of thyroid hormone in the regulation of skeletal growth and maintenance.

Toxic Effects of Tetrabromobisphenol A on Thyroid Hormones in SD Rats and the Derived-reference Dose

The present study determined the thyroid hormone interference of tetrabromobisphenol A （TBBPA） in Sprague-Dawley （SD） rats, and the derived-reference dose （RfD） of different endpoint effects on mammals based on experimental results and data collection. Based on repeated exposure toxicity tests on mammals and extensive research, the present study used BMDS240 Software to derive a benchmark dose, and analyzed the accuracy and uncertainty, and similarity with other studies. Test results on triiodothyronine （T3）, thyroxine （T4）, and thyroid stimulating hormone （TSH） demonstrated that all the indicators presented a non-monotonous dose-effect relationship clearly, except TSH in male rats exposed to 0-1000 mg/kg BW per day. Therefore, RfDs were derived from different critical effects. In summary, RfD for mammals in the present study was found to be 0.6 mg/kg per day.

Iodothyronine deiodinase gene analysis of the Pacific oyster Crassostrea gigas reveals possible conservation of thyroid hormone feedback regulation mechanism in mollusks

Iodothyronine deiodinase catalyzes the initiation and termination of thyroid hormones(THs) effects, and plays a central role in the regulation of thyroid hormone level in vertebrates. In non-chordate invertebrates, only one deiodinase has been identified in the scallop C hlamys farreri. Here, two deiodinases were cloned in the Pacific oyster C rassostrea gigas( Cg Dx and C g Dy). The characteristic in-frame TGA codons and selenocysteine insertion sequence elements in the oyster deiodinase c DNAs supported the activity of them. Furthermore, seven orthologs of deiodinases were found by a tblastn search in the mollusk Lottia gigantea and the annelid C apitella teleta. A phylogenetic analysis revealed that the deiodinase gene originated from an common ancestor and a clade-specific gene duplication occurred independently during the differentiation of the mollusk, annelid, and vertebrate lineages. The distinct spatiotemporal expression patterns implied functional divergence of the two deiodinases. The expression of C g Dx and Cg Dy was influenced by L-thyroxine T4, and putative thyroid hormone responsive elements were found in their promoters, which suggested that the oyster deiodinases were feedback regulated by TH. Epinephrine stimulated the expression level of C g Dx and Cg Dy, suggesting an interaction effect between different hormones. This study provides the first evidence for the existence of a conserved TH feedback regulation mechanism in mollusks, providing insights into TH evolution.

Changes of serum thyroid hormone and plasma catecholamine of 16 th and 17 th Chinese Expeditioners in Antarctic environment

The serum thyroid hormone and plasma catecholamine were examined in 18 male and 2 female members of the Chinese Antarctic Expedition (who spent the 2000 or 2001 austral winter at the Great Wall Station) . The changes of serum thyroid hormone i. e. total thyroxine (TT4) and free T4 (FT4) , total triodothyronine (TT3) and freeT3 ( FT3 ) , thyroid stimulating hormone ( TSH ) and plasma catecholamine, including norepinephrine (NE) , epinephrine ( E) and dopamine ( DA ) , were investigated by Chemoluminescence Immunoassay (CLIA) and High Performance Liquid Chromatography with electrochemical detection (HPLC-ECD) . Samples were taken at different time; (1)1 day before departure to Antarctica (16th expedition 1999/12/ 09; 17th expedition 2000/12/06). (2) 1 day after returned to China after living 54 weeks in Antarctica ( 16th expedition 2000/12/25 ; 17th expedition 2001/12/25 ). Comparing the data of before departure and returned, results showed that there was a significant decrease in the contents of TT4 (P <0. 01) with no significant change in the content of TT3 , FT3 and FT4. It was also found that the content of TSH increased significantly (P <0. 001) ; No significant changes of plasma NE and DA were found but the content of E decreased significantly ( P < 0. 001) . The results indicated that the special Antarctic environment led to a restrain effect on the thyroid function and the level of plasma E in Antarctic expedition members. Both the thyroid and adrenal medulla system were associated in response to the Antarctic systemic stress.

Prevalence of hypothyroidism and effect of thyroid hormone replacement therapy in patients with non-alcoholic fatty liver disease:A population-based study

BACKGROUND Non-alcoholic fatty liver disease(NAFLD)is currently considered as the most common cause of chronic liver disease worldwide.Risk factors for NAFLD have been well-described,including obesity,type 2 diabetes mellites(T2DM),dyslipidemia(DLP)and metabolic syndrome.Hypothyroidism has been identified as an independent risk factor for the development of NAFLD,although the literature is inconsistent AIM To evaluate the prevalence of hypothyroidism in patients with NAFLD,assess if it is an independent risk factor and explore the effect of thyroxine replacement therapy.METHODS Our cohort’s data was obtained using a validated,large,multicenter database(Explorys Inc,Cleveland,OH,United States)aggregated from pooled outpatient and inpatient records of 26 different healthcare systems,consisting of a total of 360 hospitals in the United States,and utilizing Systematized Nomenclature of Medicine-Clinical Terms for coding.We evaluated a cohort of patients with hypothyroidism and NAFLD.Multivariate analysis was performed to adjust for confounding risk factors including hypertension(HTN),T2DM,DLP,obesity and metabolic syndrome.SPSS version 25,IBM Corp was used for statistical analysis,and for all analyses,a 2-sided P value of<0.05 was considered statistically significant.Exclusion criteria were limited to age<18 years.RESULTS Among the 37648180 included individuals in this database who are above the age of 18 years,there were a total of 2320 patients with NAFLD(6.16 per 100000)in the last five years(2015-2020),amongst which 520 patients(22.4%)had hypothyroidism.Baseline characteristics of patients in this database are described in Table 1.Patients with NAFLD were also more likely to have obesity,T2DM,DLP,HTN,and metabolic syndrome(Table 2).While males and females were equally affected,patients in the age group 18-65 years as well as Caucasians seem to be at a higher risk.There was an increased risk of NAFLD among patients with hypothyroidism(OR=1.587).Furthermore,thyroid hormone replacement was not associated with a decreased risk for developing NAFLD(OR=1.106,C=0.952-1.285,P=0.303).CONCLUSION Hypothyroidism seems to be an independent risk factor for the development of NAFLD.Thyroid hormone replacement did not provide a statistically significant risk reduction.Further studies are needed to evaluate the effect of thyroid hormone replacement and assess if being euthyroid while on thyroid replacement therapy affects development and/or progression of NAFLD.

Involvement of chromatin and histone acetylation in the regulation of HIV-LTR by thyroid hormone receptor

The HIV-1 LTR controls the expression of HIV-1 viral genes and thus is critical for viral propagation and pathology. Numerous host factors have been shown to participate in the regulation of the LTR promoter. Among them is the thyroid hormone (T3) receptor (TR). TR has been shown to bind to the critical region of the promoter that contain the NFbB and Sp1 binding sites. Interestingly, earlier transient transfection studies in tissue culture cells have yielded contradicting conclusions on the role of TR in LTR regulation, likely due to the use of different cell types and/or lack of proper chromatin organization. Here, using the frog oocyte as a model system that allows replication-coupled chromatin assembly, mimicking that in somatic cells, we demonstrate that unliganded heterodimers of TR and RXR (9-cis retinoic acid receptor) repress LTR while the addition of T3 relieves the repression and further activates the promoter. More importantly, we show that chromatin and unliganded TR/RXR synergize to repress the promoter in a histone deacetylase-dependent manner.

Effects of topiramate and carbamazepine on thyroid hormone level in adults with epilepsy

BACKGROUND: It has been demonstrated that traditional antiepileptics, such as phenytoin, carbamazepine (CBZ), phenobarbital, etc., can result in the decrease of thyroid hormone of epileptic patients. However, there is still no sufficient evidence for the studies about the effect of new-type antiepileptics, such as topiramate (TPM), on thyroid hormones. OBJECTIVE: To observe the effects of TPM and CBZ on the level of thyroid hormones in serum of adults with epilepsy. DESIGN: A comparative observation. SETTING: Department of Neurology, Sichuan Provincial People's Hospital. PARTICIPANTS: Totally 100 outpatients or inpatients newly diagnosed to have epilepsy were selected from the Department of Neurology, Sichuan Provincial People's Hospital from July 2003 to August 2005, including 60 males and 40 females, aged 18-70 years. All the patients were accorded with the standard for the classification of epilepsy set by International League Against Epilepsy (ILAE) in 1981; Had been Informed and agreed with the detection; Had no history of thyroid gland disease; Had not taken any drugs could affect the thyroid function. Meanwhile, 40 adult healthy examinees were selected from our hospital as the control group, including 24 males and 16 females, aged 18-65 years. METHODS: ① The 100 epileptic patients were randomly divided into TPM group (n =50) and CBZ group (n =50), and they were treated with TPM (Xian-Janssen Pharmaceutical, Ltd.; Batch number: 03AS032, Norm: 25 mg/tablet) and CBZ (Shanghai Sunve Pharmaceutical Co., Ltd.; Batch number: 030201, Norm: 100 mg/tablet) respectively. The initial dosage of TPM was 25 mg per day, increased by 25 mg every week, the objective dosage of 100-200 mg per day was maintained when the symptoms were satisfactorily controlled. The dosage of CBZ was 6-8 mg/kg per day. All the patients were administrated for 1 year. ② The serum levels of total thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3), free triiodothyronine (FT3) and thyroid stimulating hormone (TSH) in the epileptic patients were detected by means of chemiluminescence before treatment and at 3, 6 and 12 months after treatment respectively. ③Standards for judging curative effects: Controlled by without seizure, the frequency of seizure reduced by ≥ 75% was taken as significant effect, reduced by 50%-74% as effect, and reduced by < 49% as invalid, whereas increased by more than 20% was taken as aggravation. ④ The intergroup and intragroup differences of the measurement data were compared by the analysis of variance and paired t test respectively. MAIN OUTCOME MEASURES: Serum levels of thyroid hormones before treatment and at different time points after treatment of TPM and CBZ. RESULTS: All the 100 epileptic patients and 40 healthy subjects were involved in the analysis of results. ① Changes of serum levels of thyroid hormones: The serum levels of TT3, TT4, FT3, FT4 and TSH were close between the epileptic patients and normal subjects before treatment (P > 0.05). In the CBZ group, the serum levels of FT4 at 3, 6 and 12 months after treatment [(16.87±3.77), (16.34±3.98) , (16.97±3.95) pmol/L] were significantly decreased as compared with those before treatment [(18.00±3.54) pmol/L, t =2.74, 3.50, 2.26, P < 0.05]; The levels of TT3 at 3, 6 and 12 months [(2.09±0.54), (1.99±0.49), (1.84±0.47) nmol/L] were significantly decreased as compared with those before treatment [(2.22±0.63) nmol/L, t =2.73, 2.78, 5.18, P < 0.05]. The levels of TT3 at 6 and 12 months [(109.65±23.98), (107.72±23.90) nmol/L] were significantly decreased as compared with those before treatment [(118.98±28.48) nmol/L, t =3.11, 3.30, P < 0.05]. TT4 level in serum at 3 months and the levels of FT3 and TSH at each time point after CBZ treatment had no obvious changes as compared with those before treatment (P > 0.05). In the TPM group, the levels of thyroid hormones at each time point had no obvious changes as compared with those before treatment (P > 0.05). ② Curative effects: Of the 100 epileptic patients, it was controlled in 12 cases, significantly effective in 30 cases, effective in 39 cases and invalid in 19 cases, the total effective rate was 81% (81/100). CONCLUSION: CBZ treatment can lead to the decreases of thyroid hormones in adult epileptic patients. Epilepsy itself and TPM treatment cannot change the thyroid hormones in adult epileptic patients, which suggests that TPM treatment is safer for the thyroid function of adult epileptic patients.

Thyroid hormone levels during early periods of ischemic and hemorrhagic stroke could serve as an indicator of prognosis

BACKGROUND： Predicting the outcome of stroke during the acute phase is difficult. Accurate methods for predicting outcomes could assist clinicians and families to make correct decisions in resource-poor environments. OBJECTIVE： To determine thyroid hormone levels in patients with ischemic or hemorrhagic stroke at the early stage, and to investigate its correlation with stroke prognosis. DESIGN, TIME AND SETTING： A comparative, observational study was performed at the Department of Emergency, Tertiary-care University Affiliated Hospital from January 2004 to January 2006. PARTICIPANTS： A total of 113 patients presenting to the Emergency Department within 3 hours of stroke symptom onset were approached for enrollment in the study. The patients were diagnosed by computer tomography examination, and comprised 87 ischemic stroke and 26 hemorrhagic stroke patients. METHODS： Following a thorough history and examination by emergency physicians, venous blood samples were collected from each patient. Thyroid-stimulating hormone （TSH）, free triiodothyronine （free T3）, and free thyroxine （free T4） levels were measured using a chemiluminescence method. The nerve function of patients was evaluated with Glasgow Coma Scale （GCS） score, and the patients were accordingly assigned to two subgroups-mild stroke （GCS ≥ 9） and severe stroke （GCS ≤ 8）. MAIN OUTCOME MEASURES： Blood levels of TSH, free T3 and free T4; mortality at 7 days. RESULTS： Mean TSH values in hemorrhagic stroke patients with GCS ≤ 8 were significantly greater than those in ischemic stroke patients with GCS ≤ 8 and GCS ≥ 9 （P 〈 0.05）. Compared with patients who survived, the highest TSH levels were detected in patients that had died within 7 days. Correlation analysis results revealed a significant negative relationship between GCS values and TSH levels in patients with hemorrhagic stroke （r= 0.552, P〈 0.01）, and no correlation was determined between GCS values and TSH levels in patients with ischemic stroke （r = 0.239, P 〉 0.05）. CONCLUSION： In patients with hemorrhagic stroke, high TSH levels were observed within the first 3 hours of stroke onset, which could be considered an indicator of poor prognosis.

Regulations of Thyroid Hormone on Cardiac Protein Kinase C Signal Pathway in vitro

The experiments were conducted to assess the influences of thyroid hormone on cardiac protein kinase C(PKC) signal pathway with cultured cardiac myocytes and fibroblasts as the models. Cells were pretreated with 1% newborn calf serum (NCS) or angiotensin II (Ang II), and then following by a triiodothyronine (T3) treatment. The PKC activity, PKCα and PKCε expressions were analyzed and compared. In 1% NCS pretreatment, T3 could inhibit PKC activity and PKCε expression in cardiac myocytes. The AngII pretreatment led to an increase of PKC activity and PKCε expression in cardiac myocytes, and an increase of PKC activity in cardiac fibroblasts. Following by T3 treatment, the increased PKC activity and PKCε expression in cardiac myocytes were markedly decreased. In conclusion, whether in 1% NCS or in Ang II pretreatment, T3 could inhibit PKC activity and PKCε expression in cardiac myocytes. Key words thyroid hormone - cardiac myocytes - cardiac fibroblasts - protein kinase C CLC number Q 572 Foundation item: Supported by the Natural Science Foundation of Hubei Province (98091)Biography: WANG Bao-hua (1974-), female, Ph. D, research direction: cardiovascular pathophysiology.

Molecular Characterization of Thyroid Hormone Receptors (TRs) and their Responsiveness to T3 in Microhylafissipes

To explore and enrich the molecular mechanisms of thyroid hormone receptors （TRs） in the metamorphosis of amphibians, the cDNA sequences of TRa and TRβ in Microhyla fissipes were cloned and characterized. TRa was 1 706 bp in length with an open reading frame （ORF） of 1 257 bp encoding a predicted protein of 418 amino acids and TRβ was 1 422 bp with an ORF of 1 122 bp encoding a predicted protein of 373 amino acids. Their protein sequences contained 4 conserved domains of the nuclear receptor superfamily with two highly conserved cysteine-rich zinc fingers in the DNA-binding domain, whereas TRβ was 42 amino acids shorter in its A/B domain than TRot. Highly-conserved sequences and structures indicated their conserved functions during metamorphosis. TRa expression reached peak at 12 h and then decreased from 12 h to 48 h. While dramatically up-regulated TRβ was observed after exposure of T3 within 24 h, and it was down-regulated from 24 h to 48 h. The expression pattern of TRβ is similar to that in the natural metamorphosis. Furthermore, tadpoles treated 24 h also resembled the climax of metamorphosis tadpoles and TRβ expression had higher responsiveness than TRa to T3 in M. fissipes. These results suggest M. fissipes may serve as the model to assay environmental compounds on TH signaling disruption.

Changes of Thyroid Hormone Levels in Epileptic Patients

We measured serum T3, T4, FT3, FT4 and thyrotropin (TSH) by radioimmunoassay in 150 patients with epilepsy. Of the 150 epileptic patients, 120 cases received single antiepileptic drug, including Sod valproate (VPA), carbamazepine (CBZ), phenytoin (PHT), or MixtBrodsky (MB). Each subgroup consisted of 30 cases. The other 30 were untreated epileptics. The results suggested that there was no significant difference in serum thyroid hormone levels among healthy control group, untreated group , and hepatic non-enzyme-inducing anticonvulsant group (P<0. 05). As compared with the three groups mentioned above, the serum T3, T4, FT3, FT4 concentrations of the enzyme inducer groups were decreased, however, significant decrease was found in PHT group and CBZ group (P<0. 05, P<0.005). All 12 patients with circulating thyroid hormone concentrations below normal reference values were given enzyme inducer. None of them revealed any clinical manifestation of hypothyroidism. There was no significant difference in serum TSH level among the above 6 groups (P<0. 05), and the serum TSH level of all patients was within normal reference limits. Our study showed that the changes of thyroid hormone in epileptics were due to the effect of some AEDs and not the disease itself. The disparity between the effect of enzyme inducer and that of non-enzyme-inducing anticonvulsants indicated that the hepatic microsomal enzyme system metabolizing thyroid hormone to be induced was the main mechanism for decreased serum thyroid hormone concentrations. Though the serum thyroid hormone levels of the enzyme inducer groups were decreased, no significant increase of the mean serum TSH concentration was found. This implies that AEDs may interfere the HPA function in some way.

Comparison of Thyroid Hormones Levels in Female Ducks Blood and Embryo

[Objeclive] The comparison of levels of thyroid hormones （T3, T4 and FT3） in female ducks serum and embryo of different embryonic age between Gaoyou duck and Jinding duck were made to provide basic data for further research. [Method] The levels of thyroid hormones （T3, T4 and FT3） in female ducks serum, fertilized eggs, and 7, 11,15, 19, 22, 28-days embryo of Gaoyou duck and Jinding duck were analyzed with radioimmunoassay （RIA）. [ Result]The levels of thyroid hormones in fertilized eggs were higher than those in serum of female ducks; different em- bryonic age hormone level of Gaoyou duck and Jinding duck in serum had almost the same variation trend, which was low but relatively stable after 15 days. [Condusion] The result suggested that thyroid hormones play an important role in duck embryonic development, especially in the early peded.

The adenoviral E1A protein relieves gene repression by receptors in v/vo displaces corepressors and unliganded thyroid hormone

The human adenovirus type 5 early region 1A （E1A） is one of two oncogenes present in the adenovirus genome and functions by interfering with the activities of cellular regulatory proteins. The E1A gene is alternatively spliced to yield five products. Earlier studies have revealed that E1A can regulate the function of thyroid hormone （T3） receptors （TRs）. However, analysis in yeast compared with transfection studies in mammalian cell cultures yields surprisingly different effects. Here, we have examined the effect of E1A on TR function by using the frog oocyte in vivo system, where the effects of E1A can be studied in the context of chromatin. We demonstrate that different isoforms of E1A have distinct effects on TR function. The two longest forms inhibit both the repression by unliganded TR and activation by T3-bound TR. We further show that E1A binds to unliganded TR to displace the endogenous corepressor nuclear receptor corepressor, thus relieving the repression by unliganded TR. On the other hand, in the presence of T3, E1A inhibits gene activation by T3-bound TR indirectly, through a mechanism that requires its binding domain for the general coactivator p300. Taken together, our results thus indicate that E1A affects TR function through distinct mechanisms that are dependent upon the presence or absence of T3.