Thyroxine Binding Research Articles

P1554AEFFECT OF HAEMODILUTION ON THYROID FUNCTION BEFORE AND AFTER HAEMODIALYSIS IN PATIENT WITH END-STAGE RENAL DISEASE

Abstract Background and Aims To study the factors involved in the low thyroid hormones in end - stage renal disease (ESRD), we compared thyroid function before and after hemodialysis (HD). Method The serum free thyroxine (fT4), free triiodothyronine (fT3), and thyroid - simulating hormone (TSH), thyroxine binding globulin (TBG) and thyroglobulin (Tg) levels were measured before and after HD in 12 patients with chronic glomerulonephritis (CGN, age; 48.7 ± 11.8 [mean ± SD]) and 11 patients with diabetic nephropathy (DN, age; 57.6 ± 6.5), comparing with controls (n = 13, age; 40.9 ± 11.3). Results The serum fT4, fT3 and TBG levels were low before HD but increased almost in parallel with the increase in hematocrit and albumin levels after HD in both ESRD groups. The serum TSH level was high before HD but decreased after HD and Tg level remained almost unchanged. In DN, serum fT4 levels was almost the same, but fT3 levels was lower with slightly higher TSH level, compared with CGN. Conclusion Significantly lower fT4, fT3 and TBG levels in ESRD before HD seemed to be due to hemodilution and almost corrected after HD. The TSH level was promptly normalized with elevated fT4, and Tg levels remained unchanged probably due to the balance between corrected hemodilution and rapid response to decreased TSH stimulation. It may better to evaluate thyroid function after HD in ESRD. Accelerated senile changes were suggested in DN.

SAT-LB45 Chronic Opioid Use as a Cause of Severe Hypothyroidism: A Case Report

Background: Hypogonadism and hypocortisolism are present in a sizeable proportion of chronic opioid users. (1) An association with hypothyroidism, however, has not been demonstrated. Clinical Case: A 56-year old woman with chronic pain syndrome on opioids presented from a nursing home with decreased level of consciousness and was found to be hypotensive requiring ICU admission. Several weeks prior to her presentation, she was hospitalized for progressive weakness and was found to have evidence of panhypopituitarism: low TSH (0.209 uIU/mL, nl 0.400 – 4.200), low free T4 (0.76 ng/dL, nl 0.80 – 1.50), low LH (<0.12 mIU/mL, nl 10.9 – 58.6), low FSH (1.7 mIU/mL, nl 16.7 – 113.6), and abnormal ACTH stim test (ACTH 6.4 pg/mL, nl 7.2 – 63; cortisol 0-min 3.8 mcg/dL, nl 6.7 – 22.6; 60-min 13.10). She was discharged on levothyroxine 25 mcg daily and prednisone 7.5 mg daily. On admission, her exam was notable for symmetric, non-pitting edema of the lower extremities to the knees with peau d’orange appearance. Initial tests revealed profound hypothyroidism with low TSH (0.381 uIU/mL), low free T4 (0.60 ng/dL), undetectable total T4 (<0.9 mcg/dL, nl 5 – 12.2), and undetectable free T3 (<1.00 pg/mL, nl 2.5 – 3.9). Thyroglobulin and TPO antibodies were within normal limits. Thyroxine binding globulin was low (6 mcg/mL, nl 13 -39). Additional biochemical studies re-demonstrated panhypopituitarism with low LH (<0.12 mIU/mL) and FSH (0.9 mIU/mL). Cortisol was elevated (73.2 mcg/dL) as she had received hydrocortisone. Despite fluid resuscitation and use of vasopressors, her hypotension persisted and she remained in critical condition. She was treated as a case of myxedema coma and started on full replacement dose thyroid hormone with 120 mcg IV levothyroxine daily and liothyronine 5 mcg every 8 hours. Over the next several days, the patient’s hemodynamics and mental status improved dramatically. A contrast-enhanced pituitary-protocoled MRI was notable for a moderately flattened sella (pituitary 3.5 mm in height) and absence of usual T1 bright signal in the posterior lobe. A work-up for causes of panhypopituitarism was mostly unremarkable: low IgG 4 (0.82, neg <1.50), indeterminate quant gold, negative HIV, low serum iron (35 mcg/dL, nl 50 – 200). Urine toxicology was positive only for opioids, reflective of the patient’s chronic pain regimen consisting of MS-Contin 60 mg twice daily and methadone 10 mg twice daily. Conclusion: This case demonstrates the potential for chronic opioid use to suppress the hypothalamic-pituitary-thyroid axis and highlights the importance of maintaining an index of suspicion for hypothyroidism in this population. Reference: (1) de Vries, F., Bruin, M., Lobatto, DJ., Dekkers, OM., Schoones, JW., van Furth, WR., Pereira, AM., Karavitaki, N., Biermasz, NR., Najafabadi, AHZ. Opioids and their endocrine effects: A systematic review and meta-analysis. JCEM. 2019. Doi: 10.1210/clinem/dgz022

Molecular interactions of thyroxine binding globulin and thyroid hormone receptor with estrogenic compounds 4-nonylphenol, 4-tert-octylphenol and bisphenol A metabolite (MBP)

AimEndocrine disruption due to environmental chemical contaminants is a global human health issue. The aim of present study was to investigate the structural binding aspects of possible interference of commonly detected environmental contaminants on thyroid function. Material and methodsThree compounds, 4-tert-octylphenol (4-tert-OP), 4-nonylphenol (4-NP), and 4-methyl-2,4-bis(4-hydroxypentyl)pent-1-ene (MBP) were subjected to induced fit docking (IFD) against thyroxine binding globulin (TBG) and thyroid hormone receptor (THR). Structural analysis included molecular interactions of the amino acid residues and binding energy estimation between the ligands and the target proteins. Key resultsAll the ligands were successfully placed in the ligand binding pocket of TBG and THR using induced fit docking (IFD). The IFD results revealed high percentage of commonality in interacting amino acid residues between the aforementioned compounds and the native ligand for both TBG and THR. The results of our study further revealed that all the compounds have the potential to interfere with thyroid transport and signaling. However, MBP showed higher binding affinity for both TBG and THR, suggesting higher thyroid disruptive potential as compared to 4-t-OP and 4-NP. Furthermore, our results also suggest that the reported disruptive effects of BPA could actually be exerted through its metabolite; MBP. SignificanceThis work implies that all the three compounds 4-NP, 4-t-OP and especially MBP have the potential to interfere with thyroid hormone transport and signaling. This potentially leads to disruption of thyroid hormone function.

Fetuin-A and thyroxin binding globulin predict rituximab response in rheumatoid arthritis patients with insufficient response to anti-TNFα.

Rheumatoid arthritis (RA) is a debilitating disease, but patient management and treatment have been revolutionized since the advent of bDMARDs. However, about one third of RA patients do not respond to specific bDMARD treatment without clear identified reasons. Different bDMARDs must be tried until the right drug is found. Here, we sought to identify a predictive protein signature to stratify patient responsiveness to rituximab (RTX) among patients with an insufficient response to a first anti-TNFα treatment. Serum samples were collected at baseline before RTX initiation. A proteomics study comparing responders and nonresponders was conducted to identify and select potential predictive biomarkers whose concentration was measured by quantitative assays. Logistic regression was performed to determine the best biomarker combination to predict good or nonresponse to RTX (EULAR criteria after 6months' treatment). Eleven biomarkers potentially discriminating between responders and nonresponders were selected following discovery proteomics. Quantitative immunoassays and univariate statistical analysis showed that fetuin-A and thyroxine binding globulin (TBG) presented a good capacity to discriminate between patient groups. A logistic regression analysis revealed that the combination of fetuin-A plus TBG could accurately predict a patient's responsiveness to RTX with an AUC of 0.86, sensitivity of 80%, and a specificity of 79%. In RA patients for whom a first anti-TNFα treatment has failed, the serum abundance of fetuin-A and TBG before initiating RTX treatment is an indicator for their response status at 6months. ClinicalTrials.gov identifier: NCT01000441. Key Points • Proteomic analysis revealed 11 putative predictive biomarkers to discriminate rituximab responder vs. nonresponder RA patients. • Fetuin-A and TBG are significantly differentially expressed at baseline in rituximab responder vs. nonresponder RA patients. • Algorithm combining fetuin-A and TBG accurately predicts response to rituximab in RA patients with insufficient response to TNFi.

Familial dysalbuminemic hyperthyroxinemia confounding management of coexistent autoimmune thyroid disease.

SummaryFamilial dysalbuminemic hyperthyroxinemia (FDH) is a cause of discordant thyroid function tests (TFTs), due to interference in free T4 assays, caused by the mutant albumin. The coexistence of thyroid disease and FDH can further complicate diagnosis and potentially result in inappropriate management. We describe a case of both Hashimoto’s thyroiditis and Graves’ disease occurring on a background of FDH. A 42-year-old lady with longstanding autoimmune hypothyroidism was treated with thyroxine but in varying dosage, because TFTs, showing high Free T4 (FT4) and normal TSH levels, were discordant. Discontinuation of thyroxine led to marked TSH rise but with normal FT4 levels. She then developed Graves’ disease and thyroid ophthalmopathy, with markedly elevated FT4 (62.7 pmol/L), suppressed TSH (<0.03 mU/L) and positive anti-TSH receptor antibody levels. However, propylthiouracil treatment even in low dosage (100 mg daily) resulted in profound hypothyroidism (TSH: 138 mU/L; FT4: 4.8 pmol/L), prompting its discontinuation and recommencement of thyroxine. The presence of discordant thyroid hormone measurements from two different methods suggested analytical interference. Elevated circulating total T4 (TT4), (227 nmol/L; NR: 69–141) but normal thyroxine binding globulin (TBG) (19.2 µg/mL; NR: 14.0–31.0) levels, together with increased binding of patient’s serum to radiolabelled T4, suggested FDH, and ALB sequencing confirmed a causal albumin variant (R218H). This case highlights difficulty ascertaining true thyroid status in patients with autoimmune thyroid disease and coexisting FDH. Early recognition of FDH as a cause for discordant TFTs may improve patient management.Learning points:The typical biochemical features of familial dysalbuminemic hyperthyroxinemia (FDH) are (genuinely) raised total and (spuriously) raised free T4 concentrations due to enhanced binding of the mutant albumin to thyroid hormones, with normal TBG and TSH concentrations.Given the high prevalence of autoimmune thyroid disease, it is not surprising that assay interference from coexisting FDH may lead to discordant thyroid function tests confounding diagnosis and resulting in inappropriate therapy.Discrepant thyroid hormone measurements using two different immunoassay methods should alert to the possibility of laboratory analytical interference. The diagnosis of FDH is suspected if there is a similar abnormal familial pattern of TFTs and increased binding of radiolabelled 125I-T4 to the patient’s serum, and can be confirmed by ALB gene sequencing.When autoimmune thyroid disease coexists with FDH, TSH levels are the most reliable biochemical marker of thyroid status. Measurement of FT4 using equilibrium dialysis or ultrafiltration are more reliable but less readily available.

Transport of the Thyroid Hormone Carrier Protein Transthyretin into Human Epidermoid Cells

ABSTRACTPurpose: Transthyretin (TTR) is a protein with a growing number of biological functions in addition to its well-established binding and circulatory transport of thyroxine, and indirect retinoid transport through interaction with retinol-binding protein. Misfolded and aggregated wild-type and mutant TTRs are involved in amyloid diseases. Several aspects of TTR pathology and physiology remain poorly understood. Receptor-mediated cellular transport of TTR has been described in a few cell types; and such studies suggest the possibility of different TTR receptors and endocytic pathways. Our main objective was to further understand the endocytic pathways for TTR.Methods: In the current study, analyses of TTR endocytic transport were performed in the human A431 cell line. The results of TTR uptake were compared with those of the iron-carrier protein transferrin (Tf, a common stardard for endocytosis studies) in the same cell types.Results: A comparison of TTR and Tf endocytosis suggested similar early, 5–10 min, accumulation kinetics. But at a later time, 30 min, TTR accumulation was 20-30% lower than that of Tf (p < .05), a result that suggests different post-endocytic fates for these two ligands. Through the use of multiple endocytosis inhibitors, biochemical evidence is provided for an internalization pathway that differs from the clathrin-mediated endocytosis of Tf.Conclusions: These results for A431 cells are compared with others reported for different cell types; and it is suggested that this same hormone carrier protein can transit into cells through multiple endocytic pathways.

Biophysical characterization and modulation of Transthyretin Ala97Ser.

ObjectiveAla97Ser (A97S) is the major transthyretin (TTR) mutation in Taiwanese patients of familial amyloid polyneuropathy (FAP), characterized by a late‐onset but rapidly deteriorated neuropathy. Tafamidis can restore the stability of some mutant TTR tetramers and slow down the progression of TTR‐FAP. However, there is little understanding of the biophysical features of A97S‐TTR mutant and the pharmacological modulation effect of tafamidis on it. This study aims to delineate the biophysical characteristics of A97S‐TTR and the pharmacological modulation effect of tafamidis on this mutant.MethodThe stability of TTR tetramers was assessed by urea denaturation and differential scanning calorimetry. Isothermal titration calorimetry (ITC) was used to measure the binding constant of tafamidis to TTR. Nuclear magnetic resonance spectroscopy (NMR) titration experiment was used to map out the tafamidis binding site.ResultsChemical and thermal denaturation confirmed the destabilization effect of A97S. Consistent with other the amyloidogenic mutant, A97S‐TTR has slightly lower conformational stability. NMR revealed the binding site of A97S‐TTR with tafamidis is at the thyroxine binding pocket. The ITC experiments documented the high affinity of the binding which can effectively stabilize the A97S‐TTR tetramer.InterpretationThis study confirmed the structural modulation effect of tafamidis on A97S‐TTR and implied the potential therapeutic benefit of tafamidis for A97S TTR‐FAP. This approach can be applied to investigate the modulation effect of tafamidis on other rare TTR variants and help to make individualized choices of available treatments for FAP patients.

Relationship of TSH with BMI in subclinical hypothyroid patients

Thyroid hormones (T3 and T4) synthesized by thyroid gland and play an essential role in normal body development and tissue metabolism. Iodine is an essential factor that is required for the synthesis of thyroid hormones. The secretion of thyroid hormones is regulated by Negative feedback mechanism. After reached in blood circulation the majority of T4 and T3 bound with carrier proteins called thyroxine binding proteins (TBG) which shows higher affinity for T4. The common diseases related to thyroid hormones include Hypothyroidism, hyperthyroidism, thyroiditis, goiter, nodes, and tumors of thyroid glands (benign and malignant). Subclinical hypothyroidism also called mild thyroid failure is defined as normal thyroid hormones but mildly elevated TSH (5 – 10 uIU/ml) with no or mild sign and symptoms. The thyroid disorders are more prevalent in females than males. Hypothyroidism is associated with obesity and various studies conducted to find out the relationship between TSH and BMI observed different finding in the particular study. In the present study, a poor positive correlation between TSH and BMI was observed in the total euthyroid subjects. A poor negative association between TSH and BMI in euthyroid males and poor positive (r value – 0.21) relationship was observed in euthyroid females. In Subclinical hypothyroid patients (total, male and female), Poor negative correlation was observed between TSH and BMI. The conclusion of this study is, as TSH increased the BMI will also increase in (mostly females) euthyroid subjects. The Inverse or poor negative correlation was observed within TSH and BMI among euthyroid males and an inverse correlation was noticed in patients with subclinical hypothyroidism.

Binding of Monovalent and Bivalent Ligands by Transthyretin Causes Different Short- and Long-Distance Conformational Changes.

The wild type protein, transthyretin (TTR), and over 120 genetic TTR variants are amyloidogenic and cause, respectively, sporadic and hereditary systemic TTR amyloidosis. The homotetrameric TTR contains two identical thyroxine binding pockets, occupation of which by specific ligands can inhibit TTR amyloidogenesis in vitro. Ligand binding stabilizes the tetramer, inhibiting its proteolytic cleavage and its dissociation. Here, we show with solution-state NMR that ligand binding induces long-distance conformational changes in the TTR that have not previously been detected by X-ray crystallography, consistently with the inhibition of the cleavage of the DE loop. The NMR findings, coupled with surface plasmon resonance measurements, have identified dynamic exchange processes underlying the negative cooperativity of binding of “monovalent” ligand tafamidis. In contrast, mds84, our prototypic “bivalent” ligand, which is a more potent stabilizer of TTR in vitro that occupies both thyroxine pockets and the intramolecular channel between them, has greater structural effects.

Square Wave Voltammetric and Computational Study of the Thyroxine-Uracil Interaction

The voltammetric behavior of Thyroxine (T4) was studied using square wave voltammetry in phosphate buffer solution at (pH 7.0) as supporting electrolyte. Thyroxine gives two well-defined reduction peaks at Ep1 (-0.359) volt and Ep2 (-1.01) volt verses (Ag/AgCl/Sat.KCl) as reference electrode. The Gibb`s free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) changes of temperature dependent on (K) were calculated using Van`t Hoff equation for Thyroxine and Uracil binding. The molecular docking between Thyroxine and Uracil has been studied, and the results indicate that the interaction between T4 and Ur was mainly hydrogen bonding and van der Waals interaction.

Management of thyroid disorders during and after pregnancy

Сучасний огляд нещодавніх рекомендацій Американської тиреоїдної асоціації та Ендокринного товариства США висвітлює найважливіші питання обстеження та ведення пацієнток із захворюваннями щитоподібної залози на тлі вагітності. Показано, що не тільки вагітність впливає на перебіг тиреоїдної патології, але й функціональні зміни тиреоїдного гормоногенезу становлять серйозну проблему для матері та плода. У вагітних під впливом плацентарного хоріонічного гонадотропіну рівень тиреотропного гормону значно знижується на 0,1–0,4 мкМО/мл для нижньої межі норми та на 1,0 мкМО/мл для верхньої у I триместрі вагітності. У зв’язку зі значним зростанням тироксин-зв’язуючих глобулінів рівні загального тироксину та трийодтироніну суттєво підвищуються з перших тижнів вагітності і можуть збільшуватися у 1,5 раза. Концентрація вільних трийодтироніну і тироксину знижується у другій половині вагітності, під час пологів вона в середньому на 10–15% нижча, ніж у загальній популяції. Часто при вагітності визначаються позитивні рівні антитіл до тиреопероксидази і тиреоглобуліну. Згідно з міжнародними клінічними стандартами не рекомендується здійснювати тотальний скринінг рівня тиреоїдних гормонів у I триместрі вагітності. Визначення тиреотропного гормону проводять лише у групах ризику наявності патології щитоподібної залози. В Україні визначення рівня цього гормону може бути рекомендоване кожній вагітній у I триместрі вагітності або на момент першого звернення. Гіпотиреоз виникає приблизно у 0,5% вагітних, а основною його причиною є аутоімунний тиреоїдит. Препаратом вибору для лікування гіпотиреозу є левотироксин. Інші препарати не мають підґрунтя для використання. Найпоширенішою причиною аутоімунного гіпертиреозу є дифузний токсичний зоб, що виникає у 0,1–1% усіх вагітностей, а серед неаутоімунних причин перше місце посідає гестаційний гіпертиреоз (1–3%). Вважається, що субклінічний гіпертиреоз будь-якого походження не потребує лікування упродовж усієї вагітності. Лікування селеном не рекомендоване жодними клінічними настановами, навіть у жінок із позитивними антитиреоїдними антитілами. Доброякісні вузли щитоподібної залози не потребують лікування впродовж вагітності, а у випадках диференційованого раку щитоподібної залози можна застосовувати помірну супресивну терапію препаратами тироксину.

The Extracellular Protein, Transthyretin Is an Oxidative Stress Biomarker.

The extracellular protein, transthyretin is responsible for the transport of thyroxin and retinol binding protein complex to the various parts of the body. In addition to this transport function, transthyretin has also been involved in cardiovascular malfunctions, polyneuropathy, psychological disorders, obesity and diabetes, etc. Recent developments have evidenced that transthyretin has been associated with many other biological functions that are directly or indirectly associated with the oxidative stress, the common hallmark for many human diseases. In this review, we have attempted to address that transthyretin is associated with oxidative stress and could be an important biomarker. Potential future perspectives have also been discussed.

Hepatocyte Early Growth Response 1 (EGR1) Regulates Lipid Metabolism in Nonalcoholic Fatty Liver Disease

ObjectiveNonalcoholic fatty liver disease (NAFLD) is a burgeoning health problem worldwide due to significant increases in the prevalence of obesity, insulin resistance diabetes, and hyperlipidemia. A risk factor for NAFLD is insulin resistance as it promotes the excessive accumulation of lipids into the hepatocytes, causing cellular stress and death. As a stress response gene, early growth response 1 (EGR1) plays critical roles in inflammation and tissue repair. The aim for this study is to explore a novel role of hepatocyte EGR1 in the regulation of lipid metabolism in NAFLD.MethodsHuman microarray data from NCBI GEO database (accession #GSE48452) was used to obtain relative EGR1 expression in human normal and NAFLD livers. To determine the expression of EGR1 during the development of NAFLD, C57Bl6/J mice were fed a high in fat, cholesterol, and fructose (HFCF) for up to 9 months and EGR1 levels were examined. An in vitro insulin stimulation experiment was performed in wild type and Egr1‐deficient primary hepatocytes to assess insulin response. In vivo hepatocyte‐specific Egr1 knockout (Egr1‐HKO) mice was accomplished in 2‐month‐old Egr1flox/flox male mice by tail vein administration of adeno‐associated viral vector 8 (AAV8) expressing cre recombinase driven by thyroxine binding globulin (TBG) promoter (AAV8‐Tbg‐Cre). An empty vector AAV8‐Tbg‐Null was included as a control. WT and Egr1‐HKO mice were fed either a normal chow or HFCF diet for 5 months and followed by the examination of body composition, adiposity, metabolic rates, insulin sensitivity, and liver histology.ResultsEGR1 was dramatically induced by insulin and abundantly expressed in the postprandial liver. The expression of EGR1 was significantly reduced in human and mouse NAFLD livers, suggesting a biological relevance of EGR1 downregulation during the pathogenesis of NAFLD. In vitro hepatocyte cultures showed that Egr1‐deficient hepatocytes have impaired activation of AKT but enhanced de novo lipogenesis in response to insulin. In vivo knockout of hepatocyte‐specific Egr1 led to liver steatosis and increased whole body adiposity under the chow diet. Additionally, in vivo EGR1 deficiency in hepatocytes exacerbated NAFLD progression by promoting liver inflammation and fibrosis in mice fed a HFCF diet.ConclusionsOur studies reveal a previously unrecognized role of hepatic EGR1 in the regulation of lipid metabolism. Our findings suggest that hepatocyte EGR1 is crucial to maintain hepatic insulin response and loss of EGR1 in hepatocytes leads to liver steatosis that exacerbates NAFLD development and progression.Support or Funding InformationNCI K22CA184146 and NIH P20 GM103549 to Yuxia Zhang.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Organophosphate triesters and selected metabolites enhance binding of thyroxine to human transthyretin in vitro

The toxicological properties of organophosphate (OP) triesters that are used as flame retardants and plasticizers are currently not well understood, though increasing evidence suggests they can affect the thyroid system. Perturbation of thyroid hormone (TH) transport is one mechanism of action that may affect thyroid function. The present study applied an in vitro competitive protein binding assay with thyroxine (T4) and human transthyretin (hTTR) transport protein to determine the potential for the OP triesters, TDCIPP (tris(1,3-dichloro-2-propyl) phosphate), TBOEP (tris(butoxyethyl) phosphate), TEP (triethyl phosphate), TPHP (triphenyl phosphate), p-OH-TPHP (para-hydroxy triphenyl phosphate), and the OP diester DPHP (diphenyl phosphate), to competitively displace T4 from hTTR. Enhancement of T4 binding to hTTR, rather than the hypothesized competition, was observed for the six OP esters and in a concentration-dependent manner. For example, T4-hTTR binding was significantly increased at concentrations of TBOEP as low as 64 nM, and up to 184% of controls at 5000 nM. A plausible explanation of these results, which to our knowledge has not been previously reported, may be allosteric interactions of the OP esters with hTTR allowing T4 to access the second site of the TH binding pocket. These in vitro results suggest a novel mechanism of OP ester toxicity via T4 binding enhancement, and possible dysregulation of T4-hTTR interactions.

Thyroid Hormones and Derivatives: Endogenous Thyroid Hormones and Their Targets.

More than a century after the discovery of L-Thyroxine, the main thyroid hormone secreted solely by the thyroid gland, several metabolites of this iodinated, tyrosine-derived ancestral hormone have been identified. These are utilized as hormones during development, differentiation, metamorphosis, and regulation of most biochemical reactions in vertebrates and their precursor species. Among those metabolites are the thyromimetically active 3,3',5-Triiodo-L-thyronine (T3) and 3,5-Diiodo-L-thronine, reverse-T3 (3,3',5'-Triiodo-L-thyronine) with still unclear function, the recently re-discovered thyronamines (e.g., 3-Iodo-thyronamine), which exert in part T3-antagonistic functions, the thyroacetic acids (e.g., Tetrac and Triac), as well as various sulfated or glucuronidated metabolites of this panel of iodinated signaling compounds. In the blood most of these hydrophobic metabolites are tightly bound to the serum distributor proteins thyroxine binding globulin (TBG), transthyretin (TTR), albumin or apolipoprotein B100. Cellular import and export of these charged, highly hydrophobic amino acid derivatives requires a number of cell-membrane transporters or facilitators such as MCT8 or MCT10 and members of the OATP and LAT families of transporters. Depending on their structure, the thyroid hormone metabolites exert their cellular action by binding and thus modulating the function of various receptors systems (e.g., ανβ3 integrin receptor and transient receptor potential channels (TRPM8) of the cell membrane), in part linked to intracellular downstream kinase signaling cascades, and several isoforms of membrane-associated, mitochondrial or nuclear thyroid hormone receptors (TR), which are members of the c-erbA family of ligand-modulated transcription factors. Intracellular deiodinase selenoenzymes, which obligatory are membrane integrated enzymes, ornithine decarboxylase and monoamine oxidases control local availability of biologically active thyroid hormone metabolites. Inactivation of thyroid hormone metabolites occurs mainly by deiodination, sulfation or glucuronidation, reactions which favor their renal or fecal elimination.

Seven Familial Dysalbuminemic Hyperthyroxinemia Cases in Three Unrelated Japanese Families and High-Performance Liquid Chromatography Analysis of the Thyroxine Binding Profile

Familial dysalbuminemic hyperthyroxinemia (FDH) is caused by abnormal human serum albumin (HSA) with an increased thyroxine (T4) affinity leading to euthyroid hyperthyroxinemia. One- and 2-step immunoassays of serum samples from FDH patients (e.g., Japanese patients) with the HSA R218P mutation can yield false-positive free thyroxine (FT4) results. Therefore, it is difficult to distinguish FDH from syndrome of inappropriate secretion of thyroid-stimulating hormone (TSH) (e.g., syndrome of resistance to thyroid hormone, TSH-producing pituitary adenoma), even when multiple assays are used. To investigate T4 to HSA binding, we examined serum samples from 7 patients from 3 Japanese families with FDH. Clinically, abnormal thyroid function tests were noted in pregnant Patient 1. Patients 2 and 3 had histories of inappropriate treatment with antithyroid drugs and surgery. All patients and affected family members were diagnosed with FDH using direct sequencing analysis. Gel filtration high-performance liquid chromatography was used for the biochemical analyses. The genomic analysis revealed a heterozygous missense mutation in HSA (R218P). In FDH patient sera, the albumin effluent corresponded to the peaks for total T4 (TT4); approximately 60% of the T4 in the effluent was detected as FT4. The results for the albumin effluent from healthy volunteer and TSHoma patient sera showed no corresponding TT4 peak. In the FDH patients, a relatively larger quantity of T4 was bound to abnormal HSA. This bound T4 was measured as FT4 during the analysis. F = free; FDH = familial dysalbuminemic hyperthyroxinemia; HPLC = high-performance liquid chromatography; HSA = human serum albumin; PCR = polymerase chain reaction; SITSH = syndrome of inappropriate secretion of TSH; T = total; T3 = triiodothyronine; T4 = thyroxine; TSH = thyroid-stimulating hormone; WT = wild-type.

Prevalence of Thyroid Disorders in Alcoholic Hepatitis Patients

Background and Aim: Thyroid hormone is maintains the metabolism of bilirubin by playing a role in the enzymatic activity of glucuronyl transferase and by regulating the level of ligandin. The liver has an important role in thyroid hormone metabolism it produces protein that bind thyroid hormone such as thyroxin binding globulin (TBG), prealbumin and albumin, it is also the major site of thyroid hormone peripheral metabolism and is involved in its conjugation of biliary excretion, oxidative deamination and extra thyroidal deiodination of thyroxin (T4) to triiodothyronine (T3). The goal of the study is to evaluate the thyroid hormone levels and liver function parameters in patients with alcoholic hepatitis. Methods: This is a retrospective, cohort study design, in which the medical records of alcoholic hepatitis patient who had been enrolled in The Institute of medical sciences BHU Varanasi from January 2015 to December 2016. The study is comparative study containing two groups (case groups is 45 alcoholic hepatitis patients aged 20–70 years and control group comprised 50 randomly selected normal subjects aged 20-70 years) For significant differences between two groups student (t) test and Chi-square test were used. Data were presented as mean ± S.D. Results: The mean serum FT4 level in patients with Alcoholic hepatitis was 7.63 ± 2.4 and in control group was 8.9 ± 1.98. The mean serum FT3 level in patients with Alcoholic hepatitis was 0.92 ± 0.37 and in control group was 1.24 ± 0.41. The mean serum TSH level in patients with Alcoholic hepatitis was 6.13 ± 3.2 and in control group was 3.79 ± 2.6. The result showed that there was a significantly increased levels of TSH and slightly decreased T3 and T4 where the P value is 0.002, 0.001 and 0.005 respectively in alcoholic hepatitis patients than normal subjects. Conclusion: The present study revealed that alcoholic hepatitis patients has more prevalent thyroid dysfunction specially hypothyroidism (Table 1).Table 1Cases n = 45Controls n = 50P valueFT3 (ng/ml)0.92 ± 0.371.24 ± 0.410.001FT4 (ng/ml)7.63 ± 2.48.9 ± 1.980.005TSH (mIU/ml)6.13 ± 3.23.79 ± 2.60.002 Open table in a new tab The authors have none to declare.

Semi-quantitative models for identifying potent and selective transthyretin amyloidogenesis inhibitors

Rate-limiting dissociation of the tetrameric protein transthyretin (TTR), followed by monomer misfolding and misassembly, appears to cause degenerative diseases in humans known as the transthyretin amyloidoses, based on human genetic, biochemical and pharmacologic evidence. Small molecules that bind to the generally unoccupied thyroxine binding pockets in the native TTR tetramer kinetically stabilize the tetramer, slowing subunit dissociation proportional to the extent that the molecules stabilize the native state over the dissociative transition state—thereby inhibiting amyloidogenesis. Herein, we use previously reported structure-activity relationship data to develop two semi-quantitative algorithms for identifying the structures of potent and selective transthyretin kinetic stabilizers/amyloidogenesis inhibitors. The viability of these prediction algorithms, in particular the more robust in silico docking model, is perhaps best validated by the clinical success of tafamidis, the first-in-class drug approved in Europe, Japan, South America, and elsewhere for treating transthyretin aggregation-associated familial amyloid polyneuropathy. Tafamidis is also being evaluated in a fully-enrolled placebo-controlled clinical trial for its efficacy against TTR cardiomyopathy. These prediction algorithms will be useful for identifying second generation TTR kinetic stabilizers, should these be needed to ameliorate the central nervous system or ophthalmologic pathology caused by TTR aggregation in organs not accessed by oral tafamidis administration.

Cavity filling mutations at the thyroxine-binding site dramatically increase transthyretin stability and prevent its aggregation

More than a hundred different Transthyretin (TTR) mutations are associated with fatal systemic amyloidoses. They destabilize the protein tetrameric structure and promote the extracellular deposition of TTR as pathological amyloid fibrils. So far, only mutations R104H and T119M have been shown to stabilize significantly TTR, acting as disease suppressors. We describe a novel A108V non-pathogenic mutation found in a Portuguese subject. This variant is more stable than wild type TTR both in vitro and in human plasma, a feature that prevents its aggregation. The crystal structure of A108V reveals that this stabilization comes from novel intra and inter subunit contacts involving the thyroxine (T4) binding site. Exploiting this observation, we engineered a A108I mutation that fills the T4 binding cavity, as evidenced in the crystal structure. This synthetic protein becomes one of the most stable TTR variants described so far, with potential application in gene and protein replacement therapies.

CSP-1103 (CHF5074) stabilizes human transthyretin in healthy human subjects

Hereditary amyloid polyneuropathy is a type of protein misfolding disease. Transthyretin (TTR) is a homotetrameric serum protein and TTR tetramer dissociation is the limiting step in amyloid fibril formation. Thus, prevention of TTR dissociation is a promising therapeutic approach and some TTR stabilizers have been approved for the treatment of TTR amyloidosis. CSP-1103 (CHF5074) is a non-steroidal anti-inflammatory derivative that lacks cyclooxygenase inhibitory activity. In vitro, CSP-1103 stabilizes the TTR tetramer by binding to the thyroxine (T4) binding site. We have previously shown that serum TTR levels were increased by oral CSP-1103 administration through stabilization of TTR tetramers in humanized mice at both the Ttr locus and the Rbp4 locus. To determine whether CSP-1103 stabilizes TTR tetramers in humans, multiple CSP-1103 oral doses were administered for two weeks to 48 healthy human volunteers in a double-blind, placebo-controlled, parallel-group study. CSP-1103 treatment stabilized TTR tetramers in a dose-dependent manner under normal or denaturing stress conditions, thereby increasing serum TTR levels. Preincubation of serum with CSP-1103 or diflunisal in vitro increased the TTR tetramer stability. Computer simulation analysis revealed that the binding affinities of CSP-1103 with TTR at pH 7.0 were similar to those of tafamidis, thus confirming that CSP-1103 has potent TTR-stabilizing activity.