The Transcription Factor NF-κB Mediates Thyrotropin-Stimulated Expression of Thyroid Differentiation Markers.

Background: The nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcription factor is a key regulator of cell survival, proliferation, and gene expression. Although activation of NF-κB signaling in thyroid follicular cells after thyrotropin (TSH) receptor (TSHR) engagement has been reported, the downstream signaling leading to NF-κB activation remains unexplored. Here, we sought to elucidate the mechanisms that regulate NF-κB signaling activation in response to TSH stimulation. Methods: Fisher rat-derived thyroid cell lines and primary cultures of NF-κB essential modulator (NEMO)-deficient mice thyrocytes were used as models. Signaling pathways leading to the activation of NF-κB were investigated by using chemical inhibitors and phospho-specific antibodies. Luciferase reporter gene assays and site-directed mutagenesis were used to monitor NF-κB-dependent gene transcriptional activity and the expression of thyroid differentiation markers was assessed by reverse transcription quantitative polymerase chain reaction and Western blot, respectively. Chromatin immunoprecipitation (ChIP) was carried out to investigate NF-κB subunit p65 DNA binding, and small interfering RNA (siRNA)-mediated gene knockdown approaches were used for studying gene function. Results: Using thyroid cell lines, we observed that TSH treatment leads to protein kinase C (PKC)-mediated canonical NF-κB p65 subunit nuclear expression. Moreover, TSH stimulation phosphorylated the kinase TAK-1, and its knockdown abolished TSH-induced NF-κB transcriptional activity. TSH induced the transcriptional activity of the NF-κB subunit p65 in a protein kinase A (PKA)-dependent phosphorylation at Ser-276. In addition, p65 phosphorylation at Ser-276 induced acetyl transferase p300 recruitment, leading to its acetylation on Lys-310 and thereby enhancing its transcriptional activity. Evaluation of the role played by NF-κB in thyroid physiology demonstrated that the canonical NF-κB inhibitor BAY 11-7082 reduced TSH-induced expression of thyroid differentiation markers. The involvement of NF-κB signaling in thyroid physiology was confirmed by assessing the TSH-induced gene expression in primary cultures of NEMO-deficient mice thyrocytes. ChIP and the knockdown experiments revealed that p65 is a nuclear effector of TSH actions, inducing the transcripcional expression of thyroid differentiation markers. Conclusions: Taken together, our results point to NF-κB being a pivotal mediator in the TSH-induced thyroid follicular cell differentiation, a relevant finding with potential physiological and pathophysiological implications.

Relationship of gender and age on thyroid hormone parameters in a large Chinese population

ABSTRACT Objective This study aimed to present the impact of age and gender on thyroid hormone levels in a large Chinese population with sufficient iodine intake. Subjects and methods A total of 83643 individuals were included and were stratified by age and gender. The median, 2.5th and 97.5th of thyrotropin (TSH), free triiodothyronine (FT3), free thyroxine (FT4) and FT3/FT4 ratio were calculated for both genders for every decade from 18 to over 80 years. TSH, FT3, FT4, FT3/FT4 distribution in each age group was evaluated for females and males using smoothing splines in the generalized additive models (GAM). TSH concentrations were compared in the different age groups in gender. Results In the over 80s age group, the TSH level (median: 2.57 mIU/L, 2.5th-97.5th: 0.86-7.56 mIU/L) was significantly higher than other age groups, irrespective to gender (P<0.001). Females had a higher TSH value than males in all age groups (P<0.001). Results of the smoothing curves showed that TSH increased with age, FT3 concentration was higher in males than in females and the tendency of the FT3/FT4 ratio was basically similar to that of FT3. TSH concentration in the 50s age group (median 2.48 mIU/L for females versus 2.00 mIU/L for males) was significantly higher than that in the 30s age group (median 2.18 mIU/L for females versus median 1.85 mIU/L for males). Conclusions In accord with increasing TSH values during aging, females and older adults have lower FT3 values and lower FT3/FT4 ratios, while the FT4 values remain stable.

Tanycytes and the Control of Thyrotropin-Releasing Hormone Flux Into Portal Capillaries.

Central and peripheral mechanisms that modulate energy intake, partition and expenditure determine energy homeostasis. Thyroid hormones (TH) regulate energy expenditure through the control of basal metabolic rate and thermogenesis; they also modulate food intake. TH concentrations are regulated by the hypothalamus-pituitary-thyroid (HPT) axis, and by transport and metabolism in blood and target tissues. In mammals, hypophysiotropic thyrotropin-releasing hormone (TRH) neurons of the paraventricular nucleus of the hypothalamus integrate energy-related information. They project to the external zone of the median eminence (ME), a brain circumventricular organ rich in neuron terminal varicosities and buttons, tanycytes, other glial cells and capillaries. These capillary vessels form a portal system that links the base of the hypothalamus with the anterior pituitary. Tanycytes of the medio-basal hypothalamus express a repertoire of proteins involved in transport, sensing, and metabolism of TH; among them is type 2 deiodinase, a source of 3,3',5-triiodo-L-thyronine necessary for negative feedback on TRH neurons. Tanycytes subtypes are distinguished by position and phenotype. The end-feet of ß2-tanycytes intermingle with TRH varicosities and terminals in the external layer of the ME and terminate close to the ME capillaries. Besides type 2 deiodinase, ß2-tanycytes express the TRH-degrading ectoenzyme (TRH-DE); this enzyme likely controls the amount of TRH entering portal vessels. TRH-DE is rapidly upregulated by TH, contributing to TH negative feedback on HPT axis. Alterations in energy balance also regulate the expression and activity of TRH-DE in the ME, making ß2-tanycytes a hub for energy-related regulation of HPT axis activity. ß2-tanycytes also express TRH-R1, which mediates positive effects of TRH on TRH-DE activity and the size of ß2-tanycyte end-feet contacts with the basal lamina adjacent to ME capillaries. These end-feet associations with ME capillaries, and TRH-DE activity, appear to coordinately control HPT axis activity. Thus, down-stream of neuronal control of TRH release by action potentials arrival in the external layer of the median eminence, imbricated intercellular processes may coordinate the flux of TRH into the portal capillaries. In conclusion, ß2-tanycytes appear as a critical cellular element for the somatic and post-secretory control of TRH flux into portal vessels, and HPT axis regulation in mammals.

Subclinical Hypothyroidism and Intracytoplasmic Sperm Injection Outcomes / Hipotireoidismo subclínico e resultados de Injeção intracitoplasmática de espermatozoide

Abstract Purpose Whether preconception elevated concentrations of thyroid-stimulating hormone (TSH) compromises reproductive outcomes in patients undergoing assisted reproduction techniques (ARTs) remains unclear. This study therefore compared the reproductive outcomes in patients with TSH concentrations of < 2.5 mIU/L, 2.5-4.0 mIU/L, and 4.0-10.0mIU/L undergoing controlled ovarian stimulation (COS) for in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI). Methods This retrospective cohort study evaluated the medical records of all women with measured TSH concentrations who underwent IVF/ICSI between January 2011 and December 2012. The patients were divided into three groups: TSH < 2.5mIU/L (group 1); THS ≥2.5 and < 4.0 mIU/L (group 2); and THS ≥4 mIU/L and < 10.0 mIU/L (group 3). Patients who were administered levothyroxine for treating hypothyroidism were excluded from the analysis. The primary endpoints were clinical pregnancy,miscarriage, live birth and multiple pregnancy rates. Results During the study period, 787 women underwent IVF/ICSI. Sixty were excluded because their TSH concentrations were unavailable, and 77 were excluded due to their use of levothyroxine. The prevalence of patients presenting elevated concentrations of TSHwas of 5.07% (using a TSH threshold of 4.0 mIU/L) and of 29.99% (using a TSH threshold of 2.5 mIU/L). Patient characteristics, type of COS, and response to COS did not differ among the three groups, and there were no differences in clinical pregnancy (24.4% versus 25.9% versus 24.2%, p = 0.93); miscarriage (17.1% versus 14.3% versus 12.5%, p = 0.93); live birth (20.2% versus 22.2% versus 21.2%, p = 0.86); and multiple pregnancy rates (27.0% versus 21.4% versus 25.0%, p = 0.90) respectively. Conclusion Response to COS, live birth, and miscarriage rates were not altered in women with elevated concentrations of TSH undergoing IVF/ICSI, regardless of using a TSH threshold of 2.5mIU/L or 4.0mIU/L. These findings reinforce the uncertainties related to the impact of subclinical hypothyroidism on reproductive outcomes in women undergoing COS for ARTs.

Resumo Objetivos Se concentrações elevadas de hormônio estimulante da tireoide (TSH) antes do parto comprometem resultados reprodutivos em pacientes submetidas a técnicas de reprodução assistida (TRA) é incerto. Este estudo comparou resultados reprodutivos de pacientes com concentrações de TSH < 2,5 mIU/L; 2,5-4,0 mIU/L e 4,0-10,0 mIU/L submetidas a estimulação ovariana controlada (EOC) para fertilização in vitro (FIV)/injeção intracitoplasmática de espermatozoide (ICSI). Métodos Este estudo de coorte retrospectiva avaliou prontuários médicos de todas as pacientes que tinham registro de concentrações de TSH submetidas a FIV/ICSI entre janeiro de 2011 e dezembro de 2012. As pacientes foram divididas em três grupos: aquelas com TSH < 2,5 mIU/L (grupo 1); entre 2,5 e 4,0 mIU/L (grupo 2) e entre 4,0 mIU/L e 10,0 mIU/L (grupo 3). As pacientes que estavam em uso de levotiroxina para tratamento de hipotireoidismo foram excluídas da análise. Os desfechos primários foram taxas de gravidez clínica, de abortamento, de nascido vivo e de gravidez múltipla. Resultados Durante o período do estudo, 787 mulheres foramsubmetidas a FIV/ICSI. Sessenta foram excluídas por causa da indisponibilidade das concentrações de TSH, e 77 foram excluídas porque estavam usando levotiroxina. A prevalência de pacientes apresentando elevação das concentrações de TSH foi de 5,07% (usando um limite de TSH de 4,0 mIU/L) e 29,99% (usando um limite de TSH de 2,5 mIU/L). As características das pacientes, tipo de EOC e reposta à EOC não diferiram entre os três grupos, nem houve diferenças nas taxas de gravidez clínica (24,4% versus 25,9% versus 24,2%, p = 0,93); abortamento (17,1% versus 14,3% versus 12,5%, p = 0,93); nascido vivo (20,2% versus 22,2% versus 21,2%, p = 0,86); e taxas de gestação múltipla (27,0% versus 21,4% versus 25,0%, p = 0,90), respectivamente. Conclusão Resposta à EOC, taxa de nascido vivo e de abortamento não foram alteradas em mulheres submetidas a FIV/ICSI com concentrações elevadas de TSH independente de usar um limite de 2,5 ou 4,0 mIU/L. Estes achados reforçam as incertezas relacionadas ao impacto do hipotireoidismo subclínico nos resultados reprodutivos de mulheres submetidas a EOC para TRA.

Importancia de la detección de ATPO y ATg en pacientes con TSH entre 2, 5 a 4, 5 mU/L y su prevalencia en el Hospital Aeronáutico Córdoba / Importance of detection of anti-TPO and ATG in patients with TSH values between 2.5 and 4.5 mU/l and their prevalence at the Hospital Aeronáutico Córdoba

Introducción: La enfermedad tiroidea autoinmune (EAT) causa daño celular y altera la función tiroidea por acción de los anticuerpos antitiroperoxidasa (ATPO) y antitiroglobulina (ATg).Estudios longitudinales demuestran que personas con tirotrofina (TSH) entre 2,5 a 4,5 mU/L y autoanticuerpos tiroideos (ATPO y ATg) positivos tienen un riesgo aumentado de desarrollar hipotiroidismo franco, definiendo a esta población como una categoría de riesgo intermedio. Objetivo: destacar la importancia de la detección de anticuerpos antitiroideos en la población con TSH entre 2,5 a 4,5 mU/L y conocer su prevalencia en la población del Hospital Aeronáutico Córdoba. Materiales y métodos: se midió ATPO y ATg a 216 muestras depacientes mayores a 20 años con TSH entre 2,5 a 4,5 mU/L que concurrieron al laboratorio del Hospital Aeronáutico Córdoba y se excluyeron a las mujeres embarazadas, aquellos pacientes condopajes previos de TSH mayores a 2,5 mU/L y aquellos bajo tratamiento con levotiroxina. Las determinaciones se realizaron por el inmunoanálisis quimioluminiscente de micropartículas (CMIA). Resultados: se observó mayor prevalencia del sexo femenino, aumentando con la edad y la presencia de un 30% de pacientes con anticuerpos antitiroideos positivos en la población estudiada Se demostró que es más frecuente la presencia de ATPO que de ATg y que no hay diferencia significativa entre el dosaje de ATPOy ATg en conjunto y ATPO como única medida. Conclusiones: se recomienda valorar la presencia de anticuerpos antitiroideos, principalmente ATPO, en las poblaciones más susceptibles: pacientes con TSH entre 2,5 – 4,5mU/L, mujeres mayores a 60 años y embarazadas.

Introduction: Autoimmune thyroid disease (EAT) causes cellulardamage and alters thyroid function by the action of anti thyroid peroxidase antibodies (ATPO) and anti thyroglobulin(ATg). Longitudinal studies show that people with thyrotropin (TSH) between 2.5 to 4.5 mU/L and positive thyroid autoantibodies (ATPO and ATg) have an increased risk of developing overthypothyroidism, defined this population as intermediate risk category.Objective: Highlight the importance of the detection of antithyroid antibodies in the population with TSH between 2.5 to 4.5 mU/L and determine their prevalence in the population of HospitalAeronáutico Córdoba. Materials and methods: We measured ATg and ATPO in 216 samples of patients aged over 20 years with TSH between 2.5 to 4.5 mU/L who attended the Hospital Aeronáutico Córdoba laboratory and excluded pregnant women, patients with previousdoping TSH greater than 2.5 mU/L and those treated with levothyroxine. Determinations were performed by thechemiluminescent microparticle immunoassay (CMIA). Results: We observed a higher prevalence of female gender, increasing with age and the presence of 30% of patients withpositive antithyroid antibodies in this population. We proved that ATPO is more frequent than ATg and there was no significant.