Propranolol inhibits myocardial infarction-induced brown adipose tissue D2 activation and maintains a low thyroid hormone state in rats

Considering the recognized role of thyroid hormones on the cardiovascular system during health and disease, we hypothesized that type 2 deiodinase (D2) activity, the main activation pathway of thyroxine (T4)-to-triiodothyronine (T3), could be an important site to modulate thyroid hormone status, which would then constitute a possible target for β-adrenergic blocking agents in a myocardial infarction (MI) model induced by left coronary occlusion in rats. Despite a sustained and dramatic fall in serum T4 concentrations (60-70%), the serum T3 concentration fell only transiently in the first week post-infarction (53%) and returned to control levels at 8 and 12 weeks after surgery compared to the Sham group (P<0.05). Brown adipose tissue (BAT) D2 activity (fmol T4·min-1·mg ptn-1) was significantly increased by approximately 77% in the 8th week and approximately 100% in the 12th week in the MI group compared to that of the Sham group (P<0.05). Beta-blocker treatment (0.5 g/L propranolol given in the drinking water) maintained a low T3 state in MI animals, dampening both BAT D2 activity (44% reduction) and serum T3 (66% reduction in serum T3) compared to that of the non-treated MI group 12 weeks after surgery (P<0.05). Propranolol improved cardiac function (assessed by echocardiogram) in the MI group compared to the non-treated MI group by 40 and 57%, 1 and 12 weeks after treatment, respectively (P<0.05). Our data suggested that the beta-adrenergic pathway may contribute to BAT D2 hyperactivity and T3 normalization after MI in rats. Propranolol treatment maintained low T3 state and improved cardiac function additionally.

Effects of combined interferon alpha and ribavirin therapy on thyroid functions in patients with chronic hepatitis C attending hepatitis centre Ghulam Mohammad Medical College Hospital Sukkur

To determine the frequency of thyroid dysfunction in patients of chronic hepatitis C during treatment with interferon alpha-2b and ribavirin therapy. A cohort study. Hepatitis Centre Ghulam Mohammad Mahar Medical College Hospital, Sukkur, from February 2009 to January 2010. One hundred and sixty seven non-cirrhotic chronic hepatitis C patients were grouped into treatment group [n=107] and control group [n=60] awaiting treatment. Baseline serum [s.] Alanine Transferase [ALT] and S. Aspartate Transferase [AST] were measured by IFCC method. Serum Thyroid Stimulating Hormone [S. TSH], serum free thyroxine [S. Free T4] and serum total triiodothyronine [S.T3] level were determined by chemiluminescence. Study group patients underwent 24 weeks IFN and ribavirin therapy and were followed-up for thyroid dysfunction at weeks 0, 12 and 24. Control group patients underwent the same tests at weeks 0, 12 and 24. Statistical analysis was done on SPSS 15. Out of 107 patients of treatment group, 20 patients [18.69%] developed thyroid dysfunction. Females were at higher risk with Relative Risk [RR] of 11.25 and Attributable Risk [AR] of 91%. Hypothyroidism was more common than hyperthyroidism. Interferon-alpha and ribavirin therapy induces thyroid dysfunction in chronic hepatitis C patients. Hypothyroidism was more common. Females are at a higher risk of developing thyroid dysfunction

Treating primary hypothyroidism with weekly doses of levothyroxine: a randomized, single-blind, crossover study / Tratamento de hipotiroidismo primário com doses semanais de levotiroxina: um estudo randomizado, unicego, crossover

OBJECTIVE: Compliance to levothyroxine treatment in hypothyroidism is compromised by daily schedule, and a weekly dose may be an alternative. SUBJECTS AND METHODS: This was a randomized, crossover study. Fourteen females were assigned to daily or weekly doses of LT4. After six weeks, they switched regimens. Thyroid parameters were measured at baseline, and after 42 and 84 days. Echocardiogram and hyperthyroidism symptoms were evaluated before and four hours after LT4 intake. RESULTS: In the weekly dose treatment, fT4 levels were higher after taking LT4, and lower seven days after the last dose; by the 6th week there was a small decrease in T3 levels. TSH remained unchanged and there were no hyperthyroidism symptoms or echocardiographic manifestations. CONCLUSION: Weekly dose leads to transient increases in fT4, without hyperthyroidism or cardiac symptoms. That approach seems to be a safe alternative for the treatment of hypothyroidism.

OBJETIVO: Aderência ao tratamento do hipotiroidismo é comprometido pelo uso diário de levotiroxina, e doses semanais poderiam ser uma alternativa. SUJEITOS E MÉTODOS: Este é um estudo randomizado, crossover. Quatorze mulheres foram selecionadas para receber LT4 diariamente ou semanalmente. Após seis semanas, houve inversão do regime de tratamento. Avaliações tireoideanas foram realizadas antes, após 42 e 84 dias. Avaliação de sintomas de hipertireoidismo e ecocardiograma foi realizada antes e após quatro horas de LT4. RESULTADOS: Com dose semanal, os níveis de fT4 foram mais elevados logo após a dose de LT4, e menores após sete dias; após seis semanas, houve diminuição de T3. TSH permaneceu inalterado e não houve manifestações ecocardiográficas ou de hipertireodismo. CONCLUSÃO: Dose semanal de LT4 leva à elevação de fT4, sem manifestações de hipertireoidismo, e parece ser uma alternativa segura para o tratamento do hipotireoidismo.

Effect of conjugated equine estrogens and tamoxifen administration on thyroid gland histomorphology of the rat

OBJETIVO: Avaliar a ação dos estrogênios conjugados eqüinos e do tamoxifeno na histomorfologia da tireóide de ratas. MÉTODO: Estrogênios conjugados eqüinos são ministrados clinicamente como terapia estrogênica e contêm formulação complexa com muitos tipos de estrogênios que diminuem os sintomas da pós-menopausa. Trinta ratas adultas ooforectomizadas foram divididas aleatoriamente em três grupos: GI – veículo (propilenoglicol); GII - ECE 200 µg/Kg por dia; e GIII – TAM 1 mg/Kg por dia. Acrescentou-se ainda um grupo de 10 animais com os ovários intactos e tratados com veículo (GIV). Todos os animais foram tratados por gavagem durante 50 dias consecutivos, ao final foram coletadas amostras do sangue e a tireóide removida e processada para análise morfológica e imunohistoquímico para avaliar o PCNA. RESULTADOS: A maior altura das células foliculares foi observada nos animais tratados com ECE (14,90 ± 0,20 µm), TAM (14,90 ± 0,10 µm) e no grupo com ovários intactos (15,10 ± 0,50 µm), comparando-se aos controles ovariectomizados (GI) (9,90 ± 0,20 µm) (p<0,001). A maior área folicular foi detectada nos grupos tratados com ECE (2.225 ± 51 µm2) e com TAM (2.127 ± 67 µm2), comparado ao veículo (5.016 ± 53 µm2) em animais ooforectomizados. Os níveis de T4 e T3 nos grupos tratados com ECE, com TAM e no grupo com ovários intactos foram maiores do que no grupo tratado com veículo (p<0,001). O índice do PCNA no grupo tratado com veículo foi menor do que em todos os outros grupos. CONCLUSÃO: Nossos dados sugerem que a administração de ECE e TAM resulta em atividade proliferativa na tireóide.

Alteraciones en la regulación de tirotrofina en el hipotiroidismo congénito / Thyrotropin regulation impairments in congenital hypothyroidism

La TSH constituye uno de los marcadores más importantes para el diagnóstico y control del tratamiento de pacientes con hipotiroidismo congénito (HC). Por otra parte, es conocido desde hace muchos años que algunos niños con HC presentan desde el nacimiento una alteración del umbral de sensibilidad de su unidad hipotálamo-hipofisaria, con niveles elevados de TSH a pesar de una sustitución apropiada. Sin embargo, no existen referencias sobre alteraciones de estas características desarrolladas tardíamente en la evolución del HC. En los últimos 20 años se evaluaron 8 pacientes (7 y 1 ) que presentaban esta situación clínica con diagnóstico etiológico de disenzimia (alteración de la organificación) en 4 casos, disgenesia en 4. La edad cronológica (EC) al diagnóstico e inicio del tratamiento fue de (x y rango): 3,25 (1-8) meses y los valores pretratamiento (mediana y rango) fueron: T4 (µg/dl) = 1,28 (0,2-2,8); TSH = 50 (27-250) mUI/l. La dosis media de T4 utilizada a partir del primer año de vida fue 3,95 (3,03-6,30) µg/kg/día. Bajo tratamiento sustitutivo los pacientes mantuvieron niveles normales para su EC de T3, T4 y TSH durante 7,1 (3,2-10,4) años, a partir del cual presentaron elevación de la TSH a pesar que sus hormonas tiroideas se encontraban en el rango normal: T3 (ng/dl) = 136 (105-180), T4 = 11,1 (8,4-12,0), T4l (ng/dl) = 1,9 (1,4-2,0), TSH basal = 23,5 (14-45,5), TSH post TRH = 55 (40-90). El seguimiento de los pacientes a partir de detectarse la secreción inapropiada de TSH fue de 6,3 (2,8-9,6) años, no constatándose normalización durante dicho período en ninguno de ellos. En todos los casos se incrementó la opoterapia alcanzando valores suprafisiológicos de T4: 13,38 (12,5-15,1) y T4l: 2,16 (2,1-2,3), con manifestaciones de sobredosificación en algunos, obteniéndose la normalización de la TSH basal y post TRH sólo en 2 de ellos. El diagnóstico por imágenes de la región selar no mostró alteraciones en ninguno. En 6 casos se asoció TRIAC al tratamiento con T4 en una dosis de 350 µg (8,1-14,6 µg/kg) con lo que se obtuvo normalización de los niveles de TSH en todos ellos; no constatándose ningún efecto indeseable. Se concluye: * Parecería existir un subgrupo de pacientes con HC quienes desarrollan tardíamente una alteración en la regulación de TSH. * Esto podría reflejar una alteración adquirida en el mecanismo de regulación de la TSH, posiblemente vinculada a una relativa insensibilidad a la T4...

Alterations of the rat thyroid gland under experimental conditions

The thiyroid gland of rats, was studied under experimental conditions porvided by administration of several doses of lithium carbonate. It was noted a drug a cumulative effcct on the serum; and the decrease of T3 and T4 hormones in the blood, as well as, the red blood cells, hemoglobin, hematocrit platelets and leukocytes; the diameter of the thy roid follicles, the size of the follicular cells and colloid droplets. On the othcr hand the stroma was invaded by of collagen fibers and blood capillaries.