Tiroiditis no-autoinmunes / Non-autoimmune thyroiditis

El término tiroiditis comprende un grupo de enfermedades de la glándula tiroides caracterizado por la presencia de inflamación, abarcando entidades autoinmunes y no-autoinmunes. Pueden manifestarse como enfermedades agudas con dolor tiroideo severo (tiroiditis subaguda y tiroiditis infecciosas), y condiciones en las cuales la inflamación no es clínicamente evidente, cursando sin dolor y presentando disfunción tiroidea y/o bocio (tiroiditis inducida por fármacos y tiroiditis de Riedel). El objetivo de esta revisión es aportar un enfoque actualizado sobre las tiroiditis no-autoinmunes cubriendo sus aspectos clínicos, diagnósticos y terapéuticos.

The term thyroiditis comprises a group of thyroid diseases characterized by the presence of inflammation, including autoimmune and non-autoimmune entities. It may manifest as an acute illness with severe thyroid pain (subacute thyroiditis and infectious thyroiditis), and conditions in which the inflammation is not clinically evident evolving without pain and presenting primarily thyroid dysfunction and/or goiter (drug-induced thyroiditis and Riedel thyroiditis). The aim of this review is to provide an updated approach on non-autoimmune thyroiditis and its clinical, diagnostic and therapeutic aspects.

El litio y su relación con la acuaporina-2 y el canal de sodio ENaC / Lithium and its relation with the epithelial sodium channel and aquaporin-2

Desde hace más de cuarenta años que el litio es usado para el tratamiento de la enfermedad bipolar; recientes estudios sugieren también su utilidad en el trastorno cognitivo mínimo tipo amnésico. El litio es filtrado en el glomérulo y un 65-75% del mismo es reabsorbido en el túbulo contorneado proximal y en el asa ascendente de Henle por el transportador Na+, K+, 2Cl- y vía paracelular. Una pequeña fracción del litio entra en las células principales del túbulo colector por medio del canal epitelial de sodio sensible al amiloride (ENaC) localizado en la membrana apical de la célula. Luego de 10- 20 años de tratamiento con litio los enfermos pueden desarrollar poliuria, acidosis tubular e insuficiencia renal crónica que puede terminar en una forma de diabetes que no responde a la arginina vasopresina llamada diabetes insípida nefrogénica. Se cree que estas fallas renales son consecuencias de una reducción en el número de moléculas de acuaporina 2 en la membrana apical. Las causas para esto son complejas. El litio es un poderoso inhibidor de la isoforma beta de la enzima glicógeno sintetasa quinasa y esto está asociado a una menor actividad de la adenilato ciclasa que lleva a una disminución en la concentración intracelular de cAMP. Esto finalmente interferiría con la síntesis de nuevas moléculas de acuaporina 2 y con el tráfico de ellas desde la zona subapical de la célula hacia la membrana celular, causando la disminución en la reabsorción de agua en la parte distal del nefrón.

For more than 40 years lithium has been used to treat bipolar disorder and recent trials suggest a potential efficacy also in the treatment of the amnestic mild cognitive impairment. Lithium is filtered by the glomerulus and 65% - 75% of the filtered amount is reabsorbed along the proximal tubule and in the thick ascending limb of Henle's loop by the Na+, K+, 2Cl- transporter and via paracellular. A small fraction of lithium is reabsorbed in the collecting duct's principal cells through the epithelial Na channel (ENaC) located on the apical side of the cells. Polyuria, renal tubular acidosis and chronic renal failure are the most frequent adverse effects of lithium after 10-20 years of treatment and these alterations can reach to a vasopressin nonresponding form of diabetes insipidus entity called nephrogenic diabetes insipidus. It is believed that the molecular mechanisms of these renal changes are related to a reduction in the number of aquaporin-2 inserted in the apical membrane of the cells. The causes of this are complex. Lithium is a powerful inhibitor of the enzyme glycogen synthase kinase 3β and this is associated with a lower activity of adenylate cyclase with a reduction in the cAMP levels inside of the cells. The latter may interfere with the synthesis of aquaporin-2 and also with the traffic of these molecules from the subapical site to membrane promoting the impairment of water reabsorption in the distal part of the kidney.

Endocrine disturbances related to the use of lithium / Distúrbios endocrinológicos relacionados ao uso de lítio

Despite recent advances in pharmacological treatment of psychiatric disorders, lithium salts remain frequently used, as they are effective and inexpensive alternatives, especially in the treatment of bipolar disorders. Their use is commonly associated with various endocrine disorders, mainly in thyroid and parathyroid function, and in mineral metabolism. This article aims at reviewing these potential endocrinopathies related to the use of lithium to make health care professionals aware and familiar with these possible complications when they follow up patients using this drug, and to make them able to monitor, identify and institute early and appropriate treatment.

Apesar dos recentes avanços farmacológicos no tratamento dos transtornos psiquiátricos, os sais de lítio permanecem como uma alternativa eficaz e de menor custo, sendo usados com frequência principalmente no tratamento dos transtornos bipolares. O seu uso é comumente relacionado com diversas alterações endocrinológicas, principalmente nas funções tiroidiana, paratiroidiana e do metabolismo iônico. Este artigo tem por objetivo fazer uma revisão dessas potenciais endocrinopatias relacionadas ao uso do lítio, para que, no seguimento de pacientes em uso dessa medicação, os profissionais de saúde estejam atentos e familiarizados com essas possíveis complicações, conseguindo identificar e instituir tratamento precocemente.

Lithium-induced sinus node dysfunction at therapeutic serum levels.

Lithium-induced cardiotoxicity, though rare at therapeutic levels, has been reported frequently in overdoses. We report a patient who developed sinus bradycardia while being treated with lithium carbonate even though the serum lithium levels were within the therapeutic range. It reversed following withdrawal of lithium and did not reappear with subsequent treatment with valproate.

Drug-induced thyroid disorders.

Disorders of thyroid hormone metabolism are commonly encountered in clinical practice. Apart from conditions affecting the thyroid gland, thyroid hormone homeostasis may be altered by medications used in varied clinical settings. Drugs may interfere at different steps in thyroid hormone synthesis or secretion leading to hypothyroidism or thyrotoxicosis or may cause changes in hormone binding leading to difficulties in the interpretation of thyroid function tests. These difficulties have been largely overcome by the development of improved diagnostic tools including radio-active uptake studies, estimation of thyroid auto-antibodies and highly sensitive hormone assays.