Abstract
Resumo Vários fatores extratireoidianos como idade, raça, doenças concomitantes e fármacos podem influenciar na função e no diagnóstico do hipotireoidismo em cães. As alterações nas concentrações dos hormônios tireoidianos decorrentes de doenças não tireoidianas é denominada de síndrome do eutireoideo doente. O objetivo deste estudo foi avaliar a influência da leishmaniose visceral na função da tireoide em cães sem sinais de hipotireoidismo, com ou sem azotemia. Os animais positivos para leishmaniose foram divididos em seis grupos (albumina nornal ou diminuída, creatinina normal ou elevada, uréia normal ou elevada) e foi avaliado o efeito nesses grupos das concentrações séricas do hormônio estimulante da tireoide (TSH), tiroxina total (TT4) e da tiroxina livre (FT4). Os cães positivos para leishmaniose, pelo teste de ELISA, apresentaram concentrações séricas de TSH mais elevadas do que os animais soronegativos, enquanto que as concentrações de TT4 e FT4 em cães com leishmaniose foram menores (P <0,01) quando comparadas com as dos cães saudáveis. No entanto, os resultados estavam no intervalo dos valores para os animais eutireoideos. Nos cães seropositivos para leishmaniose, a TT4 apresentou diferença estatística significativa (P <0,04) no grupo com hipoalbuminemia em relação ao grupo com normoalbuminemia, respectivamente, 1,01ug/dL e 1,4ug/dL. Concluiu-se que os cães positivos para a leishmaniose visceral não desenvolveram síndrome do doente eutireóide, embora as concentrações de TT4 e a FT4 estivessem reduzida e de TSH elevada em relação aos cães sem leishmaniose.
Highlights
Alterations in thyroid hormone concentrations in response to non-thyroid illnesses (NTIs), often termed as the euthyroid sick syndrome (ESS), are well recognized in both animals and human
Parvovirosis, babesiosis, leishmaniosis, and other severe systemic diseases can cause euthyroid sick syndrome.[6,11,12,13,14] These diseases increase the production of pro-inflammatory cytokines, such as TNFα and IL-6, to cause inhibition of the hypothalamushypophysis-thyroid axis, resulting in a decrease in the production, secretion and circulation of thyroid hormones (T3 and T4).(15-17) Cytokines, such as interleukin beta 1 (IL-ß1) and 6 (IL-6) and tumor necrosis factor (TNF) have inhibitory effect on thyroid-stimulating hormone (TSH) secretion when administered to animals.[18]. This effect has been attributed to both direct actions and indirect pituitary hypothalamus
In dogs that were seropositive for leishmaniasis, no significant differences were observed among animals with increased urea and creatinine, and those with values within reference levels (Table 2)
Summary
Alterations in thyroid hormone concentrations in response to non-thyroid illnesses (NTIs), often termed as the euthyroid sick syndrome (ESS), are well recognized in both animals and human Several nonthyroid factors such as age, breed, concomitant diseases and use of certain drugs might influence the diagnosis of hypothyroidism in dogs.[1,2,3,4,5] the stress induced by non-thyroid illnesses might cause an increase of circulating glucocorticoids (prednisone, dexamethasone) and alter the thyroid function. Baseline tests to assess thyroid gland function include measurement of the TT4, FT4, reverse triiodothyronine (rT3), total (TT3) and free (FT3) triiodotirnonine, and antibody tests for lymphocytic thyroiditis.[6,10] the aim of this study was to evaluate the influence of visceral leishmaniasis on the thyroid function of dogs without signs of hypothyroidism, with or without azotemia
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