The effect of ambient temperature on thyroid hormones concentration and histopathological changes of thyroid gland in cattle in Tabriz, Iran.

摘要

To identify the thyroid histological and hormonal changes in response to ambient temperature variations, thyroid glands and blood samples were randomly collected from 800 indigenous corssbred cattle of both sex and different age groups from municipal Tabriz slaughter house in Iran. The extent of fluctuations in triiodothyronine (T₃), thyroxin (T₄), T₃ uptake and thyroid histopathological lesions were scrutinized in 2 months in year 2007, viz., February (the coldest month) and August (the hottest month). A marked decline was discernable in T₃, T₄ and T₃ uptake in August compared to February. Out of 800 pairs of thyroid glands, 120 (15%) had lesions in which histopathological changes were categorized as follicular atrophy (2.5%), Paranchymal cyst (1.38%), colloid goitre (3.39%), follicular cell hyperplasia (0.27%), thyroid fibrosis (0.635%), focal hyperplastic goitre (0.88%), diffuse hyperplastic goitre additional paranchymal cyst (0.63%). Mean of thyroidal parameters for T₄, T₃ and T₃ uptake was lower in lesioned group (p<0.01). The frequency of lesioned thyroid was higher in summer than winter (p<0.001). The result of this study showed that high ambient temperature has profound effect on thyroid function, secretion and pathological changes in cattle.