ABSTRACT
To investigate the effect of special meterological condition of Ahwaz on thyroid function and to study the effects of gender and age on the function of this gland.Cross sectional study. 210 Sheep.By Considering the meteorologic condition of Ahwaz and biseasonally nature of year in the region, blood samples of 210 sheep were randomly collected during the warmest [February] and coldest [July] months of year from Ahwaz slaughterhouse. Serum T3, T4, T3 uptake and free thyroxin index [FTI] concentrations were measured in four age groups of sheep: less than 6 months, 6-12 months, 12-48 months and above 48 months by Radioimmunoassay. Analysis of variance and Correlation coefficient.There was a significant differences in the concentration of serum T3 [P<0.001], T4 [P<0.001], T3 uptake [P<0.001] and FTI [P<0.05] between the warmest and coldest months. Furthermore, age [but not sex] showed significant effect on these parameters [P<0.05]. Serum T3, T4 and FTI levels was significantly higher and T3 uptake was significantly lower in February than July. A direct correlation between T4 and FTI, T4 and T3, FTI and T3, T3 Uptake and FTI in each month [P<0.01] and a reverse correlation between T3 and T3 uptake [P<0.05] were noticed.The results of this study showed that in July, heat had a suppression effect on thyroid function in sheep. Therefore increased production and reproduction problems in warm season may be due to thyroid dys function. While age showed a negative correlation with thyroid gland function, such pattern did not found for sex