Evaluation of relationship between thyroid hormones and testosterone as well as some of the blood serametabolites in breeding and out-breeding seasons in the Arabian stallion

BAKGROUND: In most mammalian reproductive activities are closely related to the thyroid gland.
This experiments were conducted in order to evaluate the correlations between T3, T4 and T3uptak values with testosterone and some of the blood serum metabolites including glucose, cholesterol and triglyceride.
Blood samples were collected from jugular vein of 21 healthy purebred Arabian stallion 2-14 years of age in breeding (July) and out-breeding (January) seasons under the same management and feeding programs during the experiment. After centrifuging the blood samples and serum separation, the concentrations of T3, T4 and T3uptak hormones as well as testosterone were measured by standard radio immunoassay, while serum metabolites were measured using enzymatic calorimetric method. Also, FTI values were calculated and reported. Data were analyzed using the Pearson Bivariate Correlation test by SPSS software program.
Results of the study showed that in breeding season, there was a significant positive correlation between T4 and FTI with testosterone concentrations (P0.05). In out-breeding season, there was a significant negative correlation between T3 and cholesterol, FTI and glucose, T4 with glucose and cholesterol (P0.05).
CONCIUSIONS: The experiment showed that the correlation between thyroid hormones and breeding season in the Arab stallion.