Age-related changes in testicular parameters and their relationship to thyroid hormones and testosterone in male Murrah buffaloes

Abstract

Abstract. The present study aims to investigate the age-related changes in testicular parameters and their association with plasma triiodothyronine (T3), thyroxine (T4), and testosterone in male Murrah buffaloes. Testicular measurements and single blood samples were collected from male Murrah buffaloes (n= 103) aged between 6 months and 8 years. The correlation coefficients of average testicular length (ATL), paired testis width (PTW), and scrotal circumference (SC) in relation to age were 0.88, 0.91, and 0.90, respectively. The regression equation between testicular weight (TW) and age was Y=1.48×x0.005 (r= 0.90; R2= 0.79). Plasma T4 and testosterone increased significantly (p< 0.001) with age and their levels ranged between 12.9 and 41.8 and 0.05 and 1.48 ng mL−1, respectively. With respect to associations between testicular parameters and plasma hormone levels, we observed significant (p< 0.01) correlations between ATL, PTW, SC, TW, and plasma T4. A significant correlation (r= 0.31; p< 0.01) between plasma T4 and testosterone levels was also observed. However, the correlations between plasma T3 and testicular parameters and plasma T3 and testosterone were non-significant. From the present study, we conclude that plasma T4 is positively correlated with testicular parameters and plasma testosterone, indicating its role in testis development and steroidogenesis.