Effect of natural neosporosis on levels of testosterone and thyroid hormones in bulls

Present study was aimed to investigate the effect of Neospora caninum seropositivity on testosterone and thyroid hormones levels of Iranian bulls. Two groups containing bulls with neosporosis and bulls without neosporosis were considered. To achieve bulls with neosporosis, N. caninum agglutination test (NAT) and ELISA was performed. Testosterone, thyroxin (T4) and tri-iodothyronine (T3) levels were measured and compared between infected and non-infected bulls. Testosterone of bulls with neosporosis was decreased but the difference was not significant. Serum T4 of bulls with neosporosis was decreased significantly but changes of serum T3 was not significant. The hypothalamic–pituitary–adrenal axis (HPA axis) impairment, direct effect of N. caninum and its antigens on testis function, interrelationships between thyroid dysfunction and hypogonadism, adaptive response of infected animals to N. caninum and occurrence of oxidative stress in testis due to the presence of Neospora may be the reasons of hormonal changes. The effect of N. caninum on hormonal changes remains incomplete at present and is an area for future research so as to better characterize the effects and mechanisms