In the present study, LH levels were increased in the bull calves of all the three age groups but significant (p < 0.0001) amounts of testosterone was produced only in Group I (14–16 months of age) bull calves whereas Mongkonpunya et al. (1975) observed testosterone levels as high as 5.30 ng/ml in 6 months old HF bull calves after administration of exogenous GnRH. The gene discussed is GNRH1; the disease is hydrops fetalis.