This study analyzes lead effects in gonadotropins, testosterone, estradiol and progesterone secretion. Lead was applied by intraperitoneal doses of 0.0036 mg/kg/day (TDI), 2,61 mg/kg/day (intermediate) and 4,95 mg/kg/day (LD 50 -5%) to male mature guinea pigs during 60 days. The hormones secretion profile and the lead accumulation were monitored weekly by analyzing the blood samples. Lead exposure does not seem to affect greatly estradiol, progesterone and LH secretion in blood but the correlations in some cases result significantly. Different doses of lead applied show different effects in testosterone secretion. Low dozes increase testosterone concentration in blood (r = 0.78, α = 0.05) while high dozes decrease it (intermediate dose r = -0.83, α = 0.05 and LD 50 -5%, r = -0.87, α = 0.05). The secretion of FSH increases quickly with the application of the highest dose (r = 0.93, α = 0.05). The high secretion of FSH while the testosterone secretion decreases is an indicator of Leydig cells failure confirmed by histological examination of testicules.