Materials and Methods: In this experimental study, 40 male Wistar rats with the average weight of 200-250 g and age of 8-10 weeks, divided into 5 groups. Group 1, which called control group, received no treatment. Group 2 received normal saline and Groups 3-5 received extract at a dose of 50, 100 and 200 mg/kg/day of the olive leaves extract (1 cc), respectively. Before the administration of the first gavage and 24 h after that of the last one (i.e., in the 49th day), all the rats were weighed, and blood samples were taken from their tail vein. The blood samples were then centrifuged at 1500 rpm for 20 min, then serum was separated and stored at −80 °C for the measurement of estradiol and testosterone, using immunoassay technique.

Results: The results show a significant decrease in testosterone and estradiol level among the five groups, which is dependent on the concentration of the extract; the decrease in testosterone and estradiol is positively correlated to the concentration of the extract.

Conclusion: In conclusion, olive leaves extract significantly decreased fertility parameters in the male adult rat dose-dependently.