The hypothalamic-pituitary-gonadal (HPG) axis represents a complex interplay in which male reproductive and sexual functions are regulated.The role of estrogen,once relegated to being that of a minor player,has had its importance resurrected by a recent research.rnWith regards to male fertility,Clomiphene citrate and tamoxifen are selective estrogen receptor modulators and the medications most frequently used in the management of male fertility and hypogonadism.Usage of Clomiphene results in a concomitant rise in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) at the level of the pituitary,resulting in an increase in intratesticular and serum testosterone levels and theoretically creating a more favorable environment for sperm production within the testis.Aromatase inhibitors,such as Arimidex,are primarily used in patients with a testosterone to estradiol ratio ＜ 10∶1 to increase testosterone production and spermatogenesis.Targeting estradiol levels has also been shown to have clinical value when optimizing sperm retrieval rates in men with nonobstructive azoospermia.1