The Effect of Aromatase on the Reproductive Function of Obese Males

Obesity has increased dramatically worldwide, which is associated with male infertility. Androgen deficiency, impaired spermatogenesis, and erectile dysfunction are characteristics of male infertility. The balance of androgens and estrogens is essential for maintaining normal reproductive function in males. Aromatase, the rate-limiting enzyme in the conversion of androgens into estrogens, is present in various tissues. The expression of aromatase is proportional to body fat mass and causes more fat accumulation, thus forming a vicious cycle. Excessive aromatase activity in adipose tissue leads to increased conversion of androgens into estrogens, eventually results in a reduction of testosterone levels and is the underlying reason for obesity-related infertility. In the male reproductive system, all testicular somatic cells and germ cells express aromatase, except for peritubular myoid cells. The results of studies regarding the effect of aromatase in testicular somatic cells and germ cells have been contradictory. The effect of estrogens in testicular somatic cells is inhibitory, leading to reduced testosterone levels and sperm production; however, it has been observed that aromatase participates in the acquisition of sperm motility. The overall effect of estrogen modulation is an inhibition of spermatogenesis. Aromatase inhibitors are an effective therapy for obesity-associated hypogonadism because they restore normal sex hormone levels and improve semen parameters. This article systematically introduces the basic knowledge of aromatase and provides information of the current advances relating to aromatase in male reproductive function. Increasing our knowledge on the role of aromatase in male obesity could help in proposing new approaches to treat infertile men.