To our knowledge, the action of estradiol which is produced from testosterone by aromatase on human spermatogenesis has not been fully clarified. In oligozoospermia, with high values of E₂/T ratio, it is considered that the role of estradiol is suppressive to spermatogenesis. In this study, alteration of spermatogenesis was evaluated when serum estradiol levels were decreased by suppression of aromatase activity.
Nine male infertile patients were treated with testolactone (Teslac^®: 1.0g/day, for 3 months), one of the aromatase inhibitors. Four of them had an increase in sperm count (more than 10×10⁶/ml relative to base line).
In endocrinological findings, serum estradiol levels and E₂/free T ratio were significantly decreased after treatment. Serum free testosterone levels were significantly increased in all cases, presumably from decreased sex hormone binding globulin (SHBG) levels. These findings suggested the effectiveness of the administrated aromatase inhibitor. In particular four patients whose sperm counts were improved after testolactone treatment had high values of basal serum estradiol levels and E₂/free T ratio before treatment, and these values were normalized after treatment.
In conclusion we suggest that an aromatase inhibitor may be effective to male infertile patients with high serum estradiol levels.