Therapeutic Effect of Aromatase Inhibitor in Two Azoospermic Dogs with High Plasma Estradiol-17β Levels

Two azoospermic dogs with high plasma estradiol-17 β (E2) levels were subcutaneously injected with an aromatase inhibitor (AI), 4-androstene-4-ol-3,17-dione, 2 mg every other day for 4 weeks. Before the AI treatment the plasma E2 levels of the two dogs (21 and 22 pg/ml, respectively) were higher than those of 2 normal dogs (8.1 and 12.3 pg/ml), and they fell to 11-17 pg/ml between 1 and 4 weeks after the start of AI treatment. The plasma testosterone levels after the start of AI treatment had increased to 2.1-3.1 ng/ml. A small number of sperm were detected in the semen of the two dogs between 3 and 6 weeks after the start of AI treatment. These results indicate that the testicular function of infertile dogs with high plasma E2 levels can be temporarily improved by AI therapy.