Abstract:We report a case of myelodysplastic syndrome (MDS) treated effectively with testosterone enanthate. A 70-year-old man was diagnosed with low-risk MDS in 1998, and he was first given methenolone acetate orally because of gradual progression of anemia and thrombocytopenia. However, this treatment was not effective, so we changed the treatment to testosterone enanthate because of his symptoms with late-onset hypogonadism. Three months after testosterone replacement therapy (TRT), anemia and thrombocytopenia had improved , and mean platelet count and hemoglobin had significant increases from 2.36 Ϯ 0.45 ¥ 10 4 to 3.83 Ϯ 0.78 ¥ 10 4 /mL, and from 11.7 Ϯ 0.81 to 15.2 Ϯ 1.00 g/ dL, respectively, which contributed to a decrease in platelet transfusion requirement. Since then, the patient has been on a good clinical course. The present case suggests that testosterone enanthate administration could be an alternative treatment for men with MDS, even in the case where treatment with anabolic-androgenic steroids is not successful, and suggests another interesting effect of TRT on platelets.