Declining physical activity and mental alertness in the aging male: reduced efficiency, easy fatigability, lack of concentration, weak memory, disturbances of libido and potency, irritability, disturbances of sleep, depressive moods, and general vegetative complaints often attributed to androgen-deficiency are often overcome or improved with Mesterolone 25 use. Potency Disturbances: Mesterolone overcomes androgen-deficiency linked potency disturbances and may provide improvement in cases of potency disturbance which are not androgen-deficiency linked. Hypogonadism: Function and growth of androgen- dependent tissues are stimulated by Mesterolone. It may be used for androgen replacement therapy after puberty. Reduction of Sex hormone- binding globulin (SHBG) increasing free testosterone levelsoem Infertility: Treatment of oligozoospermia and insufficient Leydig-cell secretion linked infertility. Treatment can increase sperm count, quality, and fructose concentration increasing chances of fertilization.