Androgen replacement therapy (ART) in males with low levels of testosterone due to disease or aging. It is a hormone treatment often prescribed to counter the effects of male hypogonadism[2] or who for men who have lost their testicular function to disease, cancer, or other causes.[3] It is sometimes used for late-onset hypogonadism (so-called "andropause"), but the significance of a decrease in testosterone levels is debated and its treatment with replacement is controversial. The Food and Drug Administration (FDA) stated in 2015 that neither the benefits nor the safety of testosterone have been established in older men with low testosterone levels.[4] Transgender hormone therapy for transgender people introduces hormones associated with the gender that the patient identifies with (notably testosterone for transgender men and estrogen for transgender women).