As men age, their testosterone levels gradually decrease. this may cause a reduction in lean body mass, an increase in fat, and other undesirable changes. do testosterone supplements reverse some of these effects? a study in the netherlands assigned 237 men aged 60 to 80 with low or low-normal testosterone levels to either a testosterone supplement or a placebo. the report in the journal of the american medical association described the study as a "double-blind, randomized, placebo-controlled trial." explain each of these terms to someone who knows no statistics.