Testosterone is often described as the male sex hormone. Women also produce testosterone, but in much smaller amounts. Aside from its sexual effects such as stimulating beard growth and deeper voices, testosterone is an important anabolic hormone that has a significant impact on the energetic costs in men. That is, it promotes anabolism, or muscle-building, and increases metabolism, the rate at which that muscle burns calories. Testosterone also promotes the burning of fat tissue. And yes, it can also boost libido and mood.