Fascinatingly, testosterone (and estrogen, for that matter) is technically a steroid hormone. Even more interestingly, it is synthesized from cholesterol, which is also a steroid. Many Americans view both cholesterol and steroids with a skeptical eye, as if they were dangerous substances. However, biologically, steroids are simply microscopic molecules with a specific structure made of 4 fused rings and various side chains. And cholesterol is a crucial molecule to human and animal cells, which only becomes a problem when a too-high amount of it in the blood contributes to artery buildup.