What is the primary role of testosterone?

The primary role of testosterone is to support the development of male characteristics. This hormone is crucial in the development of male reproductive tissues such as the testes and prostate, and it promotes secondary sexual characteristics that are typically associated with males, including increased muscle mass, bone density, and body hair growth. Testosterone is also important in spermatogenesis and influences behaviors that align with male reproductive strategies.

The other options, while relevant to various physiological processes, are not primarily associated with testosterone. For example, stimulating uterine contractions is more related to hormones such as oxytocin. Regulating metabolism involves other hormones like insulin and glucagon, while sleep quality is influenced by hormones like melatonin and cortisol rather than testosterone. Thus, the selection of testosterone's role in developing male characteristics accurately captures its most significant function in the body.