What is testosterone primarily known as in male physiology?

Testosterone is primarily known as the male sex hormone because it plays a crucial role in the development of male reproductive tissues, such as the testes and prostate, as well as promoting secondary sexual characteristics like increased muscle and bone mass, body hair distribution, and voice deepening during puberty. It is essential for maintaining libido and overall male reproductive health throughout adulthood. This hormone is produced mainly in the testes in men and is responsible for many functions that define male physiology, making it a key factor in male sexual differentiation and function.

The other options refer to hormones with different roles in the body: female reproductive hormones are involved in female sexual development and functions, growth hormone focuses on growth and development in both sexes, and thyroid hormones are critical for regulating metabolism. Each of these has distinct roles that do not encompass the primary functions attributed to testosterone.