Testosterone

Testosterone is the primary male sex hormone and androgen in males. In humans, testosterone plays a key role in the development of male reproductive tissues such as testicles and prostate, as well as promoting secondary sexual characteristics such as increased muscle and bone mass, and the growth of body hair. It is associated with increased aggression, sex drive, dominance, courtship display, and a wide range of behavioral characteristics. In addition, testosterone in both sexes is involved in health and well-being, where it has a significant effect on overall mood, cognition, social and sexu

The libido or sex drive ( ; , "lust, desire") refers to a psychological energy that, in common parlance, encompasses all forms of sexual desire, but is sometimes also regarded as the driving force behind other needs, such as a mother's love for her infant. The term was originally developed by the Austrian neurologist Sigmund Freud, the pioneer of psychoanalysis. Initially it referred only to specific sexual needs, but he later expanded the concept to a universal desire, with the id being its "great reservoir". As driving energy behind all life processes, libido became the source of the social

rare condition in older men, characterized by measurably low testosterone levels

deepening of the voice of people as they reach puberty

medication and naturally occurring steroid hormone