Low testosterone can impact everyone: men, women, older individuals, and young children.
However, due to the large volume of testosterone in men and the increasingly significant role it plays in their functioning, this gender is the one most likely to become impacted by lowered hormone levels. Decreased testosterone levels are also likely to cause a larger range of issues in males than in women as their age declines.
Outside of gender, it becomes difficult to scientifically determine which demographic receives the highest incidence of lowered testosterone. Older males are an obvious choice, as all males must deal with declining testosterone in the way that all females must deal with menopause. However, this does not account for the individuals that were already born with the condition. And if an individual possessed low hormone levels in their youth, does this truly qualify them for the elderly demographic?
Regardless, low testosterone levels can happen to men of virtually any age. Men who sustained injury to the genitals are at risk for low testosterone, as are men with autoimmune diseases and those exposed to certain infections. Low testosterone seems to be the result of both natural and external factors, impacting men of all walks of life.
Those born with certain deficiencies or illnesses are impacted by low hormone levels throughout their whole lives. However, this can be lucky. Those who learn about their condition sooner have more time to correct the issue medically, remaining stable in testosterone levels even into old age.