Typically, eunuchs are men that have been castrated early enough in their lives to force hormonal changes which would cause a lack of testosterone. In ancient times, men were castrated against their will so that they could perform a specific task where testosterone could present a definite problem—like being in charge of a harem, for instance!
There is still a surprising amount of eunuchs around today. There are about 2 million eunuchs in India, referred to as hirja. They are transsexual individuals who have had surgical castration surgery instead of gender re-assignment surgery.
Advanced prostate cancer patients are commonly castrated. About 80,000 of these men will be chemically castrated in the US each year. Because of the increased life expectancy after castration, there are about half a million chemically-castrated eunuchs in the United States at any given time.
Many of these men do not like the term "eunuch," although they meet all physiological characteristics of post-pubertal eunuchs. Some of them embrace the term because it has historical meaning and, psychologically, it grounds them.
Eunuchs do have at least one big advantage: They live 13.5 years longer than non-castrated males because of their lack of testosterone. Testosterone suppresses the natural immune system and therefore has a negative effect on an individual's health.
