Castrated men tend to live much longer than fully endowed guys, according to a new study that suggests male sex hormones are responsible for shortening the lives of men.
The findings, published today in the journal Current Biology, could offer clues on how to extend the male lifespan. There might be a tradeoff of quantity versus quality, though.
The possible negative consequences of castration include "decreased libido, depression and loss of physical strength," according to coauthor Kyung-Jin Min of Inha University.
For the study, Min and colleague Cheol-Koo Lee, an associate professor in the College of Life Sciences and Biotechnology at Korea University, analyzed genealogy records of noble members of the Imperial court of the Korean Chosun dynasty (A.D. 1392-1910).
The castrated boys either lost their reproductive organs in accidents (such as after being bitten by a dog) or they underwent castration purposefully to gain access to the palace. Male rulers, in particular, felt they could trust eunuchs with their female family members and harems, if they had them. Eunuchs could marry, though, and often adopted children, including other castrated boys.
The researchers found that the eunuchs lived 14 to 19 years longer than other men did. Three even lived to 100 or more, a feat of longevity that remains relatively rare among men even today.
The effect wasn't just due to fine palace living either, since kings and other male members of the court had the shortest lifespans of all. The eunuchs also spent time both inside the palace and out.
"Since castration extends lifespan by reducing male sex hormones, we still believe that the effect would be the same today," Min told Discovery News. "In fact, castration was also performed in the early 1900s in a Kansas mental hospital. Castrated patients lived 13 years longer than intact patients, which is similar to (the results) of our study."
Min continued, "Testosterone is known to increase the incidence of coronary heart disease and reduce immune function in males."
Lee added that because of this immune function suppression, eunuchs could be better able to resist infections.
The longevity differences between eunuchs and other men could also relate to lifestyle.
Lee explained that castrated men tend to be less violent, and additionally may avoid physically dangerous situations that could put them at risk.
The researchers next plan to examine the lifespan of eunuchs in other cultures, such as the Chinese and Ottoman empires, to see if the latest conclusions carry over to those individuals.
In the meantime, few expect young men to willingly undergo castration in order to have lengthier lives. Younger people now, however, are often interested in restricting their calorie intake, which can achieve similar benefits.
Lee's lab is currently investigating how calorie restriction may modulate gene expression, leading to possibly reduced testosterone levels.