Testosterone Levels in Men Drop as They Become Fathers

Low testosterone suppresses the aggressive traits of men to allow them to become caring fathers Lack of testosterone in men may be associated with effeminate behavior and overall sissiness, but scientists have uncovered what may be a shocking new truth about male hormones. As it turns out, low testosterone is a natural part of the male life cycle. And the most virile of men are the ones who lose the most.

These findings were presented as the result of a recent study, published in the Proceedings of the National Academy of Sciences on September 12. Six hundred and twenty-four Filipino men participated in the study which lasted over a period of four and a half years. Their testosterone levels were measured using saliva samples both at the beginning and the end of the study period, in both the morning and in the evening.

The research showed that men with high morning levels of the hormone to begin with were more likely to become fathers by the end of the study. But the study also showed that in becoming a father a man’s testosterone levels were on average 26% lower in the morning and 34% lower in the evening compared to his own levels before he became a dad. Normal aging would only produce a 14% drop.

Additionally, men who spent three or more hours per day taking care of their child experienced greater drops in testosterone than the men who were less involved in raising their children. In other words, mere awareness of being a father is not the only cause for the testosterone drop – interaction with one’s child plays a part as well. The greatest drops in testosterone occurred when the child was an infant. Fathers of newborns experienced a median testosterone drop of 50%, which endured until the child was a toddler.

This occurred regardless of the man’s original testosterone level. The study author Lee Gettler, an anthropology PhD candidate at Northwestern University urged that there is an important distinction to be made here. “We did not find that fathers with the lowest testosterone were simply inclined to become caregivers.”

This makes sense since testosterone is closely linked with traits such as strength, aggression and virility, which are important in survival, both purely physical and genetic. Men with high testosterone levels might have a competitive edge in, still evolutionarily primitive, human mating habits. But that is where the competitive edge stops. Aggression and risk-taking are not desirable qualities in a father, so testosterone drops. This has been observed in several species where the males care for their offspring.

So when you notice the men around you mellowing as they become fathers, now you know, it’s simply a matter of hormones.