Fatherhood Lowers Testosterone Level, says Study

Women may be considered as the primary caregivers of children, but a study on fathers from Cebu, Philippines shows that men’s testosterone level dips once they become fathers, shifting them into ‘daddy mode’.

Says researcher Lee Gettler of Northwestern University in Chicago, Illinois, "Men are, to a certain degree, hardwired to take care of their kids. This is important because traditional models of human evolution have portrayed women as the gatherers that take care of the kids and stay behind."

Researchers explain that such an occurrence can explain what happens when the testosterone levels are high, on the other hand. High testosterone makes men more inclined to get involved in non-fatherly qualities, such as competing for a mate and other activities.

According to the study, those who had the biggest decline in testosterone were those who just had newborns.

465 men took part in the Cebu Longitudinal Health and Nutrition Survey back in 2005 when they were still 21.5 years old. Their testosterone levels were studied twice, once before they woke up and another when they are sleep. These measurements were then repeated four years after, at 29 years old, when around 50 percent of them were already dads.

Here are the results:
•    Men who stayed single had a 12 to 15 percent decline in testosterone.
•    New fathers, those with a baby between 1 month and 1 year old, had a 30 percent decline in testosterone.
•    Fathers of newborns had as much testosterone as 5 times that of single men and twice that of fathers of older kids.

 

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Says Gettler. "Newborn babies bring about really intense physical, emotional and psychological changes. We kind of see men's biology responding to that, in line with what we would expect in men who are trying to transition into this new role of being a father to a newborn."

As to the effects, the researchers believe there will be probable repercussions on the men’s libido and muscle mass, but these will most likely be mild in nature.

The researchers believe that lowered testosterone may urge men to spend more time at home with the family, given the decline in the need to go out and mate.

Adds Gettler, "When fathers make this choice - this active decision to be involved - testosterone levels react by going down even further. Their bodies respond by saying, 'This is where we are focused now, we are focused on the kids.'"

This might also be the reason why having a spouse and fathering children become beneficial to a man’s health.

Says a senior lecturer in andrology at the University of Sheffield, testosterone levels in men generally don't change that much. They can slowly decline as men get older and change in response to some medical conditions and treatment, but to see dramatic changes in response to family life is intriguing.
"The observations could make some evolutionary sense if we accept the idea that men with lower testosterone levels are more likely to be monogamous with their partner and care for children. However, it would be important to check that link between testosterone levels and behavior before we could be certain."


Sources:
•    September 12, 2011. Jennifer Welsh. “Fatherhood Lowers ‘Manly’ Hormone, Keeps Dad at Home” livescience.com
•    September 12, 2011. Michelle Roberts. “Fatherhood ‘lowers testosterone to keep men loyal’” bbc.co.uk


Photo by freeflight1046 via flickr creative commons