Becoming a father can sap you of your energy, your sleep, your income--and, it turns out, your hallmark hormone of maleness: testosterone.
In a study of 465 Filipino men, researchers measured testosterone levels when the men were single in their 20s, then again five years later, when about a third of the men had kids. The researchers found that childless men experienced only a slight, age-related drop in their hormone levels, while fathers saw their levels drop almost twice as much. Those with the least testosterone: dads who were most involved in their children's daily care.
The results suggest that it's...