Research confirms impact of fatherhood on men's hormones

Friday Sep 16, 2011

A study of young Filipino men provides conclusive evidence that becoming a father and, perhaps even more significantly, involvement in infant care, lowers men's levels of testosterone. Previous Canadian research has suggested that fatherhood can affect men's levels of several hormones, specifically: increases in cortisol and prolactin in men near the end of their partners' pregnancies (Storey 2000), decreases in testosterone and cortisol when fathers' babies were 3 months old (Berg, 2001) and increases in prolactin in response to hearing a baby's cry (Fleming 2002).

What is significant about the new study, led by anthropologist Lee Gettler, a doctoral candidate at Northwestern University, and published in the Proceedings of the National Academy of Sciences, is that it followed a group of young men for 4.5 years. That made it possible to compare hormone levels in men before and after they became fathers. This eliminates the possibility that men with lower levels of testosterone are more likely to become fathers in the first place. In fact, in Gettler's study, men with higher levels of testosterone were more likely than men with less testosterone to become partnered fathers over the study period.

The men who had become partnered fathers by the 4.5 year follow-up experienced a large decline in testosterone levels, while non-fathers experienced a modest decline. Moreover, fathers who were highly involved in infant care had lower levels of testosterone than fathers who were not involved in infant care. "Our findings suggest that human males have an evolved neuroendocrine architecture that is responsive to committed parenting," the authors wrote. Another way to put it is that male biology is designed to support involved fathering and that the relationship between fatherhood and hormonal changes is bidirectional. Hormonal changes not only help to biologically prime men to become involved in the care of children but also responds to support their caregiving activity. This study was widely discussed, and to some extent, misunderstood in popular media. The read the study authors' blog about what they feel their study really showed, click here.

Read the abstract of the journal article Longitudinal evidence that fatherhood decreases testosterone in human males.

Read the text of On Testosterone and Real Men, an Interview with Lee Gettler.