Testosterone 'drops' in new fathers: study
13 September 2011 Last updated at 12:32 BST
A new study has found that the level of the hormone testosterone in a man drops when he becomes a father.
The research was conducted by a team in the US and has been published in the journal Proceedings of the National Academy of Sciences.
The researchers found a significant drop in testosterone levels when men first became fathers, and believe this may encourage nurturing.
Christopher Kuzawa of Northwestern University, who worked on the study, told BBC World Service, that this is good news for men, as lower testosterone levels are associated with many health benefits.