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DENVER — Fatherhood marks a wonderful time in a man’s life.  Yet it’s also a time when testosterone — that most male of hormones — takes a dive.

Experts say the reason is because men’s bodies evolved hormonal systems that helped them commit to their families once children were born. It also suggests that men’s behavior can influence hormonal signals in their bodies, and not the other way around.

The largest study of its kind looked at 600 men first then they were 21 and then five years later. It found fathers had more than double the amount of testosterone drop than childless men.

Men who spent more than three hours a day caring for children had the lowest testosterone.

The study is welcome news to moms.

“I think being at home is just as difficult and I think it’s important to have support,” said Denver mom Julie Boone.

Proud father Andrew Southwell said the idea of a dip in testosterone doesn’t bother him at all.

“I’m pretty confident in my own skin,  have my own business have two boys so there’s going to be plenty of testosterone flowing through the house here,” Southwell said.

Researchers say the study also suggests lower testosterone is nature’s way of enforcing families. Lower testosterone can make a man less likely to to look other mates.

Lower testosterone may also bring out better communication skills in men.

Researchers say men shouldn’t fear the dip in testosterone.  It does not affect a dad’s masculinity.

Peter Ellison, a professor of human evolutionary biology, told the New York Times, “I think American males have been brainwashed” to believe lower testosterone means that “maybe you’re a wimp, that it’s because you’re not really a man.”

While this seems to be a positive effect of a hormonal change,  doctors warn that a serious drop in testosterone can be brought on by other factors and trigger serious health problems.

While a drop in testosterone is expected for men who become fathers, doctors warn too much of a loss can be harmful.

Dr. Margaret Wierman, professor in medicine physiology and biophysics at the University of Colorado, said medications can cause problems

“If you’re taking a lot of pain pills, it’ll block your testosterone, or lastly if you take high dose steroids,” Wierman said.

The symptoms of  an unhealthy drop in testosterone include fatigue, loss of muscle mass, failure to achieve an erection and  a loss of sex drive.  Any man with these symptoms should seek medical attention.

You can read more on maintaining a healthy  testosterone level at