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Testosterone Levels Fall in New Dads

Mother Nature Helps Guys Become Dads
by Mommy MD Guide Rallie McAllister, MD, MPH

More proof that Mother Nature really is a girl: The results of a new study* show that male testosterone levels fall after the birth of their offspring. Guys might not be thrilled to know this, but it’s all good. Researchers claim that the drop in the juice helps ensure that males will help new moms care for those demanding little newborns.

They say that testosterone levels fall after the birth of offspring in males of other species that help their mates care for their young. As you’ve experienced, testosterone boosts chest-thumping behaviors and physical traits that help males compete for a mate. After higher levels of testosterone help the guy get the girl, those “mating-related” activities can conflict with the responsibilities of fatherhood. This makes it advantageous for the male body to reduce production of testosterone. At least that’s how Mother Nature sees it.

Unlike other mammals, humans are unusual in that our offspring depend upon their parents for feeding and protection for more than a decade after birth. That’s one thing that separates a guy from say, a tom cat or a wild boar. Raising human children is such a mammoth effort that it requires two parents, and the results of this study show that this is why Mother Nature has taken it upon herself to biologically wire guys’ bodies and brains to help him get the job done.

The new study followed more than 600 men who were not fathers and checked their testosterone levels before and after they became dads. The researchers found that men who started with high testosterone were more likely to become fathers, but once they did, their testosterone took a hard nosedive. Ouch! Their findings suggest that this testosterone levels fell consistently in guys who become the most involved with their kids’ child care responsibilities. That’s just one more hazard of changing diapers and doing those middle-of-the-night bottle runs.

The new study’s findings suggest that fathers seem to experience an especially large, (but thank God, temporary), decline in testosterone when they first bring home their newborn babies. Since fatherhood and the demands of taking care of the kid require some serious emotional, psychological and physical adjustments, lower testosterone levels help a guy meet those demands.

New dads can take comfort in knowing that the hormonal changes are only temporary. And here’s another consolation prize: Having periods of low testosterone levels may help protect guys from a few diseases as they age, including prostate cancer. Periods of low testosterone levels following the birth of a new baby may help explain why single guys often have worse health than married men and fathers. It’s not just because they’re eating too many burgers, drinking too much beer, or having too much fun.

*Lee T. Gettler, Thomas W. Mcdade, Alan B. Feranil, Christopher W. Kuzawa. Longitudinal evidence that fatherhood decreases testosterone in human males. Proceedings of the National Academy of Sciences, 2011; DOI


The information on MommyMDGuides.com is not intended to replace the diagnosis, treatment, and services of a physician. Always consult your physician or child care expert if you have any questions concerning your family's health. For severe or life-threatening conditions, seek immediate medical attention.