June 27, 2001 A published study of hormonal changes in a group of Canadian men becoming fathers for the first time showed a decrease in testosterone and cortisol levels and a higher level of estradiol concentrations, a hormone known to influence maternal behavior.
The study, which appears in the June issue of Mayo Clinic Proceedings, says the findings are worthy of further study, but they don’t say what, if any, physiologic relevance of the hormone changes is known.
Volunteer study subjects were recruited from first-trimester prenatal classes in Kingston, Ontario, Canada, in February 1999. As part of the study, 23 dads provided saliva samples from recruitment through three months after the birth of their children. Researchers also recruited 14 men who were not fathers from the general population to serve as age-matched controls for seasons and time of day. Estradiol, testosterone and cortisol levels were quantified.
Authors of the study are Sandra J. Berg, M.Sc., and Katherine E. Wynne-Edwards, Ph.D., of the Department of Biology at Queen’s University in Kingston, Ontario, Canada.
"Relative to control subjects, expectant fathers have lower testosterone and cortisol concentrations and more frequently detectable estradiol," says Dr. Wynne-Edwards. "These results confirm and expand on the results of the only previous study, suggesting that men’s hormones change as they become fathers."
The study’s findings included:
* The testosterone concentration was significantly lower in the overall sample of 23 dads than in the 14 control subjects
* Cortisol concentration was significantly lower in dads than in the control group.
* Dads had a higher proportion of samples with detectable estradiol concentrations.
The finding that estradiol was detected in a larger proportion of samples from dads than from controls is novel, the authors write. Men becoming fathers were exposed to more estradiol than control men, and that exposure increased after the birth of their child. Estradiol is an important hormonal component of mammalian maternal behavior in women, non-human primates and other mammals, but no animal research has yet described estradiol changes in naturally paternal male mammals.
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