Changes in testosterone, cortisol, and estradiol levels in men becoming fathers

To quantify longitudinally steroid hormone (testosterone, cortisol, and estradiol) concentrations in men becoming fathers for the first time ("dads").

Volunteer study subjects were recruited from first-trimester prenatal classes in Kingston, Ontario, in February 1999. Twenty-three dads provided saliva samples from recruitment through 3 months after the birth of their children. Fourteen men who were not fathers were recruited from the general population to serve as age-matched controls for season and time of day. Estradiol, testosterone, and cortisol levels were quantified.

After controlling for effects of time of day and season, dads had lower mean +/- SE testosterone (6.5+/-0.7 vs 10.0+/-0.9 ng/dL; P<.005) and cortisol (morning values, 0.30+/-0.05 vs 0.53+/-0.05 microg/dL; P<.005) concentrations, a higher proportion of samples with detectable estradiol concentrations (68% [308/454] vs 57% [87/154]; P=.01), and higher estradiol concentrations in those detectable samples (3.81+/-0.09 pg/mL [13 dads] vs 3.26+/-0.11 pg/mL [9 controls]; P<.002) than did control men. Within 10 individual dads with frequent samples before and after the birth, the percentage of samples with detectable estradiol was lower during the month before the birth than during the month after (51% vs 71%; P=.02), and cortisol concentration was increased in the week before the birth (to a mean of 0.16 microg/dL). In each of 13 dads providing frequent samples, testosterone concentration and variance were low immediately after the birth (no change from previous levels in 5, decrease after prebirth increase in 3, and decrease relative to all other times in 5).

In this population of Canadian volunteers attending prenatal classes, expectant fathers had lower testosterone and cortisol levels and a higher proportion of samples with detectable estradiol concentrations than control subjects. Individual patterns of testosterone variance relative to the birth and estradiol and cortisol concentrations immediately before the birth may be worthy of further investigation. The physiologic importance of these hormonal changes, if any, is not known. However, they are hormones known to influence maternal behavior.