Paternal care affects sons’ testosterone levels

testosterone

The male sex hormone testosterone. © Evgeny Gromov /iStock

Men who are caring and caring for their children often have lower testosterone levels than those who do not have children or are not very involved in caring for them. A long-term study of almost 1,000 young men now suggests that fathers’ behavior could also have an impact on their sons’ later hormonal balance. According to this, testosterone levels are lower in new fathers if their own father took care of them a lot during their youth. However, according to the results, paternal care in early and middle childhood has no influence.

The sex hormone testosterone has a significant influence on how male individuals engage in reproduction. This can be seen in animals and to some extent in humans as well: men with high testosterone levels typically invest more in courtship, while low testosterone levels favor a man’s nurturing of his offspring. Previous studies have shown that men’s testosterone levels drop when they become fathers and take part in childcare.

Long-term study of the father-son relationship

A team led by Lee Gettler from the University of Notre Dame in Indiana has now researched the influence of a relationship with one’s father on testosterone levels in young men. The researchers interviewed the families of 966 Filipino boys from infancy to adulthood between 1983 and 2014 and measured the testosterone levels of the sons in adulthood using saliva samples. For the evaluation, Gettler and his team analyzed to what extent the presence of the father during early and middle childhood and during adolescence was associated with the later testosterone levels of the sons.

The result: “When the fathers lived with their sons and participated in childcare during adolescence, the sons had lower testosterone levels in adulthood – both before and after becoming parents themselves,” the researchers report. This result was independent of the sons’ own upbringing and partnership behavior, which can also have an influence on the testosterone level. It also played no role in the sons’ testosterone levels whether the father was present during early and middle childhood, i.e. before puberty.

Social influence on testosterone levels

From the researchers’ point of view, the most likely explanation for these effects is that the social relationship with the father during puberty changes the so-called hypothalamus-pituitary axis, which regulates testosterone production. This is largely inactive before puberty and only begins to mature in adolescence. “Our results suggest that adolescence may be a sensitive period in which experiences of nurturing and social relationships, particularly with fathers, may affect testosterone regulation in offspring in adulthood,” the researchers write.

However, the authors did not record the testosterone levels of the fathers of the young men examined. Since the regulation of testosterone production also has a hereditary component, this could be an alternative explanation. “For example, if fathers who are genetically predisposed to have higher testosterone levels dedicate less time to caring for children, their sons could inherit those genes and produce higher testosterone levels themselves — not because of social conditioning, but because of genetic predisposition.” the authors. However, they consider it unlikely that the results could be fully explained by genetic factors: “Such a genetic effect would influence the behavior of fathers at all stages of their children’s development and not only in adolescence.”

Source: Lee Gettler (University of Notre Dame, Indiana, USA) et al., Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2202874119

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