Study finds early exposure to testosterone predicts gender-role behaviors in boys

Low exposure to gonadal hormones during early gestation and infancy predicts higher recalled childhood gender nonconformity in men, according to new research published in Psychological Science. The findings provide evidence androgens such as testosterone play a role in the development of male-typical gender role behaviors in childhood.

“Biological sex is probably the most important factor explaining variability among people, and many diseases — including mental disorders such as depression, anxiety, Alzheimer’s disease, substance abuse, schizophrenia, autism spectrum disorder, and attention deficit hyperactivity disorder — differ by sex in prevalence and/or severity. Understanding the development of psychological sex differences is therefore critical to understanding individual differences in mental health,” said study author David A. Puts, an associate professor and principal investigator of the Behavioral Endocrinology and Evolution Lab at the Pennsylvania State University.

“Research in laboratory animals shows that behavioral sex differences depend heavily on the effects of testosterone on gene expression in the developing brain. However, in people, it is also likely that many behavioral sex differences depend on socialization as boys or girls. We wanted to test whether gender socialization is the only cause of human behavioral sex differences, or whether testosterone might influence the development of the brain more directly, as it does in other mammals.”

For their study, the researchers recruited a sample of 65 men with idiopathic hypogonadotropic hypogonadism (also known as isolated gonadotropin-releasing hormone deficiency), a rare endocrine disorder affecting approximately 1 in 130,000 live births.

“Men with IHH were unambiguously male at birth and raised as boys, almost always without their condition being known until the typical time of puberty,” Puts told PsyPost. “However, they were exposed to low-to-no testosterone from around the second trimester of gestation until they started hormone replacement therapy, usually around the age of 19. Working with people with IHH allowed us to disentangle the direct effects of testosterone on brain development from the role of gender socialization by comparing men with IHH to those without IHH. The two groups were raised as the same gender but differed dramatically in their early exposure to testosterone.”

The men with IHH, along with 32 women with IHH, 463 typically-developing men, and 1,207 typically-developing women, completed a childhood gender nonconformity questionnaire in which they were asked about their peer preferences, toy preferences, dress-up play, fantasy play, and career aspirations as youth.

The researchers found that men with IHH tended to have less stereotypically masculine childhood behaviors compared to typically-developing men. In other words, men with IHH were more likely to recall preferring girls as playmates, experimenting with makeup and jewelry, wearing girls’ or women’s clothing when playing “dress up,” feeling less masculine than their peers, and not feeling good about being a boy. This was particularly true among men who also reported undescended tests at birth, a marker of low perinatal androgens.

“We found that men with IHH reported less childhood gender-role conformity than typically-developing men, suggesting that some of the variation in childhood gender-role behavior is due to the direct effects of testosterone on patterns of gene expression in the developing brain, ” Puts told PsyPost.

In contrast to men, women with a physician-confirmed IHH diagnosis did not differ from typically-developing women in recalled childhood gender nonconformity. Puts and his colleagues also noted that the recalled childhood behaviors of men with IHH were more similar to typically-developing men than to women, indicating that while hormone exposure plays an important role in behavior, it does not tell the entire story.

“The average person should see this not as evidence against a role of gender socialization but as evidence for the additional influence of sex hormones such as testosterone acting directly on the developing brain,” Puts explained. “People who were exposed to different levels of testosterone during their early development are likely to differ in their psychology and behavior even if they are socialized in the same way.”

The findings are in line with experimental animal studies, which have found that exposure to androgens masculinizes the brain and behavior.

“We should also be encouraged that the many thousands of hours and millions of dollars spent on research investigating the influence of sex hormones on the brains and behavior of experimental animals have not been spent in vain,” Puts said. “There are important similarities that can help us understand how our own brains and behavior develop.”

But the study, like all research, includes some caveats.

“From a strictly scientific perspective, the greatest limitation of this study was that it was not experimental,” Puts explained. “Participants were, for obvious ethical reasons, not randomly assigned to groups and then treated with or deprived of testosterone. So it is possible, for example, that men with IHH recall their childhood gender role behaviors differently from men without IHH because they are aware of their condition. We suspect that the tendency would be to recall a childhood that was more, rather than less, gender conforming, and thus that the differences may actually be larger than we were able to measure, but we cannot know this.”

The study, “Low Perinatal Androgens Predict Recalled Childhood Gender Nonconformity in Men“, was authored by Talia N. Shirazi, Heather Self, Kevin A. Rosenfield, Khytam Dawood, Lisa LM Welling, Rodrigo Cárdenas, J. Michael Bailey, Ravikumar Balasubramanian, Angela Delaney, S. Marc Breedlove, and David A. Puts.

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