Public Release: 

Hopkins research shows nature, not nurture, determines gender

Johns Hopkins Medicine

Two Johns Hopkins Children's Center studies confirm that prenatal exposure to normal male hormones alone dictates male gender identity in normal XY male babies, even if they are born without a penis. The results seriously question the current practice of sex-reassigning some of these infants as females, performing castrations or other surgery to align them cosmetically and hormonally with a female role.

In what are believed to be the first studies of their kind, Hopkins researchers followed the development of 27 genetically male children -- with normal XY male chromosomes. All were born with cloacal exstrophy, a rare, major defect characterized by lack of a penis, but presence of normal testicles, indicating exposure to normal male hormone patterns before birth. Twenty-five of the children were reassigned by physicians at birth, castrated and raised as females. Presenting the findings at the Lawson Wilkins Pediatric Endocrine Society Meeting in Boston today, William G. Reiner, M.D., a child and adolescent psychiatrist and urologist at the Hopkins Children's Center, reported that the majority of these children, between the ages of 5 and 16, have subsequently "reassigned" themselves back to males. All 27 showed strong male behaviors, activities and attitudes.

"These studies suggest that male gender identity is directly related to normal male patterns of male hormone exposure in utero," says Reiner. "These children demonstrate that normal male gender identity can develop not only in the absence of the penis, but even after the removal of testicles or castration at birth, and unequivocal rearing as female. Rather than the environment forming these children's gender identity, their identity and gender role seem to have developed despite a total environment telling them they were female."

In the first study, Reiner and Director of Pediatric Urology at the Hopkins Children's Center John Gearhart, M.D., followed 14 children whose testicles and male hormone levels in utero had been normal at birth. All but two had been surgically reconstructed as females and raised unequivocally as females. Today, the 12 raised as females are strongly male-typical in their activities, attitudes, friends, and play. Six of them reassigned themselves back to their male gender, at ages 5, 7, 8, 9, 11, and 12 years old. The two who were not reassigned female at birth were developmentally far more like their normal male peers and psychologically better adjusted than the sex-reassigned children, Reiner reports.

In the second study, Reiner followed an additional 12 genetically male children in his Child and Adolescent Psychiatry Clinic for Gender Identity and Psychosexual Disorders, in the Johns Hopkins Children's Center. Referred from outside university centers, all had been born with this same pelvic field defect, and sex-reassigned as females at birth. Eight of the 12 have since sex-reassigned themselves back to male. Three sets of parents plan to tell their children their genetic sex of birth "soon"; all expect their children to switch back to a male gender when they learn their birth gender.

Reiner called for a thorough reexamination of the practice of sex-reassignment of children, and urged extreme caution in surgically reconstructing these children at birth. "These studies indicate that with time and age, children may well know what their gender is, regardless of any and all information and child-rearing to the contrary. They seem to be quite capable of telling us who they are, and we can observe how they act and function even before they can tell us."

He urges parents to get all the data before making surgical or gender decisions. "Children with major, severe genital anomalies -- not necessarily hypospadias or other common anomalies -- but those with severe genital problems need early and full consultation at a medical center where such children are routinely evaluated and followed long-term, and where outcomes are thoroughly studied."


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