Biopsychosocial Determinants of Gender.

Biopsychosocial Determinants of Gender, Heino F. L. Meyer-Bahlburg, Columbia University

One of the major issues in the ongoing controversy about the psychosocial management of intersex newborns is gender assignment. A resolution of the controversy requires a better understanding of the development of gender-related behavior and identity and its various determinants: genetic, hormonal, and psychosocial. I focused on the most prevalent intersex syndrome, classical (prenatal-onset) congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, and summarized recent psychological research in children and adults with this syndrome, complemented by studies on intersex syndromes in 46, XY individuals. The accumulated evidence to date permits the following preliminary conclusions: (a) A contrast of girls with CAH to girls with diabetes mellitus shows that the behavioral masculinization seen in girls and women with classical CAH cannot be explained by the fact that CAH is a chronic disease. (b) Various studies of parental attitudes and behavior have failed to account for the behavioral masculinization of CAH girls by parental socialization. (c) Comparison of both prenatal androgen excess in 46,XX individuals and prenatal androgen deficiency in 46,XY individuals to control conditions point to androgens as the primary determinant of gender-related behavior. By contrast, prenatal estrogen deficiency seems to be unrelated to behavioral gender differentiation. (d) The decisive role of prenatal androgen is further underlined by dose-response analog studies in CAH children and adults as well as the effects of prenatal suppression of androgen excess in CAH children. (e) When predicting gender-related behavior of CAH girls and women from the degree of CAH-syndrome severity (which indicates the degree of androgen excess), the addition of the molecular genotype of the defective 21-hydroxylasen gene to the equation does not improve the prediction. (f) No human evidence exists to date for a role of the neonatal androgen surge in the development of gender-related behavior. (g) While the evidence for prenatal androgens as the primary determinant of gender-related behavior is very strong, gender identity does not seem to be directly affected. Overall, the conclusions raise the question how the status of the androgenization of the brain at birth can be used for a prognosis of gender-identity outcome and guide gender assignment decisions. In the absence of reliable techniques of brain imaging of the newborn for this purpose, many have argued for using masculinization of the genitals as an indicator of brain masculinization. However, this approach encounters a variety of significant problems, applies at best only to selected syndromes, has only very modest predictive power for gender-related behavior, and is very problematic in the prediction of gender identity.