Click-Evoked Otoacoustic Emissions in Children and Adolescents with Gender Identity Disorder
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Click-evoked otoacoustic emissions (CEOAEs) are echo-like sounds that are produced by the inner ear in response to click-stimuli. CEOAEs generally have a higher amplitude in women compared to men and neonates already show a similar sex difference in CEOAEs. Weaker responses in males are proposed to originate from elevated levels of testosterone during perinatal sexual differentiation. Therefore, CEOAEs may be used as a retrospective indicator of someone’s perinatal androgen environment. Individuals diagnosed with Gender Identity Disorder (GID), according to DSM-IV-TR, are characterized by a strong identification with the other gender and discomfort about their natal sex. Although the etiology of GID is far from established, it is hypothesized that atypical levels of sex steroids during a critical period of sexual differentiation of the brain might play a role. In the present study, we compared CEOAEs in treatment-naïve children and adolescents with early-onset GID (24 natal boys, 23 natal girls) and control subjects (65 boys, 62 girls). We replicated the sex difference in CEOAE response amplitude in the control group. This sex difference, however, was not present in the GID groups. Boys with GID showed stronger, more female-typical CEOAEs whereas girls with GID did not differ in emission strength compared to control girls. Based on the assumption that CEOAE amplitude can be seen as an index of relative androgen exposure, our results provide some evidence for the idea that boys with GID may have been exposed to lower amounts of androgen during early development in comparison to control boys.
KeywordsOtoacoustic emissions Gender Identity Disorder Gender Dysphoria Sex differences Androgen Sexual differentiation
We thank Mrs. Iris Franken-Boot, who kindly assisted with the data collection and helped with the patient recruitment. We further thank Dr. Ir. Emile de Kleine and Prof. Pim van Dijk from the University Medical Center Groningen, who kindly introduced us to the OAE equipment and provided us with example protocols for data collection. This study was funded by a VICI Grant (453-08-003) from the Dutch Science Foundation (Nederlandse Organisatie voor Wetenschappelijk Onderzoek) to J. Bakker. J. Bakker is a Senior Research Associate of the Belgian Fonds National de la Recherche Scientifique.
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