title: Typical female 2nd-4th finger length (2D:4D) ratios in male-to-female transsexuals-possible implications for prenatal androgen exposure.
abstract: Prenatal exposure to androgens has been implicated in transsexualism but the etiology of the condition remains unclear. The ratio of the 2nd to the 4th (2D:4D) digit lengths has been suggested to be negatively correlated to prenatal androgen exposure. We wanted to assess differences in 2D:4D ratio between transsexuals and controls. Sixty-three male-to-female transsexuals (MFT), 43 female-to-male transsexuals (FMT), and 65 female and 58 male controls were included in the study. Photo copies of the palms and digits of the hands were taken of all subjects and 2D:4D ratios were measured, according to standard published procedures. Comparison between right-handed individuals revealed that the right-hand 2D:4D in MFT is higher than in control males but similar to that observed in control females. In FMT we found no differences in 2D:4D relative to control females. Our findings support a biological etiology of male-to-female transsexualism, implicating decreased prenatal androgen exposure in MFT. We have found no indication of a role of prenatal hormone exposure in female-to-male transsexualism.
authors.affiliation: Clinical Neuroendocrinology Group, Max Planck Institute of Psychiatry, Kraepelinstrasse 10, 80804 Munich, Germany. schneider@mpipskyl.mpg.de
authors.forename: Harald J
authors.initials: HJ
authors.lastname: Schneider
authors.forename: Johanna
authors.initials: J
authors.lastname: Pickel
authors.forename: Günter K
authors.initials: GK
authors.lastname: Stalla
mesh_terms: D000728:Androgens / Q000009:adverse effects / Q000502:physiology*; D000886:Anthropometry; D005260:Female; D005385:Fingers / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D009929:Organ Size; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012727:Sex Characteristics; D012733:Sex Differentiation / Q000502:physiology; D018709:Statistics, Nonparametric; D014189:Transsexualism / Q000209:etiology
chemical_list: D000728:Androgens