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Fertil Steril. 2008 Jul;90(1):56-9. Epub 2007 Sep 4.

A polymorphism of the CYP17 gene related to sex steroid metabolism is associated with female-to-male but not male-to-female transsexualism.

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Department of Gynecologic Endocrinology and Reproductive Medicine, Medical University Vienna, Vienna, Austria.



To assess the association between transsexualism and allele and genotype frequencies of the common cytochrome P450 (CYP) 17 -34 T>C single nucleotide polymorphism (SNP).


Case-control study.


Academic research institution.


102 male-to-female (MtF) and 49 female-to-male (FtM) transsexuals, 756 male controls, and 915 female controls.


Buccal swabs and multiplex polymerase chain reaction on a microarray system.


Analysis of the CYP17 -34 T>C SNP.


CYP17 -34 T>C SNP allele frequencies were statistically significantly different between FtM transsexuals and female controls (CYP17 T: 55/98 [56%] and CYP17 C: 43/98 [44%] versus CYP17 T: 1253/1826 [69%] and CYP17 C: 573/1826 [31%], respectively). In accordance, genotype distributions were also different between FtM transsexuals and female controls using a recessive genotype model (CYP17 T/T+T/C: 39/49 [80%] and C/C 10/49 [20%] vs. CYP17 T/T+T/C: 821/913 [90%] and C/C 92/913 [10%], respectively). The CYP17 -34 T>C allele and genotype distributions were not statistically significantly different between MtF transsexuals and male controls. Of note, the CYP17 -34 T>C allele distribution was gender-specific among controls (CYP17 C: males; 604 of 1512 [40%] vs. females; 573 of 1826 [31%]). The MtF transsexuals had an allele distribution equivalent to male controls, whereas FtM transsexuals did not follow the gender-specific allele distribution of female controls but rather had an allele distribution equivalent to MtF transsexuals and male controls.


These data support CYP17 as a candidate gene of FtM transsexualism and indicate that loss of a female-specific CYP17 T -34C allele distribution pattern is associated with FtM transsexualism.

[Indexed for MEDLINE]

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