The CYP17 MspA1 Polymorphism and the Gender Dysphoria.

INTRODUCTION

The A2 allele of the CYP17 MspA1 polymorphism has been linked to higher levels of serum testosterone, progesterone, and estradiol.

AIM: To determine whether the CYP17 MspA1 polymorphism is associated with transsexualism.

METHODS

We analyzed 151 male-to-female (MtF), 142 female-to-male (FtM), 167 control male, and 168 control female individuals. Fragments that included the mutation were amplified by PCR and digested with MspA1. Our data were compared with the allele/genotype frequencies provided by the 1000 Genomes Data Base, and contrasted with a MEDLINE search of the CYP17 MspA1 polymorphism in the literature.

MAIN OUTCOME MEASURES: We investigated the association between transsexualism and the CYP17 MspA1 polymorphism.

RESULTS

A2 frequency was higher in the FtM (0.45) than the female control (0.38) and male control (0.39) groups, or the MtF group (0.36). This FtM > MtF pattern reached statistical significance (P = 0.041), although allele frequencies were not gender specific in the general population (P = 0.887). This observation concurred with the 1000 Genomes Data Base and the MEDLINE search.

CONCLUSION

Our data confirm a sex-dependent allele distribution of the CYP17 MspA1 polymorphism in the transsexual population, FtM > MtF, suggestive of a hypothetical A2 involvement in transsexualism since the allele frequencies in the general population seem to be clearly related to geographic origin and ethnic background, but not sex.