Contribution of androgen receptor sensitivity to the relation between testosterone and sexual desire: An exploration in male-to-female transsexuals

J Endocrinol Invest. 2010 Jan;33(1):37-41. doi: 10.1007/BF03346547. Epub 2009 Jul 20.


Background: Low sexual desire is present in 1/3 of male-to-female transsexuals (post-operative male-to-female transsexual persons on estrogen replacement). Several studies report lower endogenous testosterone (T) levels in this group compared to community dwelling women. However, no relationship between T and sexual desire has been found in male-to-female transsexuals. Considering its role in androgen sensitivity, cytosine-adenine-guanine (CAG) trinucleotide repeat sequence in the androgen receptor (AR) might modify the relationship between T levels and sexual desire in male-to-female transsexuals.

Aim: This study aims to assess the potential contribution of the number of CAG repeats in the association between T and sexual desire in male-to-female transsexuals. MATERIAL, SUBJECTS, AND METHODS: Thirty-four post-operative male-to-female transsexuals participated in a cross-sectional study. The Sexual Desire Inventory, a questionnaire measuring sexual desire, was completed. Serum levels of total (TT) and free T (FT), DHEA-S, SHBG, and LH were measured in morning blood samples. AR gene CAG repeat length was determined by automated DNA fragment analysis of exon 1 of the AR gene.

Results: The CAG repeat length ranged from 14 to 28 with a median of 21. CAG polymorphism was correlated with FT (r=0.389; p=0.023) but not with TT (r=0.191; p=0.280). The observed interaction between TT and CAG was significant only for solitary sexual desire (p=0.002). The interaction of CAG repeats and FT on sexual desire failed to reach significance.

Conclusions: We could not establish that CAG repeat length is a consistent modulating factor in the relationship between TT or FT and sexual desire in male-to-female transsexuals.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Cross-Sectional Studies
  • Dehydroepiandrosterone Sulfate / blood
  • Female
  • Humans
  • Libido* / physiology
  • Male
  • Middle Aged
  • Receptors, Androgen / genetics*
  • Receptors, Androgen / physiology
  • Sex Hormone-Binding Globulin / analysis
  • Testosterone / blood*
  • Transsexualism / blood*
  • Transsexualism / physiopathology*
  • Transsexualism / psychology
  • Transsexualism / surgery
  • Trinucleotide Repeats


  • AR protein, human
  • Receptors, Androgen
  • Sex Hormone-Binding Globulin
  • Testosterone
  • Dehydroepiandrosterone Sulfate