Separating out brain structural changes due to low testosterone levels from those due to dosage effects of other genes cannot be done with the existing data, but the possibility that insufficient testosterone is contributing to smaller gray matter volumes is supported both by the observation of more pronounced gray matter decreases in 47,XXY males than in 47,XXX females [Patwardhan et al., 2002], and by the finding in one study that gray matter deficits were less pronounced in males who had testosterone supplementation than those who did not [Patwardhan et al., 2000].
