In this cohort, overall gray and white matter volumes were similar between XXY males and controls. Smaller temporal lobe volumes and STG volumes were found in the XXY group, although this did not persist after adjustment for total brain volume. However, when XXY individuals with and without testosterone supplementation were compared, it was found that the XXY individuals without testosterone supplementation had smaller temporal and STG volumes than did both XXY individuals who had received testosterone and healthy controls. The difference with controls survived covarying for total brain volume, although the difference with XXY + T did not. The KS − T group also had diminished scores in verbal fluency compared with the KS + T group. A limitation here is that when the overall cohort was identified prospectively, the groups who had chosen to take testosterone supplementation were self-selected, raising the question of whether there may have been functional differences before treatment in those individuals who sought out testosterone supplementation. Some support for baseline similarity between the KS + T and KS − T group was that both groups had similar IQ findings before the initiation of testosterone.
