Neufang and colleagues used voxel based morphometry to explore sex differences, including the influences of sex steroid levels and pubertal stage to GM and WM densities in a sample of 46 males and 46 females aged 8-15 years (Neufang et al., 2009). In girls, the hippocampus was larger bilaterally, as was the right striatum. In boys, a region of the amygdala was larger in males. With the exception of higher levels of serum testosterone in older males, there were no differences in sex steroid levels in their sample. They first examined the relationship of steroid levels and pubertal stages to brain structure in regions that had already been demonstrated to be sexually dimorphic; they found that GM intensity in the amygdala was predicted by testosterone levels in both males and females. Testosterone levels also predicted hippocampal size in females, but with younger females having larger hippocampi. In a whole brain regression analysis, testosterone was positively associated with increased GM density in right sided diencephalic structures in males, and negatively correlated with parietal GM volume in males. Estradiol levels were positively
