APOE and Alzheimer disease: Herein, we used volumetric MRI and Arterial Spin Labeling (ASL) to examine sex-specific associations of serum testosterone (both total and free testosterone) with regional GMV and CBF in cognitively normal midlife women and men at risk for late-onset AD (family history and/or Apolipoprotein E epsilon 4, APOE-4, genotype).