A direct evidence of changes in brain aromatase expression under neurodegenerative conditions in humans has been obtained in postmortem studies of multiple sclerosis lesions, where the enzyme is upregulated in astrocytes in male patients.116 Aromatase immunoreactivity is also increased in the hippocampus21 and the prefrontal cortex38 of male and female AD patients, compared with sex- and aged-matched controls. The gene discussed is CYP19A1; the disease is Alzheimer disease.