The importance of aromatase as a neuroprotective molecule in humans is suggested by the existence of genetic variants of the enzyme that confer an increased risk for Alzheimer’s disease25–28. These genetic variants of aromatase may result in decreased oestradiol synthe¬sis in the brain, which, together with decreased serum oestradiol levels in postmenopausal women or serum testosterone levels in aged men, may increase the risk for developing neurodegenerative diseases. In this regard, it is of interest that aromatase expression is increased in astro¬cytes in the human prefrontal cortex in the late stages of Alzheimer’s disease, a phenomenon that has been inter¬preted to be part of a rescue programme29.