Mitochondria have a receptor site for estrogen (a hormone) called estrogen receptor β (ERβ). When estrogen attaches to this site, it promotes mitochondrial function. Studies have also suggested ERβ stimulation can cause cells to create new mitochondria. More mitochondria, or increased activity of existing mitochondria, in the cell might have an impact on patients with Alzheimer's disease. One way to measure this increase in function is to look for the presence of an enzyme called COX in your blood. If a drug increases mitochondrial function, there will be an increase in COX concentration in the bloodstream.