Potential biomarkers were measured in peripheral blood of individuals with Alzheimer's disease (AD) and in healthy controls: (1) plasma concentrations of homocysteine, cortisol, prolactin, melatonin, neurotrophin BDNF, and coenzyme Q10, (2) the concentration of BDNF and the activity of monoamine oxidase type B, citrate synthase, complexes I, II and IV of the mitochondrial respiratory chain, and glycogen synthase kinase-3β (GSK3β) in platelets, (3) transcription factor CREB activity in lymphocytes, (4) respiration rate in platelet mitochondria, (5) gene polymorphism of the apolipoprotein E (APOE ), serotonin transporter (5-HTT), BDNF, serotonin receptor 2A (5-HT2A), and heat shock proteins (HSP70). The association of these parameters was analyzed with risk and progression of AD.