Background. The occurrence of mixed dementia defined as the association of Alzheimer's disease with vascular dementia is increasing due to the global aging of the human population. Since thyroid hormones play a role in cognition and alterations of the thyroid axis occur with aging it is reasonable to assume that thyroid function and cognitive decline in mixed dementia are linked.Objective. To investigate whether there is a link between TSH, oxidative stress, cognitive decline and depression in female patients with mixed dementia.Methods. Fourty female patients with mixed dementia and 10 healthy controls were included in the study. MMSE, depression score (Cornel Scale of depression), TSH, MDA, glutathione were determined. Serum TSH levels correlated with the cognitive decline measured by MMSE (r=0.55 p=0.0002) and with de depression score (r=0.34 p=0.0314). Furthermore an increase in the oxidative stress marker MDA (p=0.0004) and in the antioxidant defense marker Glutathione (p=0.0013) was observed in patients with mixed dementia. In addition the levels of Glutathione correlated with cognitive decline (r=-0.4997 p=0.001) and with the levels of TSH (r=-0.4997 p=0.001). Conclusion.Our results suggest that thyroid function, oxidative stress and mixed dementia are corelated. However, a possible cause and effect relationship is not yet proved.

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