Screwed makes a good point about treatable conditions which can mimic Alzheimer's and other neurodegenerative disorders. There are a large number of autoimmune diseases and infections which sometimes get diagnosed as Alzheimer's, and most can be treated and, if not cured, at least be controlled. Since many of these are very difficult to diagnose, the most important step is to eliminate the neurodegenerative diseases. For Alzheimer's, the best way is a amyloid pet scan, which can eliminate Alzheimer's as a diagnosis even though it can't directly confirm Alzheimer's (you can have amyloid plaques without having Alzheimer's, but you can't have Alzheimer's without amyloid plaques). And yes, thyroid autoimmune disease (Hashimoto's) is an example of an autoimmune disease which is sometimes diagnosed as Alzheimer's, and can be treated.