Hi Beth,
there is a number of conditions that can cause hair loss. Little patches would make me think infection but you say your vet ruled that out? (both bacterial and fungal?) Gland/hormonal disorders can also cause hair loss but typically not in this type of pattern.
http://www.peteducation.com/article.cfm?c=2+2111&aid=421
Age by itself is not a disease, but with age things might not be working as well as they used to. There still should be a discernible cause, though, IMO.
Is this issue in any way seasonal?
Makes me think of Jasmine, though. Twice she developed a bald patch in different areas, which didn’t seem to have any reason for it. For lack of any better explanation, her vet put her on Melatonin and the fur grew right back.
I will let Dr. Krista address your specific blood questions. Were you interested in the holistic approaches to evaluating blood work? Also, not being able to tolerate an occasional eating splurge is considered an early warning sign that a dog is not completely healthy, so there would be many things to do at this point.
I wonder if Cookie has had prior digestive issues?