Baldur and the vet
Them: Do you think he would eat if --
Me: Yes.
Them: He seems awfully upset.
Me: Don't put any body parts you care about between him and the food.
Them: Does he have any food preferences?
Me: Already dead is best; he's not a mighty hunter.
When I picked him up they confirmed that they had slid a bowl of canned food into his kennel, covered the kennel (to try to calm him down; didn't know that wasn't just a bird thing), and immediately heard much slurping and chomping. That's my little vacuum cleaner!
Baldur has been losing roughly 2 ounces per week since early November despite starting then to treat him for hyperthyroidism (and despite the fact that he has all the food he wants), so my vet and I are concerned. We did assorted blood tests that were mostly normal -- T4 still good, WBC fine, PTH low, calcium tending high over the last year or so, ionized calcium high, ALT a little high). She recommended a tumor hunt and also, because he has a heart murmur, a look at the heart.
We've spoken briefly but she didn't yet have the report, so we'll talk more on Monday. The X-ray was fine, she said, and the ultrasound mostly fine (no tumors). She reported that his liver is bigger than it should be and "speckled", whatever that means. Also his bile ducts are a little dilated -- nothing like what Erik had, but not completely normal. I asked what this means and she said she's not sure but her working hypothesis is cholangiohepatitis -- what his brother has. (What's wrong; wasn't catching the hyperthyroidism wave enough? :-) )
When I picked him up they gave me a copy of the report, which says: "Assessment: Chronic hepatic disease (cholangitis/cholangiohepatitis, other) is suspected based upon the sonographic appearance of the liver, long term chronic low grade ALT elevation and chronicity of weight loss. Other causes of liver disease (lymphoma, mast cell tumor, hepatic lipidosis) have not been excluded but the degree of chronicity would be unusual. A cause for the hypercalcemia was not identified. Differential diagnoses include idiopathic hypercalcemia (likely) and occult neoplasia."
I am glad I live in the Google age, because otherwise I wouldn't have known what some of that meant. "Occult neoplasia" is med-speak for "hidden tumor", just to save you the search.
So there isn't a big obvious cause yet, which is both good and bad (depending entirely on whether big obvious causes would have been fixable). But it's very weird for the "big" cat to be under 11 pounds, so if it is cholangiohepatitis I hope treating it fixes that.

no subject
I'm not surprised that covering the kennel worked -- my Narshie was quite the "out of sight, out of mind" kind of girl. She sometimes hid her head under a towel at the vet's to make things go away. Then again, she was NOT like your Baldur in the eating department. I'm not sure she ever ate food while at a vet.
no subject
I learned more about what happened at the vet's today. Apparently the first time they put a bowl of food in he pushed it right back out with some force, growling all the while. They cleaned that up and tried again, being ready to close the door quickly, and that time they covered the kennel -- at which point he ate ~3oz of canned food in not very long.
My vet has a theory that maybe he's just getting pickier, particularly since I had to switch the dry food that's down all the time on account of Embla's kidney problems. I mean, I see Baldur eating what looks like plenty, but if he's cut down some, would I really notice? So the new plan is to give him larger quantities of canned food (should be fun keeping Embla away...) and see what that does. (He's 17; how bad can it be if he becomes addicted to the fattening more-expensive stuff?)