Update on Tigger. Test results show his thyroid is normal. Only indicators out of normal are two regarding heart function. Those blood test results plus the vet's exam of him hearing a galloping heart mumrmur have resulted in his royal kitty self being put on a low dose of the heart med Benazapril. I'm to take him back for a recheck and follow up blood work in a month.
Still don't know why he is eating so much and yet still losing weight. I'm to get a stool sample from Tigger to the vet to check for any blood in the stool or other problems. It may just be that old age has his heart showing problems and that the elevated heart rate is burning so many more calories that he is hungry all the time and yet has an aged digestive track that doesn't absorb nutrients well. No clear answers yet other than old age issues but despite that, Tigger is doing impressively well for a 20 to 22 year old cat! So he's now on a heart med along with his arthritis med to supplement lots of love and attention. He keeps me well trained and spoiled rotten. :-)