Cat refusing to eat

My 11 year old neutered male cat suddenly stopped eating on his own last week. Within a day he became lethargic barely able to put weight on his hind legs. He has lost a lot of weight. I tried changing foods but he will only eat liquide treats out of my hand.   I took him to the vet 3 times since they did a full body X-ray and found gas in his stomach. All other blood tests came out normal. Only the TSH came at <.1 maIU/L and free T4 11.83 pmol/L.   Vets could not find anything wrong with him and sent us home with some appetite enhancer and vitamin. It's been 4 days since last visit and I am still having to hand feed him.   I need suggestions on what could be the issue here, how can I get him to eat again or if there're some other tests I should get done. Thanks for reading.

Hello - I'm afraid that I'm not sure what other bloods your cat has had done, but as he is still not eating he will need a repeat visit to the vets.  The vets job is two-fold;  1) treating the symptoms eg maintaining hydration where animals are becoming dehydrated, treating pain where they are painful etc and 2) trying to find the cause of the symptoms / any changes on the bloods. Regarding the latter, did the bloods that they took rule out pancreatitis?  Is it a possibility that he could be in pain (that is difficult to tell in a cat)?   A good question for your vets is:  'What differentials have you ruled out?' And 'What could still be going on to cause the drop in appretite'  and 'which of those possibilities is most likely?' We do not analyse bloods on this site I'm afraid, but the answers to these questions should offer some direction to work in.  Best of luck and please let us know what you find.