Balding cat stopped eating

I thought I'd ask if anyone had any ideas

My boyfriend's 16 year old cat is in trouble. She started losing fur a while back, then she started eating less and less and now it seems she won't eat at all, and of course she's drastically losing weight. They tried switching her food from the high quality dry food to some higher quality soft food and she only started throwing up everywhere. They took her to the vet a few times, got some blood work done and found out it's not hyperthyroidism, diabetes, and in fact they found nothing out of the ordinary.

Anyone have any ideas as to what could be causing this, or better what to do about it?

Has she had x-rays? sometimes a mass can cause these symptoms, whether benign or malignant. Another thing that can cause reduced eating is dental issues. Have her teeth been checked. Frankly, with both the weight loss and hair loss I am surprised it wasn't thyroid. Perhaps another vet check is in order.

One of our cats stopped eating because of a developing liver cancer. About a month later, she was dying because we hadn't seen it before. I recommend a vet check ASAP. It might be nothing, but if we'd gone earlier, it could've saved poor Lady.

I miss her

They put her down.

Sorry to hear that. :(