My senior cat Yeowls morning

My other senior cat was diagnosed with kidney renal disease. She is doing ok despite this diagnosis surprises me. I have noticed that she is always hungry, constantly feeding her wet food, she doesn't eat dry anymore and she drinks alot water too. What noticed recently started yeowling not meowing like a loud in morning. I am not sure why she does this, she sleeps downstairs. What causes cat to yeowl? Is she uncomfortable, us it dimentia? I noticed I feed her after she quiets down.

Hyperthyroidism can cause this behavior. It is fairly common in senior cats.  It can be checked with  a blood test.