I'm not sure what you want to know about it, but yes, hyperthyroidism is very common in older cats. It is easily treated either with tablets or by surgery to remove the over-active throid gland. It may also be treated with radio-active iodine although this is not a common treatment as the cat has to stay at the vets for a long time. Hyperthyroid cats often have a big appetite but lose weight, often have mild diarrhoea, become more anxious and irritable and can develop a scruffy coat. Take your cat to the vet for diagnosis of hyperthyroism (usually by a blood test) and treatment. Hope this answers your question.