Because it often starts slowly in older cats, owners may put the early signs down to age. Untreated, hyperthyroidism can lead to heart disease, high blood pressure and blindness, so a vet check is worth it for any older cat that's losing weight.
Diagnosis is usually straightforward: a blood test shows a high T4 level in most cats, and your vet may feel an enlarged thyroid in the neck. Because hyperthyroidism can mask kidney disease, your vet will check kidney function before and during treatment.
