Treatment of hyperthyroidism can unmask azotemia associated with chronic kidney disease (CKD) because of the decline in glomerular filtration rate (GFR) after normalization of thyroid hormone concentrations,8 although the development of azotemia after treatment (with antithyroid medication or by thyroidectomy) is not associated with a reduced survival time in cats that remain euthyroid after treatment.9 Here, TG is linked to chronic kidney disease.