In contrast, Tamm‐Horsfall protein excretion decreases in cats associated with decreases in its production by damage to distal tubular cells.11 Carboxylesterase 5A (also known as cauxin), which produces a sex pheromone,12 is a major urinary protein in normal healthy cats13 and its excretion is decreased in cats with CKD due to decrease of number of proximal tubular cells expressing it.14, 15, 16, 17 The increase of urinary excretion of these proteins usually results from functional, structural, or both damages in the glomerulus and renal tubules. The gene discussed is CES5A; the disease is chronic kidney disease.