ABSTRACT

Although <1% of secreted cortisol normally appears unchanged in urine, about 30% of cortisol metabolites are excreted by canine kidneys (less in felines), because they are variably protein-bound. Peptide and smaller protein hormones are filtered to some degree by glomeruli, but they usually undergo tubular reabsorption and degradation within proximal tubular epithelial cells, so that only a small fraction finally appears in urine.