Uromodulin

Uromodulin is a protein produced exclusively by the tubule cells of the thick ascending limb of the loop of Henle in the kidneys and is released into both the tubule lumen and the bloodstream. Uromodulin is polymerised in the distal tubule lumen, where it has a protective effect against kidney stone formation, among other things. Due to its polymer structure, uromodulin released via the urine is only suitable to a limited extent for the exact measurement of protein concentration. Unlike in urine, uromodulin in serum occurs exclusively as a monomer and can therefore be quantified more reliably. 

Furthermore, urinary uromodulin concentration shows only a weak association with estimated glomerular filtration rate (eGFR). The serum uromodulin concentration (sUmod), however, correlates strongly with eGFR. 

The sUmod concentration, in contrast to other glomerular markers such as creatinine and cystatin C, enables the identification of early stages of chronic renal insufficiency already in the asymptomatic phase. A decrease in sUmod concentration indicates a loss of function and integrity of the renal parenchyma as renal failure progresses. 

The sUmod level can also be used to predict long-term complications. Epidemiological studies show that low levels of sUmod are associated with increased overall mortality, cardiovascular morbidity, heart failure and progression to renal failure. In addition, low sUmod concentrations are predictive of long-term loss of transplant function. 

Serum uromodulin is a sensitive marker that provides information about tubular function and can be helpful in the prediction and early detection of renal function deterioration, especially in diseases that mainly affect the renal tubules.