The Urinary Excretion of Galactose and its Significance in Clinical Intravenous Galactose Tolerance Tests

Tygstrup N. The urinary excretion of galactose and its significance in clinical intravenous galactose tolerance tests. The disappearance of galactose from the blood after intravenous administration may be used for measurement of the liver function, if correction for the urinary loss of galactose is made. The present study was performed in order to determine the significance of this loss. It was found that urinary excretion of galactose was unimportant in relation to hepatic elimination at plasma concentrations below about 500 mg/l (approximately 3 per cent of the total elimination), but at higher concentrations the ratio between urinary excretion and hepatic elimination increased, as the former rises with the concentration, and the latter remains constant. After a single injection of about 500 mg/kg body weight on an average 10 per cent of this amount was excreted in normal subjects as well as in patients with cirrhosis. This percentage could be used for a practical calculation of the contribution of the urinary loss to the total elimination rate of galactose during the interval in which the latter remains essentially constant. The experiments indicate a low renal threshold for galactose, but no evidence for a reabsorption Tm was found within the range of plasma concentrations studied (up to 3,000 mg/l). The renal clearance of galactose was significantly decreased in patients with cirrhosis. The implications of these findings for the calculation of the maximal hepatic galactose elimination rate from the plasma concentration curve following a single injection are examined in an appendix.