The relation of glycosuria to glycaemia and the determination of the renal threshold for glucose

INTRODUCTION.GLYCOSURIA, as the most obtrusive finding in diabetes mellitus, has, since its association with this disease was established, aroused considerable interest both as to its production and as to its significance.Prior to the day of Claude Bernard the presence of sugar in the blood was regarded as denoting an abnormal and definitely pathological condition, and glycosuria was considered to be its attendant, and equally pathological, manifestation.His demonstration that glycaemia was of normal occurrence, and that hyperglycaemia was productive of glycosuria, was the first step towards the modern ideas on the subject, and, in addition, it provided the data upon which Bernard [1877] based his conception of the renal threshold as that level of sugar in the blood at which glycosuria appeared.Some years later the discovery by von Mering [1888] of phlorhidzin diabetes showed that glycosuria could exist apart from hyperglycaemia, but it was only with the realisation that there existed a benign clinical type of this disorder that the idea of the presence of a renal factor in all cases of glycosuria became generally accepted.Apparently Bernard was of the opinion that when the sugar in the blood exceeded a certain level the kidney permitted sugar to "spill" over into the urine.A definite line could therefore be drawn between glycosuria and aglycosuria.This idea was universally accepted until it was attacked by Benedict, Osterberg and Neuwirth [1918].They maintain that, in the urine of normal individuals, sugar is always present, and that, after carbohydrate meals, an increase in amount may be detected.They have suggested the term glycuresis for this phenomenon, and claim that there is no such thing as a definite threshold.Folin and Berglund [1922] have criticised this work on the ground that the carbohydrates present in normal urine are not of the nature of glucose, but are unusable carbohydrates which the body naturally excretes.Until glucose has been isolated from normal urine this conception of glycuresis must be considered unproven.The work of Richards [1929] has produced very strong evidence in favour of the filtration-reabsorption theory of kidney function and considered along