Although a great deal of information is available regarding levels of circulating plasma insulin, not much is known of its extravascular and intracellular concentrations. A number of recent studies have measured insulin in bile, cerebrospinal fluid, and lymph, while this report is concerned with the usefulness and significance of urinary insulin in health and some disease states.
There are certain advantages in measuring insulin in urine. It reflects average serum levels over an extended period of time and is useful in situations in which repeated blood sampling is impractical, such as the newborn. Measurement of urine insulin is feasible in insulin-requiring diabetic patients for their serum antibodies do not usually pass the glomerulus. Finally, urine or lymphatic insulin may be a more valid reflection of the tissue concentration than the intravascular levels.
Methods
Assay Technique.—
Before sensitive immunologic methods were available, complicated extraction and purification techniques were necessary for the