Circadian rhythm of urinary beta 2 microglobulin excretion in patients with a nephrotic syndrome

The changes in urinary beta 2 microglobulin excretion during the day were studied in 20 patients with a nephrotic syndrome under standardized conditions and compared with the known circadian variations in urinary albumin excretion in the same patients. Fifteen of the 20 patients (75%) had a circadian rhythm for beta 2 microglobulin in the urine. Phase as well as relative amplitude of the beta 2 microglobulin circadian rhythm varied between patients. In addition, its presence, normality, amplitude and phase were largely different from the albumin rhythm. Observations made in 10 healthy individuals suggest that day-night variability in the excretion of beta 2 microglobulin and albumin in the urine is also present in the absence of clinically important proteinuria. Circadian variations in urinary beta 2 microglobulin excretion are found in a majority of the patients with nephrotic syndrome and as they differ in several respects from the day-night fluctuation in urinary albumin excretion the mechanism is probably different.