Circadian variation of serum urea concentration in north Indian subjects

Circadian rhythm of serum urea concentration was studied in 25 clinically healthy, diurnally active, nocturnally resting young male Indians. The mean urea concentration was observed to be 22.32 mg/dl at 0800 h which increased gradually reaching maximum at 0000 h with a mean of 31.00 mg/dl. A marked circadian variation in serum urea was recorded with a statistically significant amplitude and acrophase at 2232 h (Cosinor analysis). The observation that serum urea concentration oscillates physiologically in the peripheral blood according to a circadian rhythm may prove to be of importance in the clinical interpretation of values at different times along the 24 h light-dark period.