Background: The N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a well-known hormone used for the clinical diagnosis and evaluation of patients with heart failure. Its half-life is only 60 to 120 minutes may vary depending on the time of day, and its circadian variation is undetermined. The efficacy of NT-proBNP may be affected if there is circadian variation, and normal values may fluctuate depending on the time of day.

Objective: To determine the difference in NT-proBNP levels in healthy volunteers at varying times of the same day.

Materials and Methods: The present study enrolled a total of 30 healthy volunteers who were over 20 years old and had normal physical examination, renal function, liver function, chest radiography and electrocardiography in the year preceding study enrollment. The volunteers did not take any medication, including vitamins or energy drinks, in the week before enrollment. Blood samples for NT-proBNP levels were collected at 8.00 AM, 12.00 noon, 4.00 PM, 8.00 PM and 12.00 midnight on the same day.

Results: The present study enrolled a total of 30 volunteers, most of whom were female (66.6%). Their mean age was 30.30+5.98 years old; mean BMI was 20.34+3.57 kg/m2; mean serum creatinine was 0.79+0.16 mg/dL; mean serum AST was 21.8+5.4 IU/L; and mean serum ALT was 22.57+6.51 IU/L. The mean levels of NT-proBNP at 8.00 AM, 12.00 noon, 4.00 PM, 8.00 PM and 12.00 midnight were 36.2+29.9 pg/mL, 35.4+30.3 pg/mL, 39.0+40.9 pg/mL, 32.4+36.1 pg/mL and 23.8+20.3 pg/mL, respectively. There was no significant difference in NT-proBNP levels over the various time periods.

Conclusion: The levels of NT-proBNP of healthy volunteers did not show any circadian variation; however, the levels of NT-proBNP tended to be highest at 4.00 PM and lowest at 12.00 midnight.

Keywords: N-terminal pro-B-type natriuretic peptide, NT-proBNP, BNP, Heart failure, Healthy volunteers