Mineral and Bone Parameters in Dialysis Patients Vary by Time of Day

Plasma phosphate levels demonstrated significant circadian variation, peaking around 3:30 a.m. with the nadir occurring around 11:00 a.m. In a study of 17 dialysis patients, the peak and nadir for ionized calcium were around 12:15 p.m. and 8:00 p.m., respectively; the peak and nadir for PTH were 5:45 p.m. and 10:15 a.m., respectively; and the peak and nadir for 25-hydroxyvitamin D were 9:45 a.m. and 4:00 p.m., respectively. FGF-23 did not show a significant circadian variation. Among 8 healthy volunteers, only phosphate and PTH levels demonstrated circadian variation. All participants of the Journal of Nephrology study were on controlled diets.