Patients with end-stage renal disease (ESRD) exhibit circadian variation in mineral and bone parameters, according to a new study.

These parameters include blood levels of phosphate, calcium, parathyroid hormone (PTH), and 25-hydroxyvitamin D.

“Our results suggest that random testing of bone mineral parameters in ESRD, and treatment decisions based on such results, should consider the circadian pattern particularly when values are close to the boundaries of the desired range,” researchers stated in a report published online ahead of print in the Journal of Nephrology.

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In addition, guidelines for managing bone mineral parameters in ESRD patients need to consider circadian changes in the recommendations, they noted.

Hariprasad Trivedi, MD, of the Medical College of Wisconsin in Madison, and collaborators studied 17 ESRD patients on long-term hemodialysis and 8 volunteers without kidney disease who served as a control group. Phosphate binders, vitamin D analogues, and calcimimetics were discontinued.

For 5 days thereafter, participants consumed a diet controlled in calcium (1,200 mg per day) and phosphorus (1,000 mg per day). On day 6, which was a non-dialysis day for the ESRD patients, subjects underwent 12 2-hour blood draws for phosphate, ionized calcium, PTH, total 25-hydroxyvitamin D, and fibroblast growth factor-23 (FGF-23).

In the ESRD patients, plasma phosphate demonstrated significant circadian variation, with a peak occurring around 3:30 a.m. and nadir occurring around 11:00 a.m. The peak and nadir for ionized calcium was 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. For 25-hydroxyvitamin D, they were 9:45 a.m. and 4:00 p.m. The researchers observed no circadian variation in levels of FGF-23. In the control group, only phosphate and PTH levels demonstrated circadian variation.