Chronic kidney disease is a main confounding factor for 25-vitamin D measurement

Hyperuricemia is associated with secondary hyperparathyroidism in patients with chronic kidney disease

PURPOSE

Hyperuricemia is common among patients with chronic kidney disease (CKD). In the general population, hyperuricemia is associated with secondary hyperparathyroidism (SHPT), in a mechanism that involves vitamin D metabolism. Data for patients with CKD, however, are scarce. We aimed to evaluate the relationship between hyperuricemia and mineral and bone metabolism, particularly hyperparathyroidism.

METHODS

This is a retrospective study that included 922 adult patients with stages 3, 4, or 5 CKD, not on dialysis. Clinical, demographic, and biochemical data were collected from charts and included uric acid, parathyroid hormone (PTH), 25(OH)-vitamin D, calcium, phosphate, renal function (estimated glomerular filtration rate-eGFR), and medications such as allopurinol, furosemide, and cholecalciferol. SHPT was defined as PTH > 65 pg/ml.

RESULTS

Our patients were mostly Caucasian women, with a mean age of 64 ± 16 years. SHPT and hyperuricemia were observed in 70% and 62.4% of patients, respectively. Patients with SHPT presented higher levels of uric acid (7.2 ± 1.8 vs. 6.6 ± 1.7 mg/dL, p = 0.0001) and a higher frequency of hyperuricemia (66% vs. 33%, p = 0.0001). Patients with hyperuricemia were mostly female, with lower eGFR, higher phosphate, and higher PTH. The risk of hypovitaminosis D was higher among patients with SHPT (69.7% vs. 53.1%, p = 0.0001). Hyperuricemia remained independently associated with hyperparathyroidism, (p = 0.033) even after adjustments for eGFR, calcium, phosphate, hypovitaminosis D, and use of allopurinol, calcitriol, furosemide, and cholecalciferol.

CONCLUSION

Hyperuricemia seems to be a contributing factor for SHPT in patients with CKD. The mechanisms behind this finding have yet to be elucidated.