Vitamin D Insufficiency and Deficiency in Chronic Kidney Disease

Abstract

Kidney disease has been identified as a risk factor for vitamin D deficiency in hospitalized patients, and low levels of 25-hydroxyvitamin D have been suggested to be a risk factor for hyperparathyroidism in patients with chronic kidney disease (CKD). However, little is known about the magnitude of vitamin D deficiency in patients with CKD living in the United States. In this regard, we examined the levels of 25(OH)D in 43 patients with CKD and serum creatinine between 1 and 5 mg/dl (calculated glomerular filtration rate 111-11 ml/min per 1.73 m2) as well as in 103 patients undergoing hemodialysis. In the predialysis patients, we found that 37 of the 43 patients (86%) had suboptimal levels of vitamin D (<30 ng/ml). Regression analysis indicated that there was a negative correlation between 25(OH)D and intact parathyroid hormone (PTH). Alkaline phosphatase showed a similar but less sensitive relationship. Serum albumin levels correlated with 25(OH)D levels. In contrast to findings reported in normal individuals, the levels of calcitriol correlated with those of 25(OH)D in the patients with CKD. In the group undergoing maintenance hemodialyis, we found that 97% of the patients had vitamin D levels in the suboptimal range, and there was no correlation of 25(OH)D levels with either PTH or serum albumin values. These data indicate that vitamin D insufficiency and deficiency are highly prevalent in patients with CKD and may play a role in the development of hyperparathyroidism. The functional significance of low levels of 25(OH)D in patients with stage 5 CKD remains to be determined.