Hyponatremia at the time of initiation of maintenance hemodialysis (HD) is associated with an elevated risk of mineral bone abnormalities and death, new findings show.
In a study of 6,127 HD patients—including 775 who had hyponatremia and 5,278 with normal sodium levels—Sagar U. Nigwekar, MD, and colleagues at Massachusetts General Hospital in Boston found that hyponatremia is associated with a significant twofold increased risk of hypercalcemia after adjusting for numerous potential confounders, according to findings published online ahead of print in the American Journal of Kidney Disease. Hyponatremia also is associated with a significant 29% increased risk of hypoparathyroidism, a significant 33% increased risk of elevated alkaline phosphatase, and a significant 42% increased risk of death.
“Although the exact sequence of events describing hyponatremia leading to mineral bone abnormalities is unknown, we speculate that associations between hyponatremia and these mineral abnormalities are derived from the direct actions of hyponatremia on bone,” the authors wrote.
The investigators explained, for example, that hyponatremia may directly stimulate osteoclastic activity, increasing calcium levels and, consequently, suppressing parathyroid hormone.
Dr. Nigwekar’s group noted that the associations between hyponatremia and markers of bone turnover they found raise the possibility that hyponatremia may contribute to osteoporosis in the HD population, but cautioned that their interpretations regarding these associations are hypotheses and cannot be proved by an observational study such as the one they conducted.