Impact of hyponatremia on bone, a narrative review

Hyponatremia is one of the most common electrolyte disorders encountering both in hospitalized and in outpatients. Across the past decades, several cross-sectional and observational studies have shown a strong association between low serum sodium levels and adverse bone outcomes such as osteoporosis, falls, and fractures, suggesting a potential direct link between serum sodium disturbances and bone health. However, association does not necessarily imply causality. Data from preclinical studies have shown a possible causative relationship between hyponatremia and activation of osteoclasts with consequent bone resorption, whereas clinical studies so far have shown mostly an association with increased bone formation rather than affection of bone resorption. In this narrative review, we provide an overview of the current evidence on the relationship between serum sodium disorders and bone health, starting with preclinical findings, followed by cross-sectional and association data and concluding with insights from prospective and interventional studies.