MedWire News: Study results suggest that low levels of calcidiol are more common in patients with chronic kidney disease (CKD) than in osteoporotic patients from the same geographical location.
The study findings may provide some clues to understanding the mechanisms underlying calcidiol deficiency and insufficiency.
Low exposure to sun and high latitude could predispose to calcidiol insufficiency, although this remains a controversial hypothesis – and no previous study has compared calcidiol levels in two high-risk populations from the same geographical area.
Calcidiol deficiency has already been found to be common in both CKD and osteoporotic patients, with inverse associations between calcidiol and PTH levels in both populations. To explore the contribution of environmental and other factors to calcidiol insufficiency and deficiency, Vincent Pichette, from the University of Montreal in Canada, and colleagues measured calcidiol levels in 160 predialysis CKD patients and 53 osteoporotic patients from a single center. Calcidiol insufficiency was defined as ranging from 37.5 to 75.0 nmol/l and deficiency as a level below 37.5 nmol/l.
Calcidiol insufficiency or deficiency was present in almost all (98.7%) of the predialysis patients and around half (50.9%) of the osteoporotic patients. Thus calcidiol insufficiency and deficiency were more common in CKD patients than in a similar osteoporotic population, say the authors, “suggesting a cause unrelated to environmental factors.”
The team also found that calcidiol levels were significantly lower in diabetic than nondiabetic predialysis patients, as well as lower in predialysis than in osteoporotic patients.
When the authors stratified patients in the predialysis group for treatment with active vitamin D sterol, the observed inverse correlation between calcidiol and PTH remained significant only in untreated patients, while stratification for presence of diabetes showed a significant inverse correlation in diabetic patients only.
The investigators also found that inadequate calcidiol levels were more prevalent in osteoporotic patients not treated than treated with vitamin D (66.7% vs 47.5%). But mean calcidiol levels were still significantly lower in CKD patients than in the untreated osteoporotic patients.
This result argues against exposure to the sun being the major factor affecting calcidiol levels in CKD, Pichette et al remark.
“Although observational data prohibit causal inference, our study supports the hypothesis that CKD reduces calcidiol levels and that this situation is affected by several factors,” the team comments further in the journal International Urology and Nephrology.
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