NDT Advance Access published online on June 10, 2008
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfn302
Bone mineral metabolism and its relationship to kidney disease in a residential care home population: a cross-sectional study
1 Department of Clinical Biochemistry 2 Department of Health Care of the Older Person 3 Department of Renal Medicine, East Kent Hospitals NHS Trust, Canterbury, Kent, CT1 3NG, UK
Correspondence and offprint requests to: Joanne L. Carter, Department of Clinical Biochemistry, East Kent Hospitals NHS Trust, Canterbury, Kent, CT1 3NG, UK. E-mail: joanne.carter{at}ekht.nhs.uk
| Abstract |
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Background. Institutionalized older people have a high risk of bone fractures due to osteoporosis. In addition, chronic kidney disease (CKD) is highly prevalent in older people living in residential homes. Secondary hyperparathyroidism, poor calcium intake and deficiency of 1,25-dihydroxyvitamin D may lead to decreased bone mass in people with CKD. The present cross-sectional study assessed the relationship between markers of bone mineral metabolism and kidney function in a residential care home population.
Methods. Older subjects were recruited from residential care homes and kidney function stratified by the estimated glomerular filtration rate (GFR). Parathyroid hormone (PTH), 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were measured in 188 residents not receiving vitamin D/calcium treatment [mean age 85 (range 68– 100) years, 75% female] and in 52 residents receiving vitamin D/calcium supplementation.
Results. Amongst those not receiving vitamin D/calcium, median PTH increased with declining GFR (P < 0.0001), particularly as GFR (mL/min/1.73 m2) fell below 45. PTH concentration was suppressed by increasing 25-hydroxyvitamin D (P < 0.0001), but not 1,25-dihydroxyvitamin D (P > 0.05) concentration. Nearly all residents (92%) had 25-hydroxyvitamin D deficiency or insufficiency and this was uninfluenced by kidney function (P > 0.05). Concentration of 1,25-dihydroxyvitamin D declined with worsening renal function (P < 0.0004) but 1,25-dihydroxyvitamin D deficiency was prevalent at all stages of kidney disease, including amongst residents receiving vitamin D/calcium supplementation.
Conclusion. Vitamin D deficiency and secondary hyperparathyroidism are common in this population irrespective of renal function. However, as GFR falls below 45, the prevalence of secondary hyperparathyroidism and 1,25-dihydroxyvitamin D deficiency increases. Unidentified CKD appears to exacerbate secondary hyperparathyroidism in this at risk population.
Keywords: 1,25-dihydroxyvitamin D; 25-hydroxyvitamin D; chronic kidney disease; older people; parathyroid hormone
Received for publication: 20.12.07
Accepted in revised form: 5. 5.08