Influence of physical mobility and season on 25-hydroxyvitamin D-parathyroid hormone interaction and bone remodelling in the elderly

Abstract

Objective: To investigate in¯uences of physical mobility and season on 25-hydroxyvitamin D±intact parathyroid hormone (iPTH) interaction in the elderly. Design: We examined 188 frail institutionalized elderly at the expected nadir of their serum vitamin D concentrations (winter). This group was compared with 309 healthy ambulatory elderly at the expected time of maximum vitamin D repletion (summer), to accentuate the in¯uences of season and physical activity. Methods: Serum concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, iPTH and urinary deoxypyridinoline (DPD) were measured. Results: Vitamin D metabolites were signi®cantly lower in the institutionalized elderly (P<0.0001), with an 82.5% prevalence of vitamin D de®ciency (25-hydroxyvitamin D <12 ng/ml) in institutionalized elderly in wintertime and 15.5% in ambulatory elderly in summertime. Overall, median iPTH did not differ between groups. However, median iPTH secretion in the presence of low vitamin D serum concentrations (5±30 ng/ml) was greater in ambulatory elderly. This could be explained by lower mobility status being correlated with greater serum calcium concentrations (r=0.24, P=0.02 in women; r=0.35, P=0.001 in men) and greater urinary excretion of DPD (r=0.41, P=0.0001 in women; r=0.42, P=0.0002 in men), independent of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and iPTH. Conclusions: These data support the hypothesis that immobility, even in the presence of vitamin D de®ciency, acts as an overriding in¯uence on bone metabolism by promoting bone resorption (measured as urinary DPD) and increasing serum calcium independent of iPTH. Therefore mobility status may substantially affect 25-hydroxyvitamin D threshold values and the degree to which patients bene®t from vitamin supplementation.

Genetic markers of bone and joint health and physical capability in older adults: the HALCyon programme

“…Lower levels of serum calcium have been associated with increased risk of vertebral fractures [13], though there is so far little evidence for associations with physical capability [14,15]. In addition to factors such as immobility [16] and inactivity [17] being associated with higher serum calcium in the elderly, there is also a genetic component, with an estimated 33% heritability [18], and genome-wide association studies (GWAS) have found that the T allele of SNP rs1801725 (A986S) of the calcium-sensing receptor gene ( CASR ) is associated with increased serum calcium [19,20].…”

How to select the doses of vitamin D in the management of osteoporosis

“…Thus, winter supplementation with vitamin D is needed even after a sunny summer. Furthermore, several studies suggest that many older persons will not achieve optimal serum 25(OH)D levels during the summer months, suggesting that vitamin D supplementation should be independent of the season in older persons [30][31][32].…”

Association between atherosclerosis and osteoporosis, the role of vitamin D

“…In most people, these concentrations cannot be reached with the currently recommended daily intakes of 200 IU and 600 IU Vit D for younger and older adults, respectively. Several studies suggest that many older people will not achieve optimal serum 25(OH)D concentrations during the summer months, which suggests that Vit D supplementation should be independent of season in older persons [68]. An intake for all adults of ≥ 1000 IU (25 µg) Vit D 3 (cholecalciferol)/daily is needed to bring Vit D concentrations up to 75 nmol/l (30 ng/ml) in at least 50% of the population [69].…”