Hypovitaminosis D and parathyroid hormone response in the elderly: effects on bone turnover and mortality

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Abstract
Objective To investigate whether absence of secondary hyperparathyroidism in the presence of hypovitaminosis D has altered bone turnover, fracture risk and mortality. Design A prospective cohort study. Patients A total of 1280 older men and women living in residential care facilities. Measurements We measured baseline serum 25‐hydroxyvitamin D (25OHD), serum intact PTH, serum amino‐terminal propeptide of type I collagen (PINP) and serum carboxy‐terminal telopeptide of type I collagen (CTX‐I). Deaths and fractures were recorded prospectively. Results Hypovitaminosis D (25OHD < 39 nmol/l) and absence of secondary hyperparathyroidism (PTH > 7·0 pmol/l) in the presence of hypovitaminosis D were common in this sample with a prevalence of 77·5% and 53·3%, respectively. In the presence of hypovitaminosis D, residents showing a hyperparathyroid response (n = 406) had significantly higher serum bone turnover markers than individuals with serum PTH levels ≤ 7·0 pmol/l (termed ‘low vitamin D, normal PTH’, n = 463). After adjusting for risk factors, mortality was significantly higher in the secondary hyperparathyroidism group than in the ‘low vitamin D, normal PTH’ group [hazard ratio (HR) = 1·35, 95% confidence interval (CI) 1·12–1·64; P = 0·002]. All residents with serum PTH levels ≤ 7·0 pmol/l (n = 603) were similar with regard to both bone turnover and mortality, independent of their actual vitamin D status. Conclusion Absence of secondary hyperparathyroidism in the presence of hypovitaminosis D appears to be common in the frail elderly and is associated with longer survival, similar to that observed in vitamin D‐replete elderly subjects.