Hypovitaminosis D and 'functional hypoparathyroidism' - the NoNoF (Nottingham Neck of Femur) study

Background: calcium and vitamin D deficiency are common in elderly people and lead to increased bone loss, with an enhanced risk of osteoporotic fractures. Although hip fractures are a serious consequence, few therapeutic measures are given for primary or secondary prevention. A combination of calcium and vitamin D may not be the most effective treatment for all patients. Objective: to investigate the effects of hypovitaminosis D on the calcium-parathyroid hormone endocrine axis, bone mineral density and fracture type, and the optimal role of combination calcium and vitamin D therapy after hip fracture in elderly patients. Design: a population-based, prospective cohort study. Methods: 150 elderly subjects were recruited from the fast-track orthogeriatric rehabilitation ward within 7 days of surgery for hip fracture. This ward accepts people who live at home and are independent in activities of daily living. All subjects had a baseline medical examination, biochemical tests (parathyroid hormone, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D) and were referred for bone densitometry. Results: at 68%, the prevalence of hypovitaminosis D (25-hydroxyvitamin D<30 nmol/l) was high. However, only half the patients had evidence of secondary hyperparathyroidism, the rest having a low to normal level of parathyroid hormone ('functional hypoparathyroidism'). Patients with secondary hyperparathyroidism and hypovitaminosis D had a higher mean corrected calcium, higher 1,25-dihydroxyvitamin D, lower hip bone mineral density and an excess of extracapsular over intracapsular fractures than the 'functional hypoparathyroid' group (P<0.01). Conclusion: there is a high prevalence of hypovitaminosis D in active, elderly people living at home who present with a hip fracture. However, secondary hyperparathyroidism occurs in only half of these patients. This subgroup attempts to maintain calcium homeostasis but does so at the expense of increased bone turnover, leading to amplified hip bone loss and an excess of extracapsular over intracapsular fractures. Combination calcium and vitamin D treatment may be effective in preventing a second hip fracture in these patients, but its role in patients with hypovitaminosis D without secondary hyperparathyroidism and 'vitamin D-replete' subjects needs further evaluation.