Low bone mineral density in adults with cystic fibrosis

Abstract

Background-Patients with cystic fibrosis have several risk factors for the development of low bone mineral density (BMD).To identify the prevalence and clinical correlates of low BMD in adult patients with cystic fibrosis, densitometry was performed in 151 patients (83 men) aged 15-52 years. Methods-BMD was measured in the lumbar spine (L1-4) using dual energy x ray absorptiometry (DXA) and quantitative computed tomography (QCT). It was also measured in the proximal femur (total hip and femoral neck) using DXA, and in the distal and ultra distal forearm using single energy x ray absorptiometry (SXA). Biochemical markers of bone turnover, vitamin D levels, parathyroid hormone levels, and a variety of anthropometric variables were also assessed. Conclusions-Low bone density is prevalent in adult patients with cystic fibrosis. Current levels of vitamin D supplementation appear to be inadequate. (Thorax 1999;54:961-967)

Failure of High-Dose Ergocalciferol to Correct Vitamin D Deficiency in Adults with Cystic Fibrosis

“…The exact prevalence depends on the threshold used to define "deficient." Studies using a threshold of less than 15 ng/ml estimate the prevalence of deficiency to be 30 to 40% (5,20). Using a threshold of less than 20 ng/ml results in approximately 50 to 60% being deficient (15).…”

“…With this increase in survival, there has also been growing recognition of health issues unique to the adult population with CF (2). One of these issues is bone health, because studies using dual-energy x-ray absorptiometry measurements of bone density have determined that, despite their young age, approximately 20 to 25% of adults with CF have osteoporosis and another 40% have osteopenia (3)(4)(5). The etiology of this bone disease is multifactorial, with contributors including fat malabsorption (resulting in vitamin D malabsorption and abnormal calcium metabolism) (6)(7)(8), glucocorticoid therapy (9, 10), poor nutritional status (11), inadequate gonadal hormones (10,12), and elevated circulating cytokines (13).…”

“…Recognition of this increased risk of osteoporosis in CF has led to greater efforts to optimize vitamin D status and calcium absorption (4,14). The overall prevalence of vitamin D deficiency in adults with CF is strikingly high, with as many as 50 to 60% having 25-hydroxyvitamin D (25-OHD) levels below 20 ng/ml (5,15). Data demonstrating that serum 25-OHD levels need to exceed 30 ng/ml to prevent a rise in serum parathyroid hormone (16) suggest that the prevalence of vitamin D deficiency in CF may be even higher.…”

Increased NF-κB Activity and Decreased Wnt/β-Catenin Signaling Mediate Reduced Osteoblast Differentiation and Function in ΔF508 Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Mice

“…Several studies indicate that cystic fibrosis mutations may impact the skeleton in children and adults. Most patients with cystic fibrosis display low bone mass associated with fractures (2)(3)(4)(5). The mechanisms underlying this bone pathology are complex and may involve inflammation and altered physical activity and nutritional status (6).…”

“…2 The main function of the CFTR protein is as a chloride channel in epithelia, and the most common mutation in humans, ⌬F508-CFTR, is responsible for a channelopathy in epithelial cells (1). Several studies indicate that cystic fibrosis mutations may impact the skeleton in children and adults.…”