Premium
Bone Loss in Patients with Untreated Chronic Obstructive Pulmonary Disease Is Mediated by an Increase in Bone Resorption Associated with Hypercapnia
Author(s) -
Dimai Hans P.,
Domej Wolfgang,
Leb Georg,
Lau K.H. William
Publication year - 2001
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.2001.16.11.2132
Subject(s) - medicine , hypercapnia , copd , endocrinology , bone resorption , osteocalcin , bone remodeling , n terminal telopeptide , arterial blood , acidosis , chemistry , biochemistry , alkaline phosphatase , enzyme
Abstract This study sought to determine whether the bone loss in untreated chronic obstructive pulmonary disease (COPD) is associated with hypercapnia and/or respiratory acidosis. Bone mineral density (BMD) measured at the distal forearm of the nondominant arm (with peripheral quantitative computed tomography [pQCT]) and serum markers of bone turnover were determined in 71 male patients with untreated COPD and 40 healthy male subjects who matched the patients in age, weight, and body mass index (BMI). The COPD patients, compared with controls, had reduced pulmonary functions, lower arterial pH, and elevated arterial partial pressure of CO 2 (P CO 2). The BMD (in T score) was significantly lower in COPD patients than that in control subjects (−1.628 ± 0.168 vs. −0.058 ± 0.157; p < 0.001). The BMD of COPD patients correlated positively with arterial pH ( r = 0.582; p < 0.001), negatively with P CO 2( r = −0.442; p < 0.001), and negatively with serum cross‐linked telopeptide of type I collagen (ICTP), a bone resorption marker ( r = −0.444; p < 0.001) but not with serum osteocalcin, a bone formation marker. Serum ICTP, but not osteocalcin, correlated with P CO 2( r = 0.593; p < 0.001) and arterial pH ( r = −0.415; p < 0.001). To assess the role of hypercapnia, COPD patients were divided into the hypercapnic (P CO 2> 45 mm Hg; n = 35) and eucapnic (P CO 2= 35–45 mm Hg) group ( n = 36). Patients with hypercapnia had lower BMD, lower arterial pH, and higher serum ICTP than did patients with eucapnia. Arterial pH and serum ICTP of eucapnic patients were not different from those of controls. To evaluate the role of uncompensated respiratory acidosis, COPD patients with hypercapnia were subdivided into those with compensatory respiratory acidosis (pH ≥ 7.35; n = 20) and those with uncompensated respiratory acidosis (pH < 7.35; n = 15). The BMD and serum ICTP were not different among the two subgroups. In conclusion, this study presents the first associative evidence that the bone loss in COPD is at least in part attributed to an increased bone resorption that is associated primarily with hypercapnia rather than uncompensated respiratory acidosis.