Endocrine Abstracts

Background: Cystic fibrosis-related bone disease (CFBD) is an emerging complication of cystic fibrosis (CF), especially in CF-lung transplant candidates for end-stage disease.

Objectives: The assessment of vitamin D levels, bone mineral density (BMD) and morphometric and clinical prevalent fragility fractures in a cohort of young adults affected with CF awaiting lung transplantation for end-stage respiratory failure.

Methods: In 42 CF-patients (24 females, age 33.7±8.3 years), who were consecutively referred as lung transplant candidates to our Hospital, we evaluated the parameters of calcium metabolism, including 25-OH vitamin D (25OHVitD) levels, BMD by dual-energy x-ray absorptiometry and vertebral fractures by spinal radiograph.

Results: Mean 25OHVitD levels (22.0±10.4 ng/mL) were below the reference range and hypovitaminosis D (25OHVitD <30 ng/mL) was found in 34 patients (81%) despite vitamin D supplementation in the majority of patients. Even mean daily calcium intakes (615.5±266.8 mg/day) were lower than that recommended (1000 mg/day). BMD FT Z-scores were inversely correlated with prednisone cumulative exposure (r=−0.383, P=0.015) and BMD FN and FT Z-scores were directly correlated with albumin-adjusted calcium (r=0.387, P=0.020 and r=0.346, P=0.039 respectively) and 25OHVitD levels (r=0.508, P=0.001 and r=0.554, P=0.0001 respectively). In particular, no patients with normal 25OHVitD levels showed FT Z-scores <−1.0. A BMD below the expected range for age (Z-score <−2.0) was found in 22 patients (52.4%) and at least one prevalent fracture in 18 patients (45.2%). In patients with a BMD Z-score <−2.0 the prevalence of fragility fractures tended to be higher (59.1%) than in patients with a BMD within the range of age (30.0%, P=0.059), whereas these two groups were comparable as far as age, gender, body mass index, familiar history of fracture, glucocorticoid exposure, daily calcium intake and vitamin D supplementation, prevalence of main CF-related comorbidities, albumin-adjusted calcium and 25OHVitD levels.

Conclusions: Despite the improvement of CF-care, CFBD is still highly prevalent in young adults awaiting lung transplantation for end-stage CF. In order to optimize bone health of CF population approaching lung transplantation, glucocorticoid use should be minimized whenever possible, optimal calcium intake ensured and hypovitaminosis D adequately corrected.