Hypovitaminosis D and Low Bone Mineral Density in Inflammatory Bowel Disease Patients

Abstract

Background: Increasing evidences suggest that hypovitaminosis D can play an important role in immuno-mediated diseases, such as Inflammatory Bowel Diseases (IBD). The hypovitaminosis D is an established risk factor for the development of osteopenia, osteoporosis and pathological fractures. Studies have reported a correlation between hypovitaminosis D, disease history and clinical features in Crohn's Disease (CD) and Ulcerative Colitis (UC). The aim of this study is to evaluate the vitamin D serum levels and the prevalence of bone mineral density (BMD) alterations in a population of Italian IBD patients and to correlate the prevalence of hypovitaminosis D with disease history and clinical features. Method: Between October 2013 and November 2014 we enrolled patients from our center that were affected by UC or CD. Exclusion criteria were age below 18 and over 60, concomitant vitamin D replacement therapy and concomitant gastrointestinal or endocrinological diseases which may alter vitamin D metabolism. All patients underwent 25-OH-vitamin D, ESR, C-reactive protein (CRP), PTH, serum calcium and phosphorus, β-CTX, alkaline phosphatase (bone isoenzyme) plasma assay and bone mass density (BMD) evaluation by lumbar and femoral dual-energy X-ray absorptiometry (DXA) scan. Both measurements were made at the same time, during the autumn and winter months. Following 2012 Osteoporosis Italian Society Guidelines, we defined as hypovitaminosis D plasmatic values <30 ng/mL, vitamin D levels were considered as insufficient if between 20 and 30 ng/ mL and deficient if <20 ng/mL. We collected data regarding patients’ life habits and clinical history, disease course and disease clinical activity at enrollment. For BMD evaluation T-score and/or Z-score were calculated for each patient at lumbar (L1-L4) and femoral neck level, and the diagnosis of osteopenia or osteoporosis was made according to international guidelines. Results: We enrolled 88 patients (62 CD, 26 UC); median age at enrollment was 42 years for CD and 43 years for UC. Mean Body Mass Index (BMI) was 22.6 in CD and 23.7 in UC patients. Age at diagnosis was 29.8 years for CD and 33.5 years for UC, with mean disease duration of 12.8 years for CD and 9.1 years for UC.Hypovitaminosis D was observed in 84.1% of the patients. Of these, 31.8% had insufficient vitamin D levels, whereas 57.3% deficient. Mean vitamin D level was 20.4 ng/mL, but there was no difference with respect to sex or disease type. Indeed, there was no correlation between hypovitaminosis D and disease duration or patients age at diagnosis. A statistically significant correlation was found between hypovitaminosis D and history of steroid-dependancy (p=0.03), need of therapy with anti- TNF-α drugs (p=0.01) and cigarette smoke habit in CD patients (p=0.01). In CD patients we also found a correlation, at the limit of statistical significance (p=0.05), between hypovitaminosis D, high CRP values and HarveyBradshaw Index (HBI) at enrollment.70 patients underwent the lumbar DXA analysis, 67 the femoral DXA. Lumbar BMD was found to be below the normal range in 37.1% of the patients, suggesting that 24.2% and 12.9% were affected by osteopenia or osteoporosis, irrespective of sex and disease type (CD or UC). Similarly, femoral BMD was below the normal range for age in 43.3% of the patients. This figure is consistent with osteopenia or osteoporosis in 34.3% and 9%, irrespective of sex and disease type and femoral Z-score that was found significantly lower in CD than UC patients (p=0.03). Reduced BMD correlated with lower BMI and hypovitaminosis D. Conclusion: In our study we found a high prevalence of hypovitaminosis D in an IBD population irrespective of patients' sex, type and duration of disease. Our data show a strong correlation between hypovitaminosis D and a more aggressive disease course in terms of history of steroiddependancy, need of therapy with anti TNF-α drugs and smoke habit in CD patients. Hypovitaminosis D may play a crucial role in causing a more severe clinical behavior of IBD. Alteration of bone metabolism is a concern in IBD patients. We observed a high prevalence of BMD alterations in both men and women affected by UC and CD, even if of young age and with a short disease duration, irrespective of the type of IBD. Such patients may be prescribed lumbar and femoral, especially in cases of hypovitaminosis D and low BMI. This would allow an early diagnosis of BMD alterations, to start specific therapy and to prevent further complications.