Bone Mineral Density and Bone Turnover in Asthmatics Treated with Long-Term Inhaled or Oral Glucocorticoids

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Abstract
Inhaled glucocorticoids are pivotal in maintenance therapy of chronic bronchial asthma; however, conflict exists over their effects on bone and mineral metabolism. We measured bone mineral density (BMD), bone turnover markers, and adrenal steroid hormones in 53 patients (34 female, 19 male) with chronic bronchial asthma who had taken either inhaled beclomethasone or budesonide in doses of ≥ 1500 μg/day for at least 12 months to determine pathogenetic mechanisms of bone loss. To account for the effect of prior oral glucocorticoid exposure we divided patients into two groups: one with (OG) and the other without (IG) a past history of maintenance (> 1 month) oral glucocorticoid therapy. Lumbar spine (LS) and proximal femur BMDs were ∼1 SD lower in men and women taking OG or high‐dose IG for chronic bronchial asthma, potentially equivalent to a doubling of the risk of fracture at these sites. Prior exposure to OG in women was also associated with lower LS and proximal femur BMDs, while men were more sensitive to the adverse effects of IG on LS and Ward's triangle BMDs. Bone formation markers were decreased; however, bone resorption marker concentrations were normal. All patients had evidence of suppression of both endogenous glucocorticoid and adrenal androgen production. Both total duration of OG and biochemical bone turnover marker concentrations were negatively related to proximal femur and rib BMDs and total body bone mineral content, but not to LS BMD. These were stronger for bone resorption markers. Uncoupling of ongoing normal bone resorption from suppressed bone formation may therefore contribute to glucocorticoid‐associated bone loss in asthma. Adrenal androgen suppression may also increase the susceptibility of postmenopausal women in particular to bone loss with OG. Although the effects of high‐dose IG on BMD are associated with lower LS BMD in men, this observation should now be investigated further in prospective studies.