Although there are concerns about long-term prescription of this form of vitamin D, short-term therapy might be a viable strategy, particularly because expression of Cyp27B1, the catalytic enzyme that converts circulating 25(OH)D into active calcitriol (1,25[OH]2D3), is inhibited by glucocorticoids58; treatment of patients with SR asthma with oral calcitriol would bypass this effect. Here, CYP27B1 is linked to asthma.