Adrenal responses to a low-dose short synacthen test in children with asthma

Objectives: Corticosteroids are known to cause adrenal suppression. The aim of this study was to assess clinical factors affecting responses to a low dose short synacthen test (LDSST) in asthmatic children using corticosteroids.

Design: Patients were recruited from secondary care paediatric asthma populations within the UK.

Patients: Asthmatic children (5-18 years), receiving corticosteroids, underwent a LDSST (n = 525).

Measurements: Demographics and corticosteroid doses were tested for association with baseline and peak (stimulated) cortisol concentrations.

Results: Baseline cortisol was significantly associated with age (log baseline increased 0·04 nm per year of age, P < 0·0001), but not with gender or corticosteroid dose. Peak cortisol was significantly associated with total corticosteroid cumulative dose (decreased 0·73 nm per 200 mcg/day, P < 0·001) but not with age, gender inhaled/intranasal corticosteroid cumulative dose or number of courses of rescue corticosteroids. Biochemically impaired response (peak cortisol ≤500 nm) occurred in 37·0% (161/435) overall, including children using GINA low (200-500 mcg/day beclomethasone-CFC equivalent 32%, n = 60), medium (501-1000 mcg/day (33%, n = 57) and high (>1000 mcg/day 40%, n = 13) doses of inhaled corticosteroid (ICS) similarly, and 36·6% of those using fluticasone ICS ≥500 mcg/day (71/194). Impaired response was more frequent in patients on regular oral corticosteroids (66%, n = 27, P < 0·001).

Conclusion: Children with asthma can develop biochemical adrenal suppression at similar frequencies for all ICS preparations and doses. The clinical consequence of biochemical suppression needs further study.