Objective. In an observational long-term study, we followed 62 children (37 males, 25 females; mean age: 11.6 ± 2.9 years) with moderate-to-severe asthma for 2 years and studied the effects of fluticasone propionate (176–1320 μg/day) on the function of the hypothalamic-pituitary-adrenal axis.
Study Design. Morning cortisol levels were monitored after patients had been on fluticasone for a mean of 8.0 ± 5.2 months. Patients who had abnormal low morning cortisol levels (<5.5 μg/dL) were then switched either to lower fluticasone dosage or to other inhaled steroid formulation. Exact methods based on the binomial distribution were used to construct a 95% confidence interval for the true proportion of abnormal readings among those treated, and the Wilcoxon signed rank test was used to test for a significant difference between cortisol levels taken before and after the switch.
Results. Twenty-two patients (36%) had abnormal morning cortisol levels while on fluticasone. Of the patients on a low dose (176 μg/day), 17% had abnormal values, whereas 43% of patients on a high dose (≥880 μg/day) were abnormal. Patients with abnormal results (17/22) had their morning cortisol levels repeated 3 months after the switch. Thirteen of these patients (77%) had normal levels. A stratified analysis of the difference in morning cortisol levels before and after the switch showed significant increase in morning cortisol levels in the group receiving 440 μg/day or less of fluticasone (median difference: 5.25; confidence interval: 3.60–8.15), as well as in the group receiving 440 μg/day or more (median difference: 3.85; confidence interval: 1.00–7.60).
Conclusion. Inhaled fluticasone, even at conventional doses, may have greater effects on the adrenal function than previously recognized, but the clinical significance of this suppression still remains to be established.