Influence of high dose inhaled steroids on hypothalamo-pituitary-adrenal axis function in Japanese patients with asthma: a comparison over the course of time.

Although the influence of high dose inhaled steroids on hypothalamo-pituitary-adrenal (HPA) function in patients with asthma has been extensively studied worldwide, there has been limited information on Japanese asthmatics, especially in terms of a prospective analysis of HPA function in the course of time. We analyzed the changes in HPA function using 2 serial short tetracosactrin tests (STT) separated by an interval of one year in 11 Japanese asthmatics who were treated with high dose inhaled steroids alone [beclomethasone dipropionate (BDP); mean dose 982 micrograms/day] during the period between 2 STTs. Mean values of plasma cortisol before administration of ACTH, maximum cortisol and the rise in cortisol in response to ACTH in the 2 STTs were 7.8, 20.5 and 12.7 micrograms/dl for the 1st test, and 8.9, 23.6 and 14.7 micrograms/dl for the 2nd test, respectively. Overall, there was no significant change in the course of time in each of these 3 values. Although the results of the 1st STT proved to be abnormal in 3 patients who had been receiving systemic steroids before their 1st STT, they improved uniformly in their 2nd STT. In the remaining 8 patients, who had never received systemic steroids, 4 patients showed improvements while the other 4 showed deterioration in HPA function in their serial STTs over the course of time. The dose of BDP was 800 micrograms/day in the former 4 patients, while it was 1,200 micrograms/day in the latter 4. Furthermore, only one patient, in whom BDP had been increased from 800 micrograms/day to 1,200 micrograms/day between the 2 tests, developed an abnormal response in the 2nd STT. On the other hand, one patient whose BDP dose was increased from 800 micrograms/day to 1,600 micrograms/day showed an improvement in HPA function in the 2nd test. These results indicate that the threshold dose of BDP which may cause HPA suppression in Japanese asthmatics lies between 800-1,200 micrograms/day, although there is a large inter-individual variation in terms of such doses.