Adrenal Response to Small Intravenous Doses of Corticotropin in Man

¹ From the Medical Service and Research Laboratory, Veterans Administration Hospital, and the Department of Medicine, Boston University School of Medicine, Boston, Massachusetts

The adrenocortical response to intravenous corticotropin given at a rate of 0.25 mg/hr. for 1–4 hours was studied in six male patients free from acute illness at the time of study. Serial determinations of urinary corticosteroid excretion and of circulating eosinophils were employed as measures of change in adrenocortical activity. Eosinopenia and significant augmentation (P < .01) of urinary excretion of 17-hydroxycorticoids was demonstrable in each subject when the infusion was continued for 2 or more hours (total dose 0.5–1.0 mg). It was found that 10.0 mg of ACTH produced no greater augmentation of 17-hydroxycorticoid excretion during a 3-hour collection period than did 1.0 mg. Other studies have indicated that steroid excretion during more prolonged urine collection periods was greater at the higher dose level. These observations suggest that low and high doses of corticotropin may evoke a similar initial adrenocortical hormone output but that the increase in hormone production after the larger dose is more protracted.