Plasma Corticosteroids in Normal Individuals: With Reference to the Orcadian Rhythm, ACTH Test, Insulin Test, and Dexamethasone Suppression Test

Fluorimetrically determined plasma corticosteroids were studied in normal individuals. In female subjects the 7 a.m. mean baseline values were significantly higher than those in the male subjects. The adrenal response during the 4-hour ACTH test was significantly higher in female controls than in the male. During insulin test (0.10 i.u./kg) the maximum increase in plasma corticosteroids was 10.7 (3.7-22.8) μg/100 ml (mean and range). No difference in response was observed between male and female controls. During the 1 mg dexamethasone test plasma corticosteroids were suppressed to 2.7 (1.4-4.4) μg/100 ml (mean and range); serum corticotrophin was also significantly suppressed.