Urinary free 11-hydroxycorticosteroid/creatinine ratios in early morning urine samples as an index of adrenal function.

Urinary free 11-hydroxycorticosteroid/creatinine ratios were determined in early morning urine samples from 113 females (age range 20-45 years) and 65 males (age range 22-45 years). Basal values in normal subjects fluctuated between 5 and 55 mumol/mol creatinine. In four patients in whom Cushing's syndrome was diagnosed, urinary free 11-hydroxycorticosteroid/creatinine ratios were greater than 85 mumol/mol creatinine. Administration of dexamethasone (0.5 mg/q.i.d.) to nine normal laboratory staff for two days resulted in a suppression of the urinary free 11-hydroxycorticosteroid/creatinine ratio to less than 50% of the mean basal value in all cases. This degree of suppression did not occur in two cases of Cushing's syndrome due to adrenal tumours.