Evening urinary free corticoids: a screening test in Cushing's syndrome and incidentally discovered adrenal tumours.

In this study, we investigated the usefulness of the determination of evening urinary free corticoids/creatinine in samples collected from 20.00 to 24.00 h as a screening test in Cushing's syndrome. In controls (N = 61) the ratio values ranged from 1.1 to 9.4 mumol/mol, whereas in patients with Cushing's syndrome (N = 20), they ranged from 27.5 to 855.5 mumol/mol. However, in 28% of patients with major obesity (greater than 50% overweight) and no hypercortisolism, the ratio values were between 9.4 to 27.8 mumol/mol. A short (10 days) hypocaloric diet induced a decrease in the values in 75% of these patients; the normal range was reached in 50% of them. In addition, the evening urinary free corticoids/creatinine was slightly abnormal in 8 out of 10 patients with incidentally discovered 'silent' adrenal adenomas, whereas it was normal in all 6 with other adrenal masses. In conclusion, evening urinary free corticoids/creatinine is easy to obtain and it reaches a higher sensitivity (100%) and specificity (97%) than the 24 h urinary free corticoids. In the case of borderline values, the presence of overweight should be taken into account.