Non-conjugated versus total urinary cortisol in the diagnosis of Cushing's syndrome.

The radioimmunoassay of, urinary cortisol extracted by organic solvent (non-conjugated cortisol) has been used in the diagnosis of hypercortisolism for a long time. With the development of more specific antisera it became possible to measure urinary cortisol without extraction (total urinary cortisol). We compared both methods in the hypercortisolism diagnosis. Basal 24-hour urinary cortisol levels from 43 normal subjects, 53 obese patients and 53 Cushing's syndrome patients were measured. Urinary cortisol levels were not statistically different in normal and obese group in either methods (p > 0.05). There was a significant difference for the Cushing's syndrome group in relation to the normal and obese groups in both methods (p < 0.05). Sensitivity was similar for both methods and a positive correlation was noticed in the three groups. We conclude that both methods are efficient for the diagnosis of hypercortisolism but we suggest that total urinary cortisol should be the first choice to diagnose Cushing's syndrome considering its advantages such as low cost and feasibility.