Liquid chromatographic assay of urinary free cortisol

Cortisol in concentrated sulfuric acid forms two major fluorescing compounds which are separated by chromatography on a reversed-phase column. Based on this reaction, urine free cortisol, after double extraction was assayed by high-performance liquid chromatography with fluorescent detection. The method is sensitive, rapid, and free from interferences. The values by this method are 30% lower than radioimmunoassay. In addition to Cushing's syndrome, patients with acute pancreatitis had elevated levels of urinary free cortisol which parallel urinary amylase levels while patients with myocardial infarction had normal levels. Urinary free cortisol showed diurnal variation with elevated values early in the morning.