Cortisol production rate determined by radio gas chromatography

Abstract

The authors describe a radio gas chromatographic method for determination of cortisol production rate by measuring the isotope dilution of urinary cortisol metabolites. The method was calibrated by analyzing [3H]tetrahydrocortisol and [3H]tetrahydrocortisone of known specific activities. Results are reasonably well reproducible, the coefficients of variation ranging from 8-15% for allotetrahydrocortisol/tetrahydrocortisol and from 9-16% for tetrahydrocortisone. Correlation coefficients were 0.966 and 0.998 for tetrahydrocortisone and allotetrahydrocortisol/tetrahydrocortisol, respectively, when the method was compared with a method involving thin layer chromatography and colorimetry. Only one chromatographic step is needed for both purification and quantitation, thus time and effort are saved.