Mass Spectrometry in the Diagnosis of Disorders in Steroid Metabolism

It was about 40 years ago, when mass spectrometry (MS) was used for first determinations of steroids in human serum. Meanwhile, technical progress has rendered the development of practicable and clinically applicable methods of steroid determinations based on mass spectrometry possible.

Gas chromatography-mass spectrometry: High-resolution gas chromatography (GC) has the highest potential of all methods for steroid separation and therefore permits multicomponent steroid analysis. Determination of steroids based solely on GC can become problematic because retention time presents the only criterion of identification. The hyphenated technique of GC-MS generates data directly related to the structure of analytes and thus permits highest specificity. The method employed in the authors’ lab allows the simultaneous determination of up to 50 urinary steroid metabolites and allows non-selective and non-invasive diagnosis of most steroid-related disorders. Analysis of 24 h urinary samples permits calculation of excretion rates, assessment of hormonal production rates or monitoring of substitution therapy.

The highly sensitive technique of “selected ion monitoring“ is the prerequisite for the quantitation of low concentrations of plasma steroids. The technique of isotope dilution/GC-MS, which uses stable isotope- labeled internal standards as – almost ideal – internal standards, presents the reference method (gold standard) in steroid analysis. In contrast to immunoassay, our clinical methods for measuring steroids by of isotope dilution GC/MS circumvent problems arising from cross-reactivity or matrix effects.

Liquid chromatography (LC)-mass spectrometry: This technique presents the method of choice in case intact conjugates or complex steroids have to be determined. Techniques like LC-tandem mass spectrometry allow high throughput, but lack the potential of steroid profiling as possible with GC-MS.