Challenges and benefits of endogenous steroid analysis by LC-MS/MS

Quantification of endogenous hormonal steroids and their precursors is essential for diagnosing a wide range of endocrine disorders. Historically, these analyses have been carried out using immunoassay, but such methods are problematic, especially for low-concentration analytes, due to assay interference by other endogenous steroids. MS offers improved specificity over immunoassay and can be highly sensitive. GC-MS, with use of stable isotopically labeled internal standards, is considered the 'gold standard' method for serum steroid analysis. GC-MS is the method of choice for profiling steroid metabolites in urine, but these techniques are not appropriate for routine use in clinical laboratories owing to a need for extensive sample preparation, as well as analytical expertise. LC-MS/MS compares well to GC-MS in terms of accuracy, precision and sensitivity, but allows simplified sample preparation. While most publications have featured only one or a limited number of steroids, we consider that steroid paneling (which we propose as the preferred term for multitargeted steroid analysis) has great potential to enable clinicians to make a definitive diagnosis. It is adaptable for use in a number of matrices, including serum, saliva and dried blood spots. However, LC-MS/MS-based steroid analysis is not straightforward, and understanding the chemical and analytical processes involved is essential for implementation of a robust clinical service. This article discusses specific challenges in the measurement of endogenous steroids using LC-MS/MS, and provides examples of the benefits it offers.