Towards a universally accepted definition of subclinical Cushing's syndrome - subclinical autonomous hypercortisolism

A liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based assay to profile 20 plasma steroids in endocrine disorders

Background

Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based assays are employed in more and more clinical laboratories to quantify steroids. The steroid quantification by LC-MS/MS shows great value in screening or diagnosing endocrine disorders; however, the number of functional steroids included in the LC-MS/MS methods is still limited.

Methods

Here, we describe the performance and validation of a 20-steroid plasma panel by LC-MS/MS. The panel included progestogens (including mineralocorticoids and glucocorticoids), androgens and estrogens biosynthesized in steroid metabolic pathways. The LC-MS/MS method was validated according to guidance documents, and subsequently employed to profile steroid changes in endocrine disorders.

Results

Using LC-MS/MS, 20 steroids were separated and quantified in 8 min. Coefficients of variation (CVs) of the 20 analytes at the lower limit of quantification (LLoQ) were all less than 15% (ranging from 1.84% to 14.96%). The linearity of the assay was demonstrated by all the R2 values greater than 0.995. Individual plasma steroids changed significantly in patients with subclinical Cushing's syndrome (SCS) and polycystic ovary syndrome (PCOS) - 17-hydroxypregnenolone (17-OH-PR), testosterone (T) and dihydrotestosterone (DHT) were significantly decreased in SCS patients, while in PCOS patients, pregnenolone, corticosterone (CORT), androstenedione (A4) and T were significantly increased and DHT was decreased.

Conclusions

The LC-MS/MS method we developed for the quantification of 20 plasma steroids is clinical practicable. The steroid profiling data using this assay indicate its screening value for endocrine disorders. To further explore the value of the assay, more investigations are however needed.

How useful is urinary-free cortisol in the clinic?

Measurement of 24-h urine-free cortisol is frequently employed as a first-line screening and disease-monitoring test in Cushing's syndrome (CS). The quest for ‘cortisol specificity’ has seen the emergence of mass spectrometry (MS) based assays, particularly liquid chromatography/tandem mass spectrometry. In contrast to traditional immunoassays, liquid chromatography/tandem mass spectrometry ‘free cortisol’ measurement is less susceptible to ‘interference’ from cortisol precursors and metabolites. However, detection of these conjugates is important in mild CS and therefore, missed by MS if cortisol alone is measured. MS assays nevertheless are capable of measuring broad steroid profiles, including the potential to distinguish benign from malignant adrenal-based CS and detection of exogenous glucocorticoids. Until this is routine practice, we recommend against abandoning immunoassays measurement of urine-free cortisol.