Neurosteroid analysis

In this chapter, we review techniques used for the analysis of neurosteroids and discuss the advantages and disadvantages of each method. Because radioimmunoassay (RIA) procedures are well known, we focus more on the relatively recent mass spectrometric methods used for analyzing neurosteroids and their sulfates. We also discuss some promising methods that permit the detection of low levels of neurosteroids in small samples with a minimum number of sample pretreatment procedures. Lowering the limits of detection will enable a better understanding of the physiological function of neurosteroids and the mechanism(s) for neurosteroid regulation of brain function. Moreover, analyzing low levels of neurosteroids more efficiently will increase the throughput, which is important for clinical analysis. Initially, most neurosteroid analyses were performed by RIA. However, many analyses of neurosteroids are now performed by mass spectrometry. To date, the most sensitive, specific, and accurate method for the simultaneous analysis of several neurosteroids is the method of gas chromatography/electron capture/negative chemical ionization mass spectrometry. This method, with its many variants, is described in detail.