Steroid hormone assays-a critical review

Abstract

The notable and memorable features of methods for the measurement of steroids in blood until recently were the tedium involved, the technical complexities, the empirical witchcraft and the relatively small number of samples and steroids which could be assayed. However, the introduction of isotopic labelling procedures allowed the rigorous establishment of benchmark normal values for many steroids. At the same time the introduction of the blood clearance rate concept allowed physiological handling processes to be evaluated. Saturation analysis procedures heralded the fifth generation of methodology. Competitive protein binding assays were fragile, full of traps for the unwary, but held the promise that relatively simple methods could be evolved which could handle vast numbers of samples with relatively simple prelilninary clean-up procedures. The present position is that immunoassays utilizing as a key reagent antibodies raised against steroids are in very wide use. Most known steroids and their metabolites can be measured in this way. These procedures, although very suitable for batch processing and automation, still have their problems. Quality control procedures must be rigorous. and although these procedures look easy compared to the older assays, they still require a great deal of skill and protracted concentration spans. Some common pitfalls based on theoretical considerations will be discussed.