[Stability of steroids in plasma over a 10-year period].

In order to examine whether plasma samples may be used for steroid analysis after long periods of storage, cortisol, testosterone, oestrone and oestradiol were remeasured in samples, which had been analysed 1.3-10.8 years earlier. The method for the measurement of these steroids was unchanged over this period. The results demonstrate that at a temperature of -25 degrees C steroids remained stable. Only cortisol and testosterone concentrations showed a small, insignificant decrease (6-9%) after 3 to 4 years of storage. These differences are well within the range of the precision of the method (interassay variation), which over a period of 11 years was 9.4%, 8.0%, 10.0% and 9.5% for cortisol, testosterone, oestrone and oestradiol, respectively. It is concluded that steroid hormones in human plasma are stable in our laboratory, and that they might be analysed even after more than 10 years of storage at -25 degrees C.