[Radioimmunoanalysis of plasma testosterone]

A simple radioimmunoassay procedure for the determination of testosterone concentration in plasma is described. Small amounts of plasma, 0,5 ml for males and 1 ml for females, are extracted with diethyl ether. Recoveries for the extraction are obtained by the addition of labelled tesosterone. The radioimmunoassay is performed directly on the extracts without further purification. Separation of the free from the antibodie bound testosterone is achieved with dextran coated charocoal. Under the used conditions, the calibration curve covers a range between 0,5 and 1,5 ng per sample. Reproducibility is acceptable with a coefficient of variation of 7%. The normal values are slightly higher than those obtained with methods using some purification step of the extract before the assay but due to its simplicity the described method is a suitable one for clinical purposes.