Indices of gonadal function in the human male. II. Seminal plasma levels of steroids in normal and pathological conditions.

A radioimmunoassay method developed previously for the measurement of unconjugated pregnenolone, dehydroepiandrosterone, androstenedione, testosterone, dihydrotestosterone and oestradiol in peripheral plasma was applied to the assay of these steroids in seminal plasma of normal, oligospermic and azoospermic males. It was not possible to use the plasma assay method for the determination of progesterone and oestrone in seminal plasma, because some of the reliability criteria were not fulfilled. A detailed analysis of these steroids in the peripheral plasma of the same subjects has been described previously. The levels of all steroids in seminal plasma were significantly lower than the corresponding blood levels. The ratios of blood plasma/seminal plasma levels of the various steroids varied from 37 (testosterone) to 1.7 (dihydrotestosterone). There was a positive correlation between the testosterone and dihydrotestosterone levels of the seminal plasma of normal and azoospermic subjects. The concentrations of dihydrotestosterone, pregnenolone and oestradiol were significantly lower in azoospermic subjects than in normals. The only pathological finding in the seminal plasma of oligospermic subjects was a diminished level of dihydrotestosterone. Enzymic hydrolysis of a seminal plasma pool resulted in a 3- to 8-fold increase in the concentration of pregnenolone, dehydroepiandrosterone, testosterone, dihydrotestosterone and oestradiol, indicating that human seminal plasma contains large amounts of steroid conjugates. It is suggested that the analysis of steroids in the seminal plasma in combination with determinations in peripheral plasma may be a valuable aid to the assessment of testicular function.