Age dependence of testosterone precursors in plasma of normal adult males.

Radioimmunoassays for the measurement of pregnenolone, 17alpha-hydroxyprogesterone, androstenedione, dehydroepiandrosterone (DHEA) and androstenediol (5-androstene-3beta, 17beta-diol) have been developed. In addition the reliability criteria of these methods have been established. Age dependence of testosterone precursors in plasma was studied in 80 normal males aged 19 to 93 years. When a young to middle aged group (19-54 years) was compared with an old age group (67-93 years) a highly significant (P less than 0.001) decrease was observed for all the precursors studied: DHEA -68.1%, pregnenolone -60.3%, androstenediol -53.8%, 17alpha-hydroxyprogesterone -47.5% and androstenedione -39.2%.