Plasma Precursors of Estrogen. II. Correlation of the Extent of Conversion of Plasma Androstenedione to Estrone with Age1

The purpose of the present study was to ascertain the relationship between aging and the extent of conversion of plasma androstenedione to estrone. Studies were carried out in 23 women and 26 men who weighed 130–180 pounds and 150–190 pounds, respectively, in which 3H estrone and 14C-androstenedione were administered intravenously and the transfer constant of plasma androstenedione to estrone as measured in urine, [ρ]AE1/BU, was determined. The results of these studies in both women and men demonstrate that with advancing age, there is a progressive and highly statistically significant increase in the efficiency with which circulating androstenedione is converted to estrone. The magnitude of the increase observed in the older subjects reached 2- to 4-fold that observed in the young adult.