Plasma Precursors of Estrogen. I. Extent of Conversion of Plasma Δ4-Androstenedione to Estrone in Normal Males and Nonpregnant Normal, Castrate and Adrenalectomized Females

After the intravenous administration of tracer doses of 4-14C-Δ4-androstenedione +6,7-3H-estrone (or 6,7-3H-estradiol) to normal adult males, and normal, castrate and adrenalectomized young adult females, radioactive urinary metabolites of estrogen were isolated from 72-hr urine collections. In each subject studied a fraction of the administered 4-14C-Δ4-androstenedione was metabolized in the same manner as was the injected tritium labeled estrone. The extent of conversion of 4-14C-Δ4-androstenedione to the product hormone, estrone, was calculated from the relationship between the 3H/14C ratio of the administered tracers and that of the isolated urinary estrone. In the subjects studied an average of 1.3% of Δ4-androstenedione (range 1.0- 1-7 %) was converted to estrone. These results indicate that in the young adult female an “extraglandular” source of estrone of approximately 44 μg/day may arise from plasma borne Δ4-androstenedione. In the adult male, 18 μ of estrone /day can be expected to originate from plasma Δ4-androstenedione.