In VivoConversion of Dehydroisoandrosterone to Plasma Androstenedione and Testosterone in Man¹

The peripheral conversion of dehydroisoandrosterone (D) to plasma androstenedione (A) and testosterone (T) was studied by constant infusion of labeled D and isolation of both precursor and product steroid from plasma. The metabolic clearance rate (MCRd) of D in 8 normal subjects was 1640 ± 93 (se) liters/day. The transfer constant , the proportion of D converted to A as measured in plasma, was 6.2 %. The transfer constant , the proportion of D converted to T in plasma, was only 0.7%. The product of the MCRd and available values for plasma D concentration indicates a plasma production rate of 7 mg/day. From the production rate and transfer constants it can be calculated that D is a minimal peripheral precursor of both plasma A and T in the normal adult female. In abnormal states of virilization with normal or moderate increases in D production, the increased plasma A and T in these states are not due to peripheral conversion of D in blood. The experimentally determined value of 0.7 % is in reasonable agreement with calculations using the values of and and the conversion to and extraction of T from D in the liver.