Circulating dihydrotestosterone may not reflect peripheral formation

Abstract

We compared the blood (P(B)(DHT)) and urine (P(U)(DHT)) production rate of dihydrotestosterone (DHT) in normal men and women to determine whether peripheral formation was totally reflected in blood. P(B)(DHT) was similar when measured at both sites in men (674±79 vs. 788±207 SE μg/d); however, P(U)(DHT) was greater than P(B)(DHT) in women (174±55 vs. 55±8 μg/d, P < 0.02). Excretion rates of DHT and 3α-androstanediol (3αdiol) were similar in both sexes, despite major differences in blood levels. However, between sexes large differences were present in 3αdiol glucuronide (3αdiolG) in both plasma and urine. These observations indicate that peripheral (renal) formation of DHT and probably 3αdiol were not accurately determined by measurement of these steroids in blood. The large difference between blood and urine production rates in women suggests an important role of non-testosterone precursors of 5α-reduced steroids. Measurements of 3αdiolG may provide more insight into these peripheral events.