URINARY TESTOSTERONE GLUCURONIDE AS A MEASURE OF ENDOGENOUS TESTOSTERONE PRODUCTION

Abstract

ABSTRACT It is generally assumed that urinary excretion of testosterone glucuronide (TG) represents a relatively constant fraction (about 1 %) of the circulating testosterone which is metabolized. For this urinary TG to be a reliable indicator of testosterone production, the constancy of the fractional conversion of endogenous testosterone to urinary TG must be validated. Small changes in a low fractional conversion would induce large errors in the estimate of endogenous production. Following intravenous injection of [4-14C] testosterone, the per cent of the injected material found in the testosterone glucuronide fraction of a 48 hour urine collection was determined in several groups of subjects. In eight males the value ranged from 0.80 to 2.34%; in ten normal females from 0.26 to 0.84%; and in fifteen hirsute females from 0.05 to 0.80 %, a 16-fold difference. It is concluded that the assessment of endogenous testosterone production from urinary TG is materially influenced by changes in fractional conversion, and this introduces a very large degree of unreliability in the interpretation of urinary TG excretion data.