Urinary excretion of androgen metabolites, comparison with excretion of radioactive metabolites after injection of [4-14C]testosterone. Influence of age

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Abstract
The influence of age on the metabolic pattern of [4-14C]testosterone [T] was studied in 20 young and 8 elderly males and compared to the metabolic pattern of endogenous androgens; the latter was also studied in 16 young and 8 elderly women. In both young and elderly males, androsterone and etiocholanolone glucuronide represent 65% of [4-14C]T metabolites; together with their sulfoconjugates and with 5.alpha.- and 5.beta.-androstane-3.alpha.,17.beta.-diol, they represent even > 75% of total urinary metabolites. The 5.alpha./5.beta. ratio of metabolites of [4-14C]T was significantly (P < 0.01) correlated with the 5.alpha./5.beta. ratio of the metabolites of the endogenous adrogens, mainly dehydroepiandrosterone and androstenedione. The 5.alpha./5.beta. ratio of [4-14C]T metabolites was generally higher than the ratio of metabolites of endogenous androgens; apparently, the transformation of T to ring A saturated metabolites occurs at least partially in another compartment than the transformation of dehydroepiandrosterone to these metabolites. For both [4-14C]testosterone and endogenous androgen metabolites, a statistically significant reduction of the 5.alpha./5.beta. ratio with age, a general phenomenon in both males and females was observed. This reduction also concerns 11-OH-androst-4-ene-3,17-dione metabolism. Neither sex hormone levels, nor specific binding seems to determine this age dependent shift; neither is there convincing evidence for latent hypothyroidism of liver dysfunction in the elderly. An age associated primary decrease of the 5.alpha.-reductase activity seems the most likely explanation.

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