Clinical significance of unconjugated 3 alpha,5 beta-tetrahydroaldosterone and 5 beta-dihydroaldosterone measured by radioimmunoassay.

Radioimmunoassays of two unconjugated reduced metabolites of aldosterone were developed. Excretion rates of unconjugated 5 beta-dihydroaldosterone (5 beta-DHAld) and 3 alpha,5 beta-tetrahydroaldosterone (3 alpha,5 beta-THAld) were measured in 192 hypertensive patients and 16 normal subjects and results were compared with urinary tetrahydroaldosterone-glucuronide(TH-Aldo-glu), aldosterone-18-glucuronide (Aldo-18-glu) and 'free' aldosterone. Generally, values of unconjugated reduced metabolites correlated with one another but in some cases were exceptionally elevated indicating alteration of urinary bacterial flora or impairment of the enzymatic system regulating the conjugation reaction. We suggest that in those cases of hypertension and suspected primary aldosteronism when aldosterone-18-glucuronide and tetrahydroaldosterone glucuronide values remain within normal range, determination of the free metabolite fraction may be diagnostically helpful.