RADIOIMMUNOASSAY OF TETRAHYDROCORTICOSTERONE (THB) IN HUMAN URINE

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Abstract
Antisera against tetrahydrocorticosterone (THB) (one of the metabolites of the glucocorticoid corticosterone) were raised in white New Zealand rabbits. A 3α,5β-THB-20-oxime-bovine serum albumin complex was used as antigen. The resulting titers were 1/300–1/19 000. The cross-reactions of the best antiserum were: THDOC 2.25%, THB-21-glucuronide 39%, and THF-21-glucuronide 4.8%. Other steroids and steroid metabolites have given negligible cross-reactions, e. g. allo-(3α,5α-)-THB 0.53 %, tetrahydro-11-dehydro-corticosterone (THA) 0.92%, allo-THA 0%, and THB-3-glucuronide 0 %. Two methods were introduced: a) for screening an estimation of THB-glucuronide, mostly THB-21-glucuronide ("THB-gluc."), in unprocessed urine after simple dilution b) specific estimation of THB using one paper chromatographic system. The values estimated by method a) showed a highly significant correlation (r = 0.9654, P < 0.01) with the values obtained by technique b). Normal values (method b) measured in subjects hospitalized under standardized conditions were: 21.8–177.6; mean 89.1 μg/24 h. THB levels and "THB-gluc." levels react to ACTH stimulation and dexamethasone suppression and thus we propose that the methods are useful for the diagnosis of hyper- and hypocorticosterone production states.