Measurement of urinary androgen sulfates without previous hydrolysis: a tool to investigate adrenarche. Validation of a commercial radioimmunoassay for dehydroepiandrosterone sulfate

Abstract

A commercial 125l radioimmunoassay designed for the quantification of dehydroepiandrosterone sulfate (DHEAS) in blood samples was tested for its direct applicability to 24-hour urine samples from children and adults. Average recoveries in parallelism and spiking experiments were found to be near 100%. Intra- and inter-assay coefficients of variation were below 10%. Urinary DHEAS concentrations determined directly by the radioimmunoassay (x) differed only slightly from corresponding radioimmmunoassay values (y) obtained after C 18 reversed-phase extraction and LH-20 chromatography ( y= 0.85 x+0.12; r = 0.99). Cross-reactivity data from related steroids suggested only a small contribution to the DHEAS titer by other steroids. In 8-year-old children compared to preadrenarchal children (4 years old) a clearly increased median daily urinary DHEAS output could be observed both for absolute excretion data (0.163 versus 0.05 μmn//d, P < 0.01) and for excretion values related to body surface area (0.181 versus 0.071 μmol/d/1.73 m 2, P < 0.05). However, this “onset of adrenarche” was no longer statistically significant when urinary creatinine was taken as adjustment parameter for renal androgen sulfate output. After correction with the individual body surface area, rises of urinary DHEAS from childhood to adulthood were nearly in the order of the literature data on age-corresponding serum increases of DHEAS. In conclusion, the direct radioimmunological quantification of DHEAS in 24-hour urine samples with subsequent correction for individual body surface area appears to present a physiologically meaningful way to assess the adrenal gland's secretory activity for this adrogen sulfate.