Invalidation of a commercially available human 5α-dihydrotestosterone immunoassay (original) (raw)
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Clinical Chemistry, 2008
Background: Recent reports have described inherent problems with androgen immunoassays compared with mass spectrometry analyses. Methods: We developed a method for measuring serum testosterone (T) and 5α-dihydrotestosterone (DHT) simultaneously via liquid–liquid extraction followed by liquid chromatography–tandem mass spectrometry (LC-MS/MS) with positive-mode electrospray ionization. Results: The DHT and T calibrators showed a linear response from 0.069 nmol/L to 34.4 nmol/L and 69.3 nmol/L, respectively. T interference in the DHT assay and vice versa were negligible. Within- and between-run imprecision values were <5% for both analytes. Percent recoveries of T and DHT spiked into samples at concentrations spanning the calibration curve were 100%–113% and 98%–107%, respectively. The lower limit of quantification was 0.069 nmol/L for both steroids. Serum T concentrations measured by LC-MS/MS were different from those obtained by RIA, especially at lower T concentrations. Serum DH...
Dihydrotestosterone: Biochemistry, Physiology and Clinical Implications of Elevated Blood Levels
Endocrine reviews, 2017
This review on dihydrotestosterone (DHT) biochemistry, physiology, and clinical implications of elevated levels in blood clarifies concepts that are important in clinical practice. Benefits associated with lowered serum DHT levels after 5α-reductase inhibitor (5AR-I) therapy in men have contributed to a misconception that circulating DHT levels are an important stimulus for androgenic action in target tissues (e.g., prostate). Yet evidence from clinical studies indicate that intracellular concentrations of androgens (particularly in androgen-sensitive tissues) are essentially independent of circulating levels. To assess the clinical significance of modest elevations in serum DHT and the DHT/T (testosterone) ratio observed in response to common T replacement therapy, a comprehensive review of the published literature was performed to identify relevant data. We examined not only studies where elevated DHT was documented but also those where 5AR-Is were used to suppress DHT. Where appr...
The Journal of Clinical Endocrinology & Metabolism, 2011
Context: Concern exists that androgen treatment might adversely impact prostate health in older men. Dihydrotestosterone (DHT), derived from local conversion of testosterone to DHT by 5α-reductase enzymes, is the principal androgen within the prostate. Exogenous androgens raise serum DHT concentrations, but their effects on the prostate are not clear. Objective: To determine the impact of large increases in serum DHT concentrations on intraprostatic androgen concentrations and androgen action within the prostate. Design: Double-blind, randomized, placebo-controlled. Setting: Single academic medical center. Participants: 31 healthy men ages 35–55. Intervention: Daily transdermal DHT or placebo gel. Main Outcome Measures: Serum and prostate tissue androgen concentrations and prostate epithelial cell gene expression after 4 wk of treatment. Results: Twenty-seven men completed all study procedures. Serum DHT levels increased nearly sevenfold, while testosterone levels decreased in men t...
Estimating the Contribution of the Prostate to Blood Dihydrotestosterone
The Journal of Clinical Endocrinology & Metabolism, 2003
The prostate strongly expresses type 2 5α-reductase, which avidly converts on entry most testosterone (T) to 5α-dihydrotestosterone (DHT). However, the quantitative contribution of the prostate to blood DHT is uncertain. We evaluated prostatic contribution to blood DHT by comparing the blood DHT concentrations in androgen-deficient patients with or without a prostate while they were receiving standard dose of T replacement. Androgen-deficient males (ADM) and female to male (F2M) transsexuals were studied in 2 centers, with both groups receiving either testosterone ester injections (250 mg mixed T esters) every 1 wk (Amsterdam) or 800 mg subdermal T implantation (Sydney). Among 39 Dutch patients, F2M (n = 21) were younger and smaller in physique than ADM (n = 18). One week (±1 d) after an injection, plasma DHT concentrations were 1.6 ± 0.2 (F2M) vs. 1.4 ± 0.2 (ADM) nmol/liter (P = 0.47), but the postinjection time interval to blood sampling was shorter in F2M (5.9 ± 0.4 vs. 7.2 ± 0.3...
The Medical Journal of The Islamic Republic of Iran, 1993
Testosterone was measured using antibodies raised against testosterone II B carboxymethyl ether bovine serum albmin (T-IIB-CME-BSA) and testosterone 3O-carboxymethyl oxime-BSA as immunogen. The antibody produced in this study exhibits minimal cross reactivity with the structurally related steroids specially 5 dihydrotestosterone (5 DHD. This allows to ommit the clean up step and measure testosterone in female serum samples accurately with a high sensitivity, precision, and specificity. The coefficent of variation (CY), standard deviation (SD) and standard error of mean (SE) were all in acceptable ranges. Antibody-bound and free steroids were separated by addition of dextran coated charcoal. The method was applied to a set of clinical samples, the results of which are discussed in this communication. The assay was compared with the available imported kits using 125 I as tracer. The correlation coefficient obtained is calcualted to be r= 0.96, showing that the results obtained by the...