title: Measurement of estradiol, estrone, and testosterone in postmenopausal human serum by isotope dilution liquid chromatography tandem mass spectrometry without derivatization.
abstract: BACKGROUND
  A high-throughput, sensitive, specific, mass spectrometry-based method for quantitating estrone (E1), estradiol (E2), and testosterone (T) in postmenopausal human serum has been developed for clinical research. The method consumes 100μl human serum for each measurement (triplicates consume 300μl) and does not require derivatization. We adapted a commercially available 96-well plate for sample preparation, extraction, and introduction into the mass spectrometer on a single platform.
  
  
  METHODS
  Steroid extraction from serum samples and mass spectrometer operational parameters were optimized for analysis of estradiol and subsequently applied to other analytes. In addition to determining the limit of detection (LOD) and limit of quantitation (LOQ) from standard curves, a serum LOQ (sLOQ) was determined by addition of known steroid quantities to serum samples. Mass spectrometric method quantitative data were compared to results using a state-of-the-art ELISA (enzyme-linked immunosorbent assay) using stored serum samples from menopausal women.
  
  
  RESULTS
  The LOD, LOQ, sLOQ was (0.1pg, 0.3pg, 1pg/ml) for estrone, (0.3pg, 1pg, 3pg/ml) for estradiol, and (0.3pg, 1pg, 30pg/ml) for testosterone, respectively. Mass spectrometry accurately determined concentrations of E2 that could not be quantified by immunochemical methods. E1 concentrations measured by mass spectrometry were in all cases significantly lower than the ELISA measurements, suggesting immunoreactive contaminants in serum may interfere with ELISA. The testosterone measurements broadly agreed with each other in that both techniques could differentiate between low, medium and high serum levels.
  
  
  CONCLUSIONS
  We have developed and validated a scalable, sensitive assay for trace quantitation of E1, E2 and T in human serum samples in a single assay using sample preparation method and stable isotope dilution mass spectrometry.
authors.affiliation: Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States; Department of Pharmacology, University of Colorado Denver, Aurora, CO, United States.
authors.forename: Kerry M
authors.initials: KM
authors.lastname: Wooding
authors.affiliation: Department of Pharmacology, University of Colorado Denver, Aurora, CO, United States.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Hankin
authors.affiliation: Department of Pharmacology, University of Colorado Denver, Aurora, CO, United States.
authors.forename: Chris A
authors.initials: CA
authors.lastname: Johnson
authors.affiliation: Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Chosich
authors.affiliation: Department of Sample Preparation Products, Biotage, Charlotte, NC, United States.
authors.forename: Sung W
authors.initials: SW
authors.lastname: Baek
authors.affiliation: Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Bradford
authors.affiliation: Department of Pharmacology, University of Colorado Denver, Aurora, CO, United States.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Murphy
authors.affiliation: Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO, United States. Electronic address: nanette.santoro@ucdenver.edu.
authors.forename: Nanette
authors.initials: N
authors.lastname: Santoro
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D002853:Chromatography, Liquid; D004958:Estradiol / Q000097:blood*; D004970:Estrone / Q000097:blood*; D005260:Female; D006801:Humans; D057230:Limit of Detection; D017698:Postmenopause / Q000097:blood*; D053719:Tandem Mass Spectrometry; D013739:Testosterone / Q000097:blood*
chemical_list: D004970:Estrone; D013739:Testosterone; D004958:Estradiol
keywords: Estradiol; Estriol; Estrone; Progesterone; Tandem mass spectrometry; Testosterone