title: Ultra-high sensitivity analysis of estrogens for special populations in serum and plasma by liquid chromatography-mass spectrometry: Assay considerations and suggested practices.
abstract: Estrogen measurements play an important role in the clinical evaluation of many endocrine disorders as well as in research on the role of hormones in human biology and disease. It remains an analytical challenge to quantify estrogens and their metabolites in specimens from special populations including older men, children, postmenopausal women and women receiving aromatase inhibitors. Historically, immunoassays have been used for measuring estrogens and their metabolites in biological samples for risk assessment. However, the lack of specificity and accuracy of immunoassay-based methods has caused significant problems when interpreting data generated from epidemiological studies and across different laboratories. Stable isotope dilution (SID) methodology coupled with liquid chromatography-selected reaction monitoring-mass spectrometry (LC-SRM/MS) is now accepted as the 'gold-standard' to quantify estrogens and their metabolites in serum and plasma due to improved specificity, high accuracy, and the ability to monitor multiple estrogens when compared with immunoassays. Ultra-high sensitivity can be obtained with pre-ionized derivatives when using triple quadruple mass spectrometers in the selected reaction monitoring (SRM) mode coupled with nanoflow LC. In this review, we have examined the special issues related to utilizing ultra-high sensitivity SID LC-SRM/MS-based methodology to accurately quantify estrogens and their metabolites in the serum and plasma from populations with low estrogen levels. The major issues that are discussed include: sample preparation for both unconjugated and conjugated estrogens, derivatization, chromatographic separation, matrix effects, and assay validation.
authors.affiliation: Center of Excellence in Environmental Toxicology and Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, United States; Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, United States; Department of Pharmacology and Toxicology, Beijing Institute of Radiation Medicine, Beijing 100850, China.
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Center of Excellence in Environmental Toxicology and Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, United States; Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, United States.
authors.forename: Clementina
authors.initials: C
authors.lastname: Mesaros
authors.affiliation: Center of Excellence in Environmental Toxicology and Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, United States; Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, United States. Electronic address: ianblair@mail.med.upenn.edu.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Blair
mesh_terms: D047072:Aromatase Inhibitors / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy; D002853:Chromatography, Liquid / Q000379:methods*; D004967:Estrogens / Q000032:analysis / Q000097:blood* / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D017698:Postmenopause; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D047072:Aromatase Inhibitors; D004967:Estrogens
keywords: Children; Derivatization; Estrogens and their metabolites; Liquid chromatograph–tandem mass spectrometry; Older men; Postmenopausal women; Stable isotope dilution methodology