Analysis of estrogens and androgens in postmenopausal serum and plasma by liquid chromatography-mass spectrometry

Advances and challenges in liquid chromatography-spectrometry (LC-MS) methodology for quantifying androgens and estrogens in human serum and plasma

Accurate quantification of androgens and estrogens is critical for elucidating their roles in endocrine disorders and advancing research on their functions in human biology and pathophysiology. This review highlights recent advances and ongoing challenges in liquid chromatography- mass spectrometry (LC- MS) methodology for quantifying androgens and estrogens in human serum and plasma. We summarized current approaches for analyzing the different forms of androgens and estrogens, along with their reported levels in publications from 2010 to the present. These published levels pointed out the inconsistencies in reference intervals across studies. To address these issues, advances in derivatization methods and chromatographic separation techniques are reviewed. Future perspectives for improving the accuracy and consistency of hormone quantification in clinical and research settings were also proposed.

Effects of injectable contraception with depot medroxyprogesterone acetate or norethisterone enanthate on estradiol levels and menstrual, psychological and behavioral measures relevant to HIV risk: The WHICH randomized trial

BACKGROUND

Observational data suggest lower HIV risk with norethisterone enanthate (NET-EN) than with depo-medroxyprogesterone acetate intramuscular (DMPA-IM) injectable contraceptives. If confirmed, a switch between these similar injectable methods would be programmatically feasible and could impact the trajectory of the HIV epidemic. We aimed in this paper to investigate the effects of DMPA-IM and NET-EN on estradiol levels, measures of depression and sexual activity and menstrual effects, relevant to HIV risk; and to ascertain whether these measures are associated with estradiol levels.

METHODS

This open-label trial conducted at two sites in South Africa from 5 November 2018 to 30 November 2019, randomized HIV-negative women aged 18-40 to DMPA-IM 150 mg intramuscular 12-weekly (n = 262) or NET-EN 200 mg intramuscular 8-weekly (n = 259). Data were collected on hormonal, behavioral and menstrual effects at baseline and at 25 weeks (25W).

RESULTS

At 25W, median 17β estradiol levels were substantially lower than at baseline (p<0.001) for both methods: 76.5 pmol/L (interquartile range (IQR) 54.1 to 104.2) in the DMPA-IM group (n = 222), and 69.8 pmol/L (IQR: 55.1 to 89.3) in the NET-EN group (n = 225), with no statistical difference between the two methods (p = 0.450). Compared with DMPA-IM, NET-EN users reported significantly less amenorrhoea, fewer sexual acts, fewer users reporting at least one act of unprotected sex, more condom use with steady partner, more days with urge for sexual intercourse, more days feeling partner does not love her, and more days feeling sad for no reason. We did not find a clear association between estradiol levels and sexual behavior, depression and menstrual effects. Behavioral outcomes suggest less sexual exposure with NET-EN than DMPA-IM. The strength of this evidence is high due to the randomized study design and the consistency of results across the outcomes measured.

CONCLUSIONS

Estradiol levels were reduced to postmenopausal levels by both methods. Secondary outcomes suggesting less sexual exposure with NET-EN are consistent with reported observational evidence of less HIV risk with NET-EN. A randomized trial powered for HIV acquisition is feasible and needed to answer this important question.

TRIAL REGISTRATION

PACTR 202009758229976.

Derivatization procedure of estradiol with a combination of MPDNP-F and 4-dimethylaminopyridine to generate product ion containing estradiol-skeleton for reliable determination of its serum/plasma concentrations by LC/ESI-MS/MS

The quantification of serum/plasma estradiol (E2) is useful for the diagnosis, pathological analysis, and monitoring of the therapeutic efficacy of estrogen-dependent diseases. In this study, an improved derivatization method using 1-(2,4-dinitro-5-fluorophenyl)-4,4-dimethylpiperazinium iodide (MPDNP-F) was developed and combined with liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) for the sensitive and specific quantification of the serum/plasma E2. In the new method, the reaction time was reduced to 15 min from 90 min (two-step reaction in the previous method) by the direct reaction of MPDNP-F with E2 at 60°C in the presence of 4-dimethylaminopyridine (DMAP). DMAP served as the organic catalyst and had a less negative effect on the LC/ESI-MS/MS instrument compared to the non-volatile inorganic salt (NaHCO3), which was used in the previous method. The collision-induced dissociation of the molecular cation ([M]+) of the resulting derivative provided a product ion containing the E2-skeleton ([M-NO2-H]+), which significantly enhanced the assay sensitivity and specificity; compared to the dansyl chloride derivatization, which is the currently most-used derivatization procedure for the LC/ESI-MS/MS assays of E2, the MPDNP-F derivatization had significantly fewer interfering peaks and a clear and flat baseline in the serum sample analysis. The MPDNP-F derivatization-LC/ESI-MS/MS method enabled the precise and accurate quantification of E2 even at a 5.0 pg/mL concentration (lower limit of quantification) with a small sample volume (100 μL of serum/plasma) and had a tolerance for the matrix effect. This method was also proven to serve as a more sensitive and specific alternative to the clinically used chemiluminescence enzyme immunoassay.

Concentrations of endogenous sex steroid hormones and SHBG in healthy postmenopausal women

Studies reporting age-specific reference ranges of endogenous sex steroid hormones in postmenopausal women are relatively scarce. If levels differ by age, dosing and treatment regimens should vary among postmenopausal women accordingly. Our objective was to establish reference ranges for sex steroid hormones and sex hormone binding globulin (SHBG) by age group and overall, and to investigate their association with demographic characteristics. Serum samples were obtained from 1207 healthy postmenopausal women aged 41-92, not using hormone therapy, at the baseline visit of 3 clinical trials. Estrone (E1), estradiol (E2), and total testosterone (T) were measured by radioimmunoassay with preceding purification steps; SHBG was measured by direct chemiluminescent immunoassay. Free T (FT) was calculated. Women were categorized by 5-year age groups. There was little change in the mean estrogen levels among the different age groups (E2: 9-12 pg/mL; E1: 33-35 pg/mL). Mean total T levels increased gradually with age from 19.9-26.2 ng/dL, but FT mean levels were relatively constant (3.7-4.6 pg/mL). Mean SHBG levels increased with age from 43-68 nmol/L. A generalized linear model tested the association of each demographic characteristic with the hormones and SHBG. A significant association was derived. Our study provides valuable insight into the profiles of serum sex steroid hormones and SHBG in different healthy postmenopausal women aged 41-92 years.

Quantitative analysis of specific androgens in serum and urine samples from male, pre, and postmenopausal subjects using LC-MRM-MS

Androgens are endogenous hormones that play a crucial role in the paracrine and intracrine hormone system to perform and maintain vital physiological functions. Altered levels of androgens are implicated in many diseases such as sexual dysregulation, breast cancer, prostate cancer, and heart diseases etc. In this manuscript we describe a liquid chromatography-mass spectrometry (LC-MS) method using multiple reaction monitoring (MRM) for quantitatively measuring specific androgens such as dehydroepiandrosterone, testosterone, androsterone sulphate, androstenedione, and dihydrotestosterone in serum and urine samples. Serum acquired from nine different subjects (three pre-menopausal women, three postmenopausal women, and three healthy males) were used to evaluate the developed methods. In the sample preparation methods for serum either protein precipitation or liquid-liquid extraction (LLE) was used while the analysis of urinary androgens used LLE. The extracted androgens were quantitatively measured using LC-MRM-MS to which known amounts of stable isotope labeled standards were added. This manuscript also presents a LC-MRM-MS method mode for the analysis of oxime derivatized androgens potentially to enhance the sensitivity of the assay if required, from urine and venous-drawn serum samples.

LC-HRMS of derivatized urinary estrogens and estrogen metabolites in postmenopausal women

In order to undertake an epidemiologic study relating levels of parent estrogens (estrone and estradiol) and estrogen metabolites (EMs) to other breast cancer risk factors, we have optimized methods for EM quantification with ultra high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). A two-step approach was adopted; the first step comprised method development and evaluation of the method performance. The second step consisted of applying this method to quantify estrogens in postmenopausal women and determine if the observed patterns are consistent with the existing literature and prior knowledge of estrogen metabolism. First, 1-methylimidazole-2-sulfonyl chloride (MIS) was used to derivatize endogenous estrogens and estrogen metabolites in urine from study participants. Since C18 reversed phase columns have not been able to separate all the structurally related EMs, we used a C18-pentafluorophenyl (PFP) column. The parent estrogens and EMs were baseline resolved with distinct retention times on this C18-PFP column using a 30 min gradient. This method was used to quantify the parent estrogens and 13 EMs in urine samples collected in an initial pilot study involving males as well as pre- and peri-menopausal females to assess a range of EM levels in urine samples and enable comparison to the previous literature for assay evaluation. Detection limits ranged from 1 - 20 pg/mL depending on the EM. We evaluated matrix effects and interference as well as the intra- and inter-batch reproducibility including hydrolysis, extraction, derivatization and LC-MS analysis using charcoal-stripped human urine as a matrix. Methods were then applied to the measurement of estrogens in urine samples from 169 postmenopausal women enrolled in an epidemiological study to examine relationships between breast cancer risk, the intestinal microbiome, and urinary EMs. The results from our cohort are comparable to previous reports on urinary EMs in postmenopausal women and enabled thorough evaluation of the method.

Association of serum androgens and coronary artery calcium scores in women

OBJECTIVE

To determine the association between serum androgens measured by high-resolution liquid chromatography-mass spectrometry and coronary artery calcium (CAC) scores.

DESIGN

Cross-sectional study.

SETTING

Academic institution.

PATIENT(S)

A total of 239 women, aged 40-75 years, with CAC testing and complete cardiovascular disease risk evaluation. Total T, DHEA, and androstenedione were measured using high-resolution liquid chromatography-mass spectrometry, whereas E₂ and sex hormone-binding globulin were measured using commercial assays.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Independent associations between CAC scores and sex steroids.

RESULT(S)

Overall, 164 subjects had a CAC score < 10, 48 had a CAC score between 10 and 100, and 27 had a score > 100. There were no differences in sex hormone levels between women with CAC scores > 10 vs. CAC scores ≤ 10. In multivariable models adjusting for age, body mass index, and low-density lipoprotein cholesterol, a higher T/E₂ ratio was associated with an elevated CAC score, with an unadjusted odds ratio associated with 1-SD change in log-transformed T/E₂ of 1.38 (95% confidence interval 1.01-1.89) and adjusted OR 1.02 (95% confidence interval 1.002-1.04). Total T, DHEA, androstenedione, sex hormone-binding globulin, and E₂ levels were not associated with increased CAC.

CONCLUSION(S)

In the general population, there are mixed reports regarding the relationship between serum androgens and risk factors for cardiovascular disease, and limited information on the relationship between androgens and subclinical atherosclerosis. Our study shows that increased androgens relative to estrogens may have a weak but independent association with subclinical atherosclerosis, as measured by CAC scores.

Application of 3D-printed scabbard-like sorbent for sample preparation in bioanalysis expanded to 96-wellplate high-throughput format

Modern bioanalysis, which involves the quantitative and qualitative determination of small-molecule endogenous and exogenous substances in biological samples, is a powerful and useful tool that can generate valuable information related to many areas connected with human health and quality of life. Although LC-MS and GC-MS are widely viewed as the gold standards for many bioanalytical tasks, the scientific community has not abandoned its search for newer, more efficient, and more inexpensive methods of performing extraction as a sample preparation step before final analysis. Recent research showing the immense potential of 3D printing compelled our group to explore how this technology could be applied to techniques used in analytical chemistry. In particular, 3D printing offers three promising advantages: availability, low cost of materials and equipment, and the ability to fabricate objects of nearly any shape to suit the needs of a given application. Previously, we demonstrated that a commercial 3D material (LAY-FOMM) can function as a chemically active object that enables the reversible sorption of the antidiabetic drug, glimepiride, and endogenous steroids. In this report, we use a 3D printer to fabricate sorbents with a scabbard-like shape for use with a 96-blade system, which, along with the use of a 96-well plate, allows multiple extractions to be performed simultaneously. In order to assess the relative benefits of this 3D printed approach, we compare the performance of the proposed LAY-FOMM-based sorbent to that of the widely used C18 sorbent. Although the LAY-FOMM sorbent showed lower extraction recovery rates than the C18 sorbent, all of the other validation parameters suggest that it is suitable for use in high-throughput analysis of steroids in human plasma.

Steroids in Stroke with Special Reference to Progesterone

Both sex and steroid hormones are important to consider in human ischemic stroke and its experimental models. Stroke initiates a cascade of changes that lead to neural cell death, but also activates endogenous protective processes that counter the deleterious consequences of ischemia. Steroids may be part of these cerebroprotective processes. One option to provide cerebroprotection is to reinforce these intrinsic protective mechanisms. In the current review, we first summarize studies describing sex differences and the influence of steroid hormones in stroke. We then present and discuss our recent results concerning differential changes in endogenous steroid levels in the brains of male and female mice and the importance of progesterone receptors (PR) during the early phase after stroke. In the third part, we give an overview of experimental studies, including ours, that provide evidence for the pleiotropic beneficial effects of progesterone and its promising cerebroprotective potential in stroke. We also highlight the key role of PR signaling as well as potential additional mechanisms by which progesterone may provide cerebroprotection.

Derivatization enhances analysis of estrogens and their bioactive metabolites in human plasma by liquid chromatography tandem mass spectrometry

Estrogens regulate many diverse biological processes in health and disease. They circulate at a wide range of concentrations in females generating several active metabolites (hydroxy and methoxyestrogens). The metabolites are assumed to be present in much lower levels and are thought to contribute to diseases such as pulmonary arterial hypertension (PAH). Estrogen metabolites are challenging to quantify in plasma and currently available immunoassays are non-specific. Here we have developed and validated a novel assay to simultaneously quantify parent estrogens and their metabolites by mass spectrometry (MS). Estrogens were extracted from human plasma using solid phase extraction and derivatized using 1-(5-fluoro-2, 4-dinitrophenyl)-4-methylpiperazine (PPZ) before quaternization by methylation ("MPPZ"). MPPZ derivatives were separated and quantified by liquid chromatography tandem MS (LC-MS/MS) in positive electrospray ionization mode, using a QTrap 6500 + coupled to a Shimadzu Nexera X2. Separation was achieved using an ACE Excel 2 C18-PFP column (2 μm, 2.1 mm × 150 mm). The limits of quantification (LOQ) were 0.43-2.17 pg on column with a linear range from 2 or 10 - 2000 pg mL-1. Intra and inter-day precision and accuracy were acceptable (<20% at LOQ and <15% above). These derivatives demonstrated minimal degradation upon short-term storage at 15 °C (<20%) and longer term at -20 °C (<20%). Using this approach, estrone (E1) and estradiol (E2) were detected in plasma (0.5 mL) from healthy women and those with PAH but downstream metabolites 16-hydroxy-E1, 16-hydroxy-E2, 2-methoxy-E1 and 4-methoxy-E1 were only detected in plasma from diseased patients. These findings will next be tested robustly in large patient cohorts. This novel LC-MS/MS analysis of estrogens and their bioactive metabolites, using MPPZ derivatization, opens doors for the simultaneous analysis of a panel of estrogens in human plasma, across the endogenous range of concentrations encountered in health and disease.

Randomized phase II study of fulvestrant and erlotinib compared with erlotinib alone in patients with advanced or metastatic non-small cell lung cancer

OBJECTIVES

This open-label, randomized phase II trial evaluated antitumor efficacy of an antiestrogen, fulvestrant, in combination with human epidermal growth factor receptor (EGFR) inhibitor, erlotinib, in advanced non-small cell lung cancer (NSCLC) patients.

MATERIALS AND METHODS

Patients with advanced or metastatic NSCLC, ECOG 0-2, previous chemotherapy unless patient refusal, and no prior EGFR-directed therapy were randomized 2:1 to erlotinib 150 mg oral daily plus 500 mg intramuscular fulvestrant on day 1, 15, 29 and every 28 days thereafter or erlotinib alone 150 mg oral daily. The primary end point was objective response rate (ORR); secondary endpoints included progression free survival (PFS) and overall survival (OS).

RESULTS

Among 106 randomized patients, 100 received at least one dose of study drug. ORR was 16.4% (11 of 67 patients) for the combination versus 12.1% (4 of 33 patients) for erlotinib (p = 0.77). PFS median 3.5 versus 1.9 months [HR = 0.86, 95% CI (0.52-1.43), p = 0.29] and OS median 9.5 versus 5.8 months [HR = 0.92, 95% CI (0.57-1.48), p = 0.74] numerically favored the combination. In an unplanned subset analysis, among EGFR wild type patients (n = 51), but not EGFR mutant patients (n = 17), median PFS was 3.5 versus 1.7 months [HR = 0.35, 95% CI (0.14-0.86), p = 0.02] and OS was 6.2 versus 5.2 months [HR = 0.72, 95% CI (0.35-1.48), p = 0.37] for combined therapy versus erlotinib, respectively. Notably, EGFR WT patients were more likely to be hormone receptor-positive (either estrogen receptor α- and/or progesterone receptor-positive) compared to EGFR mutant patients (50% versus 9.1%, respectively) (p = 0.03). Treatment was well tolerated with predominant grade 1-2 dermatologic and gastrointestinal adverse effects.

CONCLUSION

Addition of fulvestrant to erlotinib was well tolerated, with increased activity noted among EGFR wild type patients compared to erlotinib alone, albeit in an unplanned subset analysis.

Insulin resistance in an animal model of polycystic ovary disease is aggravated by vitamin D deficiency: Vascular consequences

Hyperandrogenic state in females is accompanied with metabolic syndrome, insulin resistance and vascular pathologies. A total of 67%-85% of hyperandrogenic women suffer also from vitamin D deficiency. We aimed to check a potential interplay between hyperandrogenism and vitamin D deficiency in producing insulin resistance and effects on coronary resistance arteries. Adolescent female rats were divided into four groups, 11-12 animals in each. Transdermal testosterone-treated and vehicle-treated animals were kept either on vitamin D-deficient or on vitamin D-supplemented diet for 8 weeks. Plasma sexual steroid, insulin, leptin and vitamin D plasma levels were measured, and oral glucose tolerance test was performed. In coronary arterioles, insulin receptor and vitamin D receptor expressions were tested by immunohistochemistry, and insulin-induced relaxation was measured in vitro on isolated coronary resistance artery segments. Testosterone impaired glucose tolerance, and it diminished insulin relaxation but did not affect the expression of insulin and vitamin D receptors in vascular tissue. Vitamin D deficiency elevated postprandial insulin levels and homeostatic model assessment insulin resistance. It also diminished insulin-induced coronary arteriole relaxation, while it raised the expression of vitamin D and insulin receptors in the endothelial and medial layers. Our conclusion is that both hyperandrogenism and vitamin D deficiency reduce sensitivity of coronary vascular tissue to insulin, but they do it with different mechanisms.

Clinically Observed Estrogen Receptor Alpha Mutations within the Ligand-Binding Domain Confer Distinguishable Phenotypes

OBJECTIVE

Twenty to fifty percent of estrogen receptor-positive (ER+) metastatic breast cancers express mutations within the ER ligand-binding domain. While most studies focused on the constitutive ER signaling activity commonly engendered by these mutations selected during estrogen deprivation therapy, our study was aimed at investigating distinctive phenotypes conferred by different mutations within this class.

METHODS

We examined the two most prevalent mutations, D538G and Y537S, employing corroborative genome-edited and lentiviral-transduced ER+ T47D cell models. We used a luciferase-based reporter and endogenous phospho-ER immunoblot analysis to characterize the estrogen response of ER mutants and determined their resistance to known ER antagonists.

RESULTS

Consistent with their selection during estrogen deprivation therapy, these mutants conferred constitutive ER activity. While Y537S mutants showed no estrogen dependence, D538G mutants demonstrated an enhanced estrogen-dependent response. Both mutations conferred resistance to ER antagonists that was overcome at higher doses acting specifically through their ER target.

CONCLUSIONS

These observations provide a tenable hypothesis for how D538G ESR1-expressing clones can contribute to shorter progression-free survival observed in the exemestane arm of the BOLERO-2 study. Thus, in those patients with dominant D538G-expressing clones, longitudinal analysis for this mutation in circulating free DNA may prove beneficial for informing more optimal therapeutic regimens.

Biochemistry of the menopause

The life of a human female is characterized from teenage years by monthly menstruation which ceases (the menopause) typically between the age of 40 and 60 years. The potential for reproduction declines and ceases as the ovaries become depleted of follicles. A transition period in mid-life, for 2 to 10 years, when menstruation is less regular is called the perimenopause. The menopause is associated with a significant decline in plasma concentrations of sex hormones, an increase in the concentrations of the gonadotrophins and changes in other hormones such as the inhibins. These changes are superimposed with effects of aging, social and metabolic factors, daily activity and well-being. Although the menopause is entirely natural, in some cases ovarian failure can occur earlier than usual; this is pathological and warrants careful biochemical investigations to distinguish it from conditions causing infertility. Elderly females are affected by a range of clinical disorders including endocrine, cardiovascular, skeletal, urogenital tract and immunological systems, body mass, vasomotor tone, mood and sleep pattern. Reference intervals for many diagnostic biochemical tests for the menopause need to be used when interpreting results in clinical investigations for patient management. The standardization and harmonization of assays are being addressed. Many women now choose to develop their career before bearing children, and the health service has had to change services around this. This review does not cover screening for and tests during pregnancy. The review is timely since the population is aging and there will be more demand on healthcare services.

Differences in testosterone and its precursors by sex of the offspring in meconium

Prenatal metabolism exerts profound effects on development. The first stool of the newborn, meconium, provides a window into the prenatal metabolic environment. The objective of this study was to examine the feasibility of meconium as a novel matrix to quantify prenatal steroid levels. We quantified parameters of analytical interest regarding the use of meconium, including sample stability. We hypothesized that meconium steroid content would differ by sex, prompting analysis of meconium to test effects of prenatal steroid metabolism. Meconium from 193 newborns enrolled in the Early Autism Risk Longitudinal Investigation (EARLI) study, including 107 males, and 86 females, were analyzed by isotope dilution-liquid chromatography-high resolution mass spectrometry (ID-LC-HRMS) while blinded to identity for testosterone (T), androstenedione (AD), and dehydroepiandrosterone (DHEA). Steroid levels were compared by sex, and investigations of potential trends resulting from sample storage or processing was conducted. The unconjugated steroid content of meconium in ng/g (mean, standard deviation) was for males: T (2.67, 8.99), AD (20.01, 28.12), DHEA (13.96, 23.57) and for females: T (0.82, 1.63), AD (22.32, 24.38), DHEA (21.06, 43.49). T was higher in meconium from males (p=0.0333), and DHEA was higher in meconium from females (p=0.0202). 6 female and 3 male T values were below the limit of detection. No extreme variability in hydration or trend in steroid levels by storage time was detected. Sexually dimorphic levels of hormones may reflect gestational differentiation, and future studies should consider meconium analysis.

Simultaneous quantification of estrogens, their precursors and conjugated metabolites in human breast cancer cells by LC-HRMS without derivatization

Liquid chromatography-mass spectrometry (LC-MS) is the state of the art technique for quantification of steroid hormones. Currently used methods are typically limited by the need of pre-column derivatization to increase ionization efficiency; however, this causes hydrolysis of conjugated metabolites. Our newly established LC-HRMS method is able to simultaneously quantify conjugated and unconjugated steroids without prior derivatization using deuterated internal standards and solid-phase extraction. This assay was validated according to ICH Q2(R1) guidelines for the analysis of the 10 main steroids of the estrogenic pathway, namely 4-androstene-3,17-dione, dehydroepiandrosterone (DHEA), DHEA-3-sulfate, estrone, 17β-estradiol, estriol (16α-OH-17β-estradiol), estrone-3-sulfate, 17β-estradiol-3-(β-d-glucuronide), 17β-estradiol-3-sulfate and testosterone. Assay performance characteristics were excellent with results for accuracy (98.8-101.2%), precision (mean: 2.05%, all ≤2.80%), stability over five freeze-thaw-cycles (95.7-100.4%) and SPE accuracy (96.9-102.0%), as well as suitable lower and upper limits of quantification for cell culture experiments (LLOQ 0.005-2ng/ml, ULOQ 3-2000ng/ml). Furthermore, we demonstrated the functionality of our method for the monitoring of steroid levels in the human breast cancer cell line MCF-7. This sensitive assay allows for the first time detailed investigations on estrogen metabolomics in breast cancer cells and may also apply to other estrogen-dependent tumor entities.

Validation of highly sensitive simultaneous targeted and untargeted analysis of keto-steroids by Girard P derivatization and stable isotope dilution-liquid chromatography-high resolution mass spectrometry

A multiplexed quantitative method for the analysis of three major unconjugated steroids in human serum by stable isotope dilution liquid chromatography-high resolution mass spectrometry (LC-HRMS) was developed and validated on a Q Exactive Plus hybrid quadrupole/Orbitrap mass spectrometer. This quantification utilized isotope dilution and Girard P derivatization on the keto-groups of testosterone (T), androstenedione (AD) and dehydroepiandrosterone (DHEA) to improve ionization efficiency using electrospray ionization. Major isomeric compounds to T and DHEA; the inactive epimer of testosterone (epiT), and the metabolite of AD, 5α-androstanedione (5α-AD) were completely resolved on a biphenyl column within an 18min method. Inter- and intra-day method validation using LC-HRMS with qualifying product ions was performed and acceptable analytical performance was achieved. The method was further validated by comparing steroid levels from 100μL of serum from young vs older subjects. Since this approach provides high-dimensional HRMS data, untargeted analysis by age group was performed. DHEA and T were detected among the top analytes most significantly different across the two groups after untargeted LC-HRMS analysis, as well as a number of other still unknown metabolites, indicating the potential for combined targeted/untargeted analysis in steroid analysis.

Endocrine Response Phenotypes Are Altered by Charcoal-Stripped Serum Variability

Charcoal-stripped bovine serum (CSS) is a critical reagent in the study of steroid hormones. However, CSS has high lot-to-lot variability, including residual growth factor and steroid hormone content. Assessing and reporting this variability is challenging but may affect experimental outcomes and data reproducibility. We hypothesized that CSS lot variability would affect endocrine response phenotypes in breast cancer cells, and we tested the effects of five individual CSS lots on endocrine response in MCF-7 and MDA MB 134VI (MM134) cells. Based on the effects of antiestrogens on MCF-7 cell proliferation, we defined CSS lots as having complete vs partial hormone deprivation. In partial deprivation CSS, the absolute effects of residual estrogens on cell proliferation were modest, but these effects masked the partial agonist activity of 4-hydroxytamoxifen in MM134 cells. Importantly, this effectively reversed the interpretation of tamoxifen-resistance in MM134 cells. Variable effects of CSS lots on endocrine resistance phenotypes were also observed in MCF-7 cells. In this context, we observed that partial vs complete deprivation CSS allowed for the development of unique early endocrine resistance phenotypes that correlated with the presence or absence of residual estrogenic hormones. We evaluated the methods of CSS preparation and identified factors contributing to the extent of hormone deprivation. Our observations suggest that CSS lot-to-lot variability has substantial effects on endocrine response phenotypes and that this ubiquitous factor in study methodology may confound reproducibility. Renewed vigilance in testing and reporting CSS phenotypes will greatly aid in interpreting and reproducing endocrine response and resistance data by the community.

Ultra-high sensitivity analysis of estrogens for special populations in serum and plasma by liquid chromatography-mass spectrometry: Assay considerations and suggested practices

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.

Role of mass spectrometry in steroid assays

In addition to protein hormones, steroids measurement constitutes the basis of modern endocrinology. Immunoassays have shown their limits in this field. In contrast, mass spectrometry shows an excellent sensitivity and specificity that make it the method of choice for steroids assays. The recent introduction of UHPLC-MS is a major advance which reinforces this position. In fact, mass spectrometry provides a lot of advantages such as determination of certain steroids in saliva, diagnosis of enzyme deficiencies, or measurement of molecules previously inaccessible like aldosterone. However, standardization is still needed to ensure good comparability of results between laboratories. In the future, mass spectrometry should not replace the immunoassays but rather complement it.

Derivatization of estrogens enhances specificity and sensitivity of analysis of human plasma and serum by liquid chromatography tandem mass spectrometry

Estrogens circulate at concentrations less than 20 pg/mL in men and postmenopausal women, presenting analytical challenges. Quantitation by immunoassay is unreliable at these low concentrations. Liquid chromatography tandem mass spectrometry (LC–MS/MS) offers greater specificity and sometimes greater sensitivity, but ionization of estrogens is inefficient. Introduction of charged moieties may enhance ionization, but many such derivatives of estrogens generate non-specific product ions originating from the “reagent” group. Therefore an approach generating derivatives with product ions specific to individual estrogens was sought.

Estrogens were extracted from human plasma and serum using solid phase extraction and derivatized using 2-fluoro-1-methylpyridinium-p-toluenesulfonate (FMP-TS). Electrospray in positive mode with multiple reaction monitoring using a QTrap 5500 mass spectrometer was used to quantify “FMP” derivatives of estrogens, following LC separation.

Transitions for the FMP derivatives of estrone (E1) and estradiol (E2) were compound specific (m/z 362→238 and m/z 364→128, respectively). The limits of detection and quantitation were 0.2 pg on-column and the method was linear from 1–400 pg/sample. Measures of intra- and inter-assay variability, precision and accuracy were acceptable (<20%). The derivatives were stable over 24 h at 10 °C (7–9% degradation). Using this approach, E1 and E2, respectively were detected in human plasma and serum: pre-menopausal female serum (0.5 mL) 135–473, 193–722 pmol/L; male plasma (1 mL) 25–111, 60–180 pmol/L and post-menopausal female plasma (2 mL), 22–78, 29–50 pmol/L.

Thus FMP derivatization, in conjunction with LC–MS/MS, is suitable for quantitative analysis of estrogens in low abundance in plasma and serum, offering advantages in specificity over immunoassay and existing MS techniques.

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Quantitative analysis of low amounts of estrone and estradiol in plasma and serum.

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Quantitation across physiological range in men and pre- and post-menopausal women.

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Methylpyridinium ether derivatives improve analytical specificity and sensitivity.

Ultrasensitive quantification of serum estrogens in postmenopausal women and older men by liquid chromatography-tandem mass spectrometry

An ultrasensitive stable isotope dilution liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed and validated for multiplexed quantitative analysis of six unconjugated and conjugated estrogens in human serum. The quantification utilized a new derivatization procedure, which formed analytes as pre-ionized N-methyl pyridinium-3-sulfonyl (NMPS) derivatives. This method required only 0.1mL of human serum, yet was capable of simultaneously quantifying six estrogens within 20min. The lower limit of quantitation (LLOQ) for estradiol (E2), 16α-hydroxy (OH)-E2, 4-methoxy (MeO)-E2 and 2-MeO-E2 was 1fg on column, and was 10fg on column for 4-OH-E2 and 2-OH-E2. All analytes demonstrated a linear response from 0.5 to 200pg/mL (5-2000pg/mL for 4-OH-E2 and 2-OH-E2). Using this validated method, the estrogen levels in human serum samples from 20 female patients and 20 male patients were analyzed and compared. The levels found for unconjugated serum E2 from postmenopausal women (mean 2.7pg/mL) were very similar to those obtained by highly sensitive gas chromatography-mass spectrometry (GC-MS) methodology. However, the level obtained in serum from older men (mean 9.5pg/mL) was lower than has been reported previously by both GC-MS and LC-MS procedures. The total (unconjugated+conjugated) 4-MeO-E2 levels were significantly higher in female samples compared with males (p<0.05). The enhanced sensitivity offered by the present method will allow for a more specific analysis of estrogens and their metabolites. Our observations might suggest that the level of total 4-MeO-E2 could be a potential biomarker for breast cancer cases.