Profiling oestrogens and testosterone in human urine by stable isotope dilution/benchtop gas chromatography-mass spectrometry

New liquid chromatography tandem mass spectrometry reference data for estradiol show mini-puberty in both sexes and typical pre-pubertal and pubertal patterns

CONTEXT

Reliable estradiol (E2) reference intervals (RIs) are crucial in pediatric endocrinology.

OBJECTIVES

This study aims to develop a sensitive ultra-performance liquid chromatographic tandem mass spectrometry (UPLC-MS/MS) method for E2 in serum, to establish graphically represented RI percentiles and annual RIs for both sexes, and to perform a systematic literature comparison.

METHODS

First, a UPLC-MS/MS method for E2 was developed. Second, graphically represented RI percentiles and annual RIs covering 0-18 years were computed (cohort of healthy children [1181 girls and 543 boys]). Subsequently, RIs were compared with published data by systematic searches.

RESULTS

Lower limit of quantification was 11 pmol/L, indicating high sensitivity. Estradiol first peaked during mini-puberty in both sexes (girls up to 192 pmol/L; boys up to 225 pmol/L). As could be expected, girls showed higher pubertal E2 (up to 638 pmol/L). However, boys' RIs (up to 259 pmol/L) overlapped considerably. We found 4 studies in the literature that also used LC-MS/MS to determine E2 and published RIs for the complete pediatric age range. Reference intervals varied considerably. Pre-pubertal and pubertal phases were present in all studies. Higher E2 during the time of mini-puberty in both sexes was documented in 3 studies including ours.

CONCLUSIONS

Variability of RIs for E2 between studies illustrates the importance of laboratory-specific RIs despite using a LC-MS/MS reference method. In boys, the striking E2 peak during mini-puberty as well as high pubertal E2 without phenotypic estrogenization in regular male puberty indicates that the role of E2 in children and, especially in boys, requires better functional understanding.

Optimization and validation of a GC-MS quantitative method for the determination of an extended estrogenic profile in human urine: Variability intervals in a population of healthy women

An analytical method based on GC-MS was developed for the determination of a wide panel of urinary estrogens, together with their principal metabolites. Because of the low concentration of estrogens in urine, an efficient sample pre-treatment was optimized by a design of experiment (DoE) procedure to achieve satisfactory sensitivity. A second DoE was built for the optimization of the chromatographic run, with the purpose of reaching the most efficient separation of analytes with potentially interfering ions and similar chromatographic properties. The method was fully validated using a rigorous calibration strategy: from several replicate analyses of blank urine samples spiked with the analytes, calibration models were built with particular attention to the study of heteroscedasticity and quadraticity. Other validation parameters, including the limit of detection, intra-assay precision and accuracy, repeatability, selectivity, specificity, and carry-over, were obtained using the same set of data. Further experiments were performed to evaluate matrix effect and extraction recovery. Then the urinary estrogen profiles of 138 post-menopausal healthy women were determined. These profiles provide a representation of physiological concentration ranges, which, in forthcoming studies, will be matched on the base of multivariate statistics with the urinary estrogenic profile of women with breast or ovarian cancer.

Advancements in the gold standard: Measuring steroid sex hormones by mass spectrometry

Sex hormones, such as testosterone and estrogens, play an essential role in regulating physiological and reproductive development throughout the lifetime of the individual. Although variation in levels of these hormones are observed throughout the distinct stages in life, significant deviations from reference ranges can result in detrimental effects to the individual. Alterations, by either an increase or decrease, in hormone levels are associated with physiological changes, decreased reproductive capabilities, and increased risk for diseases. Hormone therapies (HTs) and assisted reproductive technologies (ARTs) are commonly used to address these factors. In addition to these treatments, gender-affirming therapies, an iteration of HTs, are also a prominent treatment for transgender individuals. Considering that the effectiveness of these treatments relies on achieving therapeutic hormone levels, monitoring of hormones has served as a way of assessing therapeutic efficay. The need for reliable methods to achieve this task has led to great advancements in methods for evaluating hormone concentrations in biological matrices. Although immunoassays are the more widely used method, mass spectrometry (MS)-based methods have proven to be more sensitive, specific, and reliable. Advances in MS technology and its applications for therapeutic hormone monitoring have been significant, hence integration of these methods in the clinical setting is desired. Here, we provide a general overview of HT and ART, and the immunoassay and MS-based methods currently utilized for monitoring sex hormones. Additionally, we highlight recent advances in MS-based methods and discuss future applications and considerations for MS-based hormone assays.

Individual and cyclic estrogenic profile in women: Structure and variability of the data

The concentration of estrogens in the body fluids of women is highly variable, due to the menstrual cycle, circadian oscillations, and other physiological and pathological causes. To date, only the cyclic fluctuations of the principal estrogens (estradiol and estrone) have been studied, with limited outcome of general significance. Aim of the present study was to examine in detail the cyclic variability of a wide estrogens' panel and to interpret it by multivariate statistics. Four estrogens (17α-estradiol, 17β-estradiol, estrone, estriol) and eleven of their metabolites (4-methoxyestrone, 2-methoxyestrone, 16α-hydroxyestrone, 4-hydroxyestrone, 2-hydroxyestrone, 4-methoxyestradiol, 2-methoxyestradiol, 4-hydroxyestradiol, 2-hydroxyestradiol, estriol, 16-epiestriol, and 17-epiestriol) were determined in urine by a gas chromatography - mass spectrometry method, which was developed by design of experiments and fully validated according to ISO 17025 requirements. Then, urine samples collected every morning for a complete menstrual cycle from 9 female volunteers aged 24-35 years (1 parous) were analysed. The resulting three-dimensional data (subjects × days × estrogens) were interpreted using several statistical tools. Parallel Factor Analysis compared the estrogen profiles in order to explore the cyclic and inter-individual variability of each analyte. Principal Component Analysis (PCA) provided clear separation of the sampling days along the cycle, allowing discrimination among the luteal, ovulation, and follicular phases. The scores obtained from PCA were used to build a Linear Discriminant Analysis classification model which enhanced the recognition of the three cycle's phases, yielding an overall classification non-error rate equal to 90%. These statistical models may find prospective application in fertility studies and the investigation of endocrinology disorders and other hormone-dependent diseases.

Mass spectrometry-based metabolic signatures of sex steroids in breast cancer

Owing to controversy over the effects of steroids on breast cancer pathophysiology, comprehensive quantification of steroid hormones has been extensively considered in both clinical practice and biomarker discovery studies. In contrast to the traditional immunoaffinity-based assays, which show cross-reactivity and have poor validity at low levels of sex steroids, mass spectrometry is becoming a promising tool for measuring steroid levels in complex biological specimens. The Endocrine Society has announced and continuously updated on technical advances to apply high-quality breakthroughs in the clinical sciences. To avoid incorrect estimation of the steroids of interest, however, further emphasis should be made on the efficient separation by chromatography, such as gas and liquid chromatography, prior to mass spectrometric (MS) detection. Recent advances in MS-based analysis of sex steroids associated with breast cancer enable accurate quantification of circulating as well as localized steroids from frozen tissue slices, allowing these assays to be more powerful in clinical practice.

Change of the 5α/5β ratio of urinary steroid metabolites in benign prostatic hyperplasia patients treated with dutasteride

BACKGROUND

The effects of the administration of dutasteride (DUT) on steroid metabolite pathways in BPH patients have not been examined.

METHODS

Urine and blood samples as well as clinical parameters were prospectively collected after the administration of DUT to 60 BPH patients, and after its withdrawal in another set of 25 BPH patients. Urine samples were assessed using gas chromatography/mass spectrometry for the urinary steroid profile (USP), which simultaneously measures 63 steroid metabolites. We examined pharmacological changes in the 5α/5β ratio of urinary metabolites and their relationships with clinical parameters in patients treated with DUT.

RESULTS

The mean urinary androsterone/etiocholanolone (An/Et) ratio in sex-steroid pathways significantly decreased from 1.39 to 0.02 (p < 0.01). Urinary metabolites in other steroid pathways such as 5αTHF/5βTHF in the glucocorticoid pathway and 5αTHB/5βTHB in the mineralocorticoid pathway also significant decreased after the DUT treatment. As compared to baseline level, the mean An/Et ratios in patients with the withdrawal of DUT were 0.7%, 1.4%, 12.6%, and 82.4% at just before, one month, 3 months, and 6 months after the withdrawal of DUT, respectively. All other steroid pathways changed in a similar manner without the aggravation of urinary symptoms. The recovery ratio of An/Et in USP before and 3 months after the withdrawal of DUT correlated with the recovery ratio of serum PSA levels (ρ = 0.61, p < 0.01).

CONCLUSION

Urinary 5α/5β metabolites in all pathways were strongly suppressed after the administration of DUT for one month and the pharmacological effect of DUT prolonged even after withdrawal of DUT.

Quantifying endogenous androgens, estrogens, pregnenolone and progesterone metabolites in human urine by gas chromatography tandem mass spectrometry

A method for the quantitation of 22 urinary steroids (androgens, estrogens and the main pregnenolone and progesterone metabolites) by means of gas chromatography tandem mass spectrometry using a triple quadrupole analyzer has been developed. Two different enzymatic hydrolysis protocols were investigated; one capable of releasing steroids present as both sulfates and glucuronides (total fraction), and another with β-glucuronidase activity only. After selecting adequate internal standards and choosing the optimal instrumental parameters, i.e. chromatographic separation and ion transition conditions, the method was fully validated using both hydrolysis protocols. The method was shown to be linear (r >0.99) in the range of endogenous concentrations for all studied steroids with extraction recoveries higher than 80%. The use of labeled internal standards allowed for both a correct quantification and the evaluation of the rate of deconjugation for sulfates and glucuronides in every sample. In general, the sensitivity of the method was suitable for the detection of the endogenous levels, with limits of quantification ranging from 0.1 to 20ng/mL. Accuracies ranging from 80% to 120%, and relative standard deviations below 25% in intra- and inter- assay experiments were found for most of the analytes. The applicability of the validated method was tested by quantifying twenty-two metabolites in 24-h urine samples collected from healthy individuals. The ranges for the excretion of steroids in the total and glucuronide fractions obtained with the new method were compared with those available in the literature. By comparing the figures in both fractions, an estimation of the percentage that the sulfation represents for each steroid was also calculated. The presence of side enzymatic activities and the utility of the method for clinical studies as well as for doping control analysis is discussed.

Voltammetric Behavior of Testosterone on Bismuth Film Electrode: Highly Sensitive Determination in Pharmaceuticals and Human Urine by Square‐Wave Adsorptive Stripping Voltammetry

In this paper, an electrochemical application of bismuth‐film electrode (BiFE) fabricated via ex‐situ electrodeposition onto a glassy carbon electrode for testosterone determination was investigated in aqueous and aqueous/surfactant solutions. In cyclic voltammetry, the compound showed one irreversible and adsorption‐controlled reduction peak. The BiFE revealed good linear response in the examined concentration range of 1 to 45 nmol L−1 testosterone in BrittonRobinson buffer, pH 5.0 containing 3 mmol L−1 cetyltrimethylammonium bromide. The limit of detection was 0.3 nmol L−1 (0.09 ng mL−1). Finally, the BiFE was satisfactorily applied for quantitation of testosterone in both pharmaceutical (oil‐based ampoule) and biological (human urine) samples.

Urinary proteomics and metabolomics in the diagnosis of pediatric disorders

Proteomics is the study of structures and functions of proteins, while metabolomics is the study of small-molecule metabolites in the cells, tissues, and organs of the organism. Proteomic technologies have wide applications in medical field. The current revolution in proteomics has led to the discovery of several new protein markers for various disorders. Urinary proteomics and metabolomics have also evolved in the recent years, for the diagnosis of both renal and nonrenal disorders. The urinary proteome varies in normal and abnormal conditions. Different techniques are employed for the analysis of pediatric urinary proteome, the commonest being MS. Before introduction into clinical use, there is the need for careful standardization. Available data suggest that there are differences in urinary proteome between adult and pediatric populations. It is noted that infant urine contains proteins involved in translation and transcription, cellular growth, and metabolic processes, which are not predominant in adult urine. Available data on urinary proteomic and metabolomic profile in common pediatric disorders are also reviewed here.

Simultaneous determination of endocrine disrupting compounds bisphenol F and bisphenol AF using carboxyl functionalized multi-walled carbon nanotubes modified electrode

A novel, simple and selective electrochemical method was developed for simultaneous determination of bisphenol F (BPF) and bisphenol AF (BPAF) in aqueous media (phosphate buffer solution, pH 6.0) on carboxyl functionalized multi-walled carbon nanotubes modified glassy carbon electrode (MWCNT-COOH/GCE) using differential pulse voltammetry (DPV). In DPV, MWCNT-COOH/GCE could separate the oxidation peak potentials of BPF and BPAF present in the same solution though, at the bare GCE, the peak potentials were indistinguishable. The results showed that the electrochemical sensor exhibited excellent electrocatalytic activity towards the oxidation of the two analytes. The peak current in DPV of BPF and BPAF increased linearly with their concentration in the ranges of 0.6-1.6 mmol/L BPF and 0.6-1.6 mmol/L BPAF. The detection limits were 0.1243 mmol/L and 0.1742 mmol/L (S/N=3) correspondingly. The modified electrode was successfully used to simultaneously determine BPF and BPAF in real samples.

Profiling intact steroid sulfates and unconjugated steroids in biological fluids by liquid chromatography-tandem mass spectrometry (LC-MS-MS)

Within the combined DFG research project "Sulfated Steroids in Reproduction" an analytical method was needed for determining sulfated and unconjugated steroids with highest specificity out of different biological matrices such as aqueous solution, cell lysate and serum. With regard to this analytical challenge, LC-MS-MS presents the technique of choice because it permits (1) analysis of the intact steroid conjugate, (2) allows for simultaneous determination of multiple analytes (profiling, targeted metabolomics approach) and (3) is independent of phenomena such as cross-reactivity. Sample work up consisted of incubation of sample with internal standards (deuterium labeled steroids) followed by solid phase extraction. Only serum samples required a protein precipitation step prior to solid phase extraction. The extract was divided in two parts: six steroid sulfates (E1S, E2S, AS, 16-OH-DHEAS, PREGS, DHEAS) were analyzed by C18aQ-ESI-MS-MS in negative ion mode and eleven unconjugated steroids (E3, 16-OH-DHEA, E1, E2, (4)A, DHEA, T, 17-OH-PREG, Prog, An, PREG) were analyzed by C18-APCI-MS-MS in positive ion mode. For steroid sulfates, we found high sensitivities with LoQ values ranging from 0.08 to 1 ng mL(-1). Unconjugated steroids showed LoQ values between 0.5 and 10 ng mL(-1). Calibration plots showed excellent linearity. Mean intra- and inter-assay CVs were 2.4% for steroid sulfates and 6.4% for unconjugated steroids. Accuracy - determined in a two-level spike experiment - showed mean relative errors of 5.9% for steroid sulfates and 6.1% for unconjugated steroids. In summary, we describe a novel LC-MS-MS procedure capable of profiling six steroid sulfates and eleven unconjugated steroids from various biological matrices.

Ultra performance liquid chromatography-tandem mass spectrometry method for profiling of steroid metabolome in human tissue

In humans, steroids play a broad and vital role in regulation of gene expression, secondary sexual characteristics, maturation, reproduction, cardiovascular health, neurological functions, etc., but imbalance in steroid metabolism is also linked to development and progression of many diseases, such as cancer, neurodegenerative diseases, and cardiovascular diseases. Hence, measurement of steroids in biological samples is essential to monitor human health. Currently, there is radioimmunoassay, gas chromatography-mass spectrometry (GC/MS), and liquid chromatography-mass spectrometry (LC-MS) methods developed for steroid measurements in biological samples. However, these methods require elaborate sample preparation procedures and have concerns(s) related to reproducibility, dynamic range, time, costs, and most importantly the total coverage of steroids. Also currently, there is no method available for comprehensive steroid profiling in a single LC-MS run that includes androgens, corticosteroids, progestogens, estrogens, estrogen metabolites, estrogen conjugates, and estrogen-DNA adducts as well as exogenous steroid derivatives. Here, I present a global steroid metabolic profiling method based on liquid-liquid extraction (LLE) followed by ultra performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS) for simultaneous measurement of over 100 indigenous as well as exogenous steroids in about 12 min, without derivatization. The method was successfully applied to determine steroid hormone levels in the breast tissue of healthy women. Overall presence of all major classes of steroids as well as estrogen derivatives was detected in breast tissue.

Estrogen receptor GPR30 reduces oxidative stress and proteinuria in the salt-sensitive female mRen2.Lewis rat

The current study assessed whether activation of the novel estrogen receptor GPR30 ameliorates salt-dependent renal damage in intact mRen2.Lewis (mRen2) females. Hemizygous mRen2 rats were maintained on either a normal salt (0.5% Na) or high-salt (HS; 4.0% Na) diet for 10 weeks (5 to 15 weeks of age), and HS animals were treated with the GPR30 agonist G-1 or vehicle for 2 weeks. Systolic blood pressure markedly increased with HS diet (149±3 to 219±5 mm Hg; P<0.01), but G-1 did not influence pressure (P=0.42). G-1 and estradiol induced relaxation of preconstricted mesenteric vessels from normal salt mRen2 rats, but both responses were attenuated in the HS group. Despite the lack of an effect on blood pressure, G-1 decreased renal hypertrophy, proteinuria, urinary 8-isoprostane excretion, and tubular 4-hydroxynonenal staining. HS diet significantly increased GPR30 mRNA (1.01±0.04 versus 1.59±0.13; P<0.01) and protein (0.60±0.31 versus 3.99±0.75; P<0.01) in the renal cortex. GPR30 was highly expressed in the brush border of proximal tubules and colocalized with megalin. Finally, megalin expression was reduced by HS diet and restored with G-1. We conclude that GPR30-mediated beneficial effects in salt-sensitive mRen2 females occurred independent of changes in systolic blood pressure. The failure of G-1 to influence pressure may reflect a salt-induced impairment in GPR30-mediated vasorelaxation. The renoprotective actions of GPR30 may involve attenuation of tubular oxidative stress and activation of megalin-mediated protein reabsorption.

Prepubertal urinary estrogen excretion and its relationship with pubertal timing

Whether prepubertal estrogen production impacts on the timing of puberty is not clear. We aimed to investigate prepubertal 24-h estrogen excretion levels and their association with early and late pubertal markers. Daily urinary excretion rates of estrogens of 132 healthy children, who provided 24-h urine samples 1 and 2 yr before the start of the pubertal growth spurt [age at takeoff (ATO)], were quantified by stable isotope dilution/GC-MS. E-sum3 (estrone + estradiol + estriol) was used as a marker for potentially bioactive estrogen metabolites and E-sum5 (E-sum3 + 16-epiestriol + 16-ketoestradiol) for total estrogen production. Pubertal outcomes were ATO, age at peak height velocity (APHV), duration of pubertal growth acceleration (APHV-ATO), age at Tanner stage 2 for pubic hair (PH2), genital (G2, boys) and breast (B2, girls) development, and age at menarche. Prepubertal urinary estrogen excretions (E-sum3 and E-sum5) were not associated with ATO, APHV, and age at PH2 but with duration of pubertal growth acceleration (P < 0.01) in both sexes. Girls with higher E-sum3 reached B2 0.9 yr (P = 0.04) and menarche 0.3 yr earlier (P = 0.04) than girls with lower E-sum3. E-sum3 was not associated with age at G2 in boys (P = 0.6). For most pubertal variables, the associations with E-sum3 were stronger than with E-sum5. In conclusion, prepubertal estrogens may not be critical for the onset of the pubertal growth spurt but are correlated with its duration in both boys and girls. Prepubertal estrogen levels may already predict the timing of girls' menstruation and breast development but do not appear to affect sexual maturation in boys.