The plasma free fraction of 25-hydroxyvitamin D3 is not strongly associated with 25-hydroxyvitamin D3 clearance in kidney disease patients and controls.

Circulating 25-hydroxyvitamin D [25(OH)D] concentration is used to monitor vitamin D status. Plasma protein binding may influence the 25(OH)D dose-response to vitamin D treatment through a direct relationship between the plasma unbound ("free") fraction and clearance of 25(OH)D. We previously evaluated 25(OH)D3 clearance in relation to kidney function using intravenous administration of deuterium labeled 25(OH)D3. In this follow up study, we determined the free fraction of 25(OH)D3 in plasma (i.e., percent free 25(OH)D3) and the serum concentration and haplotype of vitamin D binding protein in these participants. We hypothesized that the percent free 25(OH)D3 would be positively associated with 25(OH)D3 clearance and would mediate associations between clearance and vitamin D binding protein (GC) haplotypes. Participants were mean (SD) age 64 (10) years and included 42 individuals with normal kidney function (controls), 24 individuals with chronic kidney disease, and 19 individuals with kidney failure on hemodialysis. Free plasma 25(OH)D2 and 25(OH)D3 concentrations were quantified with a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Because there is no reference measurement procedure for free 25(OH)D, we compared the new method with a widely-used predictive equation and a commercial immunoassay. The percent free 25(OH)D3 determined by predictive equation was weakly associated with 25(OH)D3 clearance (R = 0.27; P = 0.01). However, this association was absent when percent free 25(OH)D3 was determined using LC-MS/MS-measured free and total 25(OH)D3 concentrations. Method comparison uncovered a negative bias in immunoassay-measured free 25(OH)D concentrations among participants with kidney failure, so immunoassay results were not used to evaluate the association between percent free 25(OH)D3 and clearance. GC2 haplotype carriage was associated with 25(OH)D3 clearance. Among individuals with 2 relative to no GC2 alleles, clearance was 87 (95% CI: 15-158) mL/d greater. However, in contrast with the literature, GC2 carriage was not significantly related to DBP concentration or the percent free 25(OH)D3 (either predicted or measured). In conclusion, the free fraction of 25(OH)D3 is not strongly associated with 25(OH)D3 clearance but may explain small differences in clearance according to GC haplotype.

Glycosylation Profiling of the Neoplastic Biomarker Alpha Fetoprotein through Intact Mass Protein Analysis.

Elevated serum alpha-fetoprotein (AFP) can be observed in liver cirrhosis and hepatocellular carcinoma (HCC). The glycosylation patterns of AFP have been shown to differentiate these conditions, with AFP glycoforms with core fucosylation (AFP-L3) serving as a malignancy risk predictor for HCC. We have developed a method to detect endogenously present AFP proteoforms and to quantify the relative abundance of AFP-L3 glycoforms (AFP-L3%) in serum samples. This method consists of immune enrichment of endogenous AFP, followed by liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) intact protein analysis of AFP. Data are available via ProteomeXchange with identifier PXD038606. Based on the AFP profiles in authentic patient serum samples, we have identified that the frequently observed AFP glycoforms without core fucosylation (AFP-L1) are G2S2 and G2S1, and common AFP-L3 glycoforms are G2FS1 and G2FS2. The intensities of glycoforms in the deconvoluted spectrum are used to quantify AFP-L3% in each sample. The method evaluation included reproducibility, specificity, dilution integrity, and comparison of AFP-L3% with a lectin-binding gel shift electrophoresis (GSE) assay. The AFP-L1 and AFP-L3 proteoforms were reproducibly identified in multiple patient serum samples, resulting in reproducible AFP-L3% quantification. There was considerable agreement between the developed LC-HRMS and commercial GSE methods when quantifying AFP-L3% (Pearson r = 0.63) with a proportional bias.

LC-MS/MS Method for High-Throughput Analysis of Methylmalonic Acid in Serum, Plasma, and Urine: Method for Analyzing Isomers Without Chromatographic Separation.

Measurement of methylmalonic acid (MMA) plays an important role in the diagnosis of vitamin B12 deficiency. Vitamin B12 is an essential cofactor for the enzymatic carbon rearrangement of methylmalonyl-CoA (MMA-CoA) to succinyl-CoA (SA-CoA), and the lack of vitamin B12 leads to elevated concentrations of MMA. Measurement of MMA in biological samples is complicated because of the presence of succinic acid (SA), isomer of MMA. We developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for MMA. The method utilizes derivatization and positive ion mode ionization, which is specific to polycarboxylic acids (MMA and SA are dicarboxylic acids), while derivatives of monocarboxylic acids at these conditions are not ionizable and not detectable. The only organic acid, other than MMA, that is detected in this method is SA. The described method does not require chromatographic resolution of the peaks of MMA and SA; quantitative measurement of MMA is performed using a deconvolution algorithm, which mathematically resolves signal corresponding to MMA, from the combined signal of MMA/SA. Because of the high selectivity of detection, this method utilizes isocratic chromatographic separation; reconditioning and re-equilibration of the chromatographic column between injections is unnecessary. The above features allow high-throughput analysis of MMA with injection-to-injection cycle time of approximately 1 minute.

High Sensitivity Measurement of Parathyroid Hormone-Related Protein (PTHrP) in Plasma by LC-MS/MS.

N-terminal sequence of parathyroid hormone-related protein (PTHrP) has close homology to parathyroid hormone (PTH). In health, both PTH and PTHrP participate in calcium regulation and homeostasis, but some of the functions, such as regulation of bone development, teeth eruption, calcium regulation in central nervous system, and calcium regulation during pregnancy and fetal development, are unique to PTHrP. In pathology, PTHrP is involved in activation of the pathways, allowing tumor cells to form bone metastasis. In contemporary clinical practice, measurements of PTHrP are used for diagnosing and management of patients suspected of hypercalcemia of malignancy. We describe high-sensitivity, high-specificity LC-MS/MS method for measurement of PTHrP. Sample preparation in this method is performed as follows: internal standard (15N labeled PTHrP) is added to plasma samples. PTHrP and the internal standard are enriched from the samples using anti-PTHrP antibody conjugated to magnetic beads. The beads are washed, PTHrP is digested with trypsin, and a PTHrP-specific signature peptide is analyzed using LC-MS/MS. The lower limit of detection, limit of quantitation, and upper limit of linearity of the assay are 0.5, 2, and 600 pmol/L; total imprecision of the method is <10%. Reference intervals for PTHrP established using this method in samples of healthy women and men are <3.4 pmol/L and < 2.3 pmol/L, respectively. The method has acceptable performance for use in clinical diagnostic applications.

LC-MS/MS Method for Measurement of Thiopurine Nucleotides (TN) in Erythrocytes and Association of TN Concentrations With TPMT Enzyme Activity.

Monitoring concentrations of thiopurine metabolites is used clinically to prevent adverse effects in patients on thiopurine drug therapy. We developed a LC-MS/MS method for the quantification of 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP) in red blood cells (RBCs). This method utilizes an automated cell washer for RBC separation from whole blood samples and washing of the separated RBCs. The lower limit of quantification of the method was 0.2 µmol/L for 6-TG (∼50 pmol/8 × 108 RBC) and 4 µmol/L for 6-MMP (∼1,000 pmol/8 × 108 RBC). The total imprecision of the assay was <3.0%. The upper limit of linearity for 6-TG and 6-MMP was 7.5 µmol/L and 150 µmol/L, respectively. The stability of the thiopurine metabolites under pre- and post-analytically relevant conditions was also evaluated. A good agreement was observed between this method and validated LC-MS/MS methods from three laboratories, except for ∼40% low bias for 6-MMP observed in one of the methods. The assessment of the association between 6-TG and 6-MMP concentrations with thiopurine S-methyltransferase (TPMT) phenotype and genotype demonstrated a statistically significant difference in the thiopurine metabolite concentrations between the TPMT groups with normal and intermediate activity of 6-MMP (p < 0.0001), while the difference in 6-TG concentrations was statistically not significant (p = 0.096). Among the samples with normal TPMT activity, higher concentrations of 6-MMP (p = 0.015) were observed in pediatric samples than in the samples of adults. No statistically significant differences were observed in the distributions of 6-TG and 6-MMP concentrations among the evaluated genotypes.

Endogenous sex hormones, aromatase activity and lung cancer risk in postmenopausal never-smoking women.

Although reproductive factors have been repeatedly associated with lung cancer risk, no study to date has directly evaluated the relationship with endogenous sex hormones nor with aromatase activity in postmenopausal never-smoking women. A case-control study of 397 incident lung cancer cases and their individually matched controls, nested within the Shanghai Women's Health Study, was conducted among postmenopausal women who were lifetime never smokers. Prediagnostic concentrations of sex hormones was quantitated using LC-MS/MS assays in plasma. The product-substrate molar ratio of estrone to androstenedione was used as an index of aromatase activity (IAA). Multivariable conditional logistic regression models were used to calculate odds ratios (ORs) for lung cancer. Baseline concentrations of estradiol, free testosterone and IAA were inversely associated with subsequent risk of lung cancer in multivariable-adjusted models. When further adjusted for body mass index, the inverse association with estradiol was attenuated and no longer statistically significant, but the association with free testosterone and IAA remained. In analyses confined to participants having never used menopausal hormone therapy in 376 case-control pairs, the inverse association with free testosterone and IAA was slightly strengthened. OR for the highest vs the lowest quartile of free testosterone was 0.55 (95% CI = 0.34-0.90; Ptrend  = .03), and the corresponding OR for IAA was 0.57 (95% CI = 0.34-0.96; Ptrend  = .04). Our study, for the first time, suggests that higher levels of circulating free testosterone and estimated aromatase activity may be associated with lower lung cancer risk in postmenopausal never-smoking women.

Clinical Utility and Analytical Aspects of Direct Measurements of Free Hormones Using Mass Spectrometry-Based Methods.

BACKGROUND: The free hormone (FH) hypothesis states that hormone action and the corresponding biological effects are mediated by the unbound (free) fraction of hormone in circulation. The in vivo relationship between protein-bound and FH is complex and dynamic. In most individuals, measurement of total hormone (TH) is usually adequate to reflect the hormone status; however, certain physiological conditions and/or medications can affect protein binding and alter FH concentration. In these cases, measurement of FH will provide a better measure of the bioactive hormone status than measurement of the TH. Measurement of FH presents many challenges, as the concentrations are very low and there are number of pitfalls, which may affect the measured concentrations. CONTENT: In this review, we discuss techniques used in the separation and direct quantitation of FH concentrations in biological samples using mass spectrometry for analysis. We also highlight clinical situations in which FH analysis is warranted and when mass spectrometry should be the preferred methodology over immunoassays. SUMMARY: Equilibrium dialysis, ultrafiltration, or size-exclusion separation coupled with liquid chromatography-tandem mass spectrometry provides a sensitive and specific method to measure FH concentrations. These direct methods are useful in iatrogenic or physiological states that alter hormone binding or metabolism.

A high sensitivity LC-MS/MS method for measurement of 3-methoxytyramine in plasma and associations between 3-methoxytyramine, metanephrines, and dopamine.

INTRODUCTION: Diagnosis of pheochromocytoma and paraganglioma (PPGL) is aided by the measurement of metanephrine (MN) and normetanephrine (NMN). Research suggests that 3-methoxytyramine (3MT), a dopamine (DA) metabolite, may serve as a biomarker of metastasis in patients with paraganglioma. Considering the very low endogenous plasma 3MT concentrations (<0.1 nM), highly sensitive and specific methods for 3MT are needed. METHODS: We developed a simple method for measurement of 3MT. Sample preparation was performed using solid phase micro-extraction with the eluates injected directly onto the LC-MS/MS. Data acquisition was performed in multiple reaction monitoring mode with an instrumental analysis time of 3 min per sample. We evaluated the method's performance and analyzed samples from healthy individuals and pathological specimens. RESULTS: The limit of quantitation and upper limit of linearity were 0.03 nM and 20 nM, respectively. The intra-/inter-day imprecision for pooled plasma samples at concentrations of 0.04 nM, 0.2 nM, and 2 nM was 10.7%/18.3%, 4.5%/8.9%, and 3.1%/0.9%, respectively. Among samples with MN, NMN, or both MN and NMN above the reference intervals (RIs), 0%, 16% and 46%, respectively, showed 3MT greater than the proposed upper RI value of 0.1 nM; 12% of samples with DA above the RI had 3MT above 0.1 nM. CONCLUSIONS: The developed method allowed accurate quantitation of 3MT in patient samples and would provide valuable information to clinicians diagnosing or monitoring patients with PPGL. High 3MT concentrations in patient samples with MN and NMN within the respective RIs may alert clinicians of the possibility of a DA-producing tumor.

Concentrations of nine endogenous steroid hormones in 70-year-old men and women.

OBJECTIVES: Circulating concentrations of endogenous steroids have systemic implications on health in elderly. However, population-based age- and ethnicity-specific data are scarce. The aim was to report sex-specific plasma concentrations of endogenous sex and adrenal steroids in elderly Swedish Caucasians, to examine the impact of BMI and to present concentrations in apparently healthy subjects. METHODS: A population-based observational study of 70-year olds, including 684 community-dwelling men and women enrolled in the PIVUS study, Sweden. Median plasma concentrations were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for pregnenolone, 17-hydroxypregnenolone, 17-hydroxy-progesterone, 11-deoxycortisol, DHEA, androstenedione, testosterone, estrone and estradiol. RESULTS: Plasma concentrations were significantly higher in men (n = 452) than in women (n = 232) for estradiol: median 61.3 pmol/L (95% CI, 11.4, 142.7) vs 18.4 (4.0, 127.3), for estrone: 92.8 (33.3, 206) vs 71.6 (17.8, 209) pmol/L, and for testosterone 13.8 (5.7, 28.0) vs 0.7 (0.2, 2.0) nmol/L. Higher concentrations of estrone and estradiol were observed in obese than non-obese women. Compared to non-obese men, obese men had lower concentrations of testosterone and its precursors: 17-hydroxypregnenolone, 17-hydroxyprogesterone, androstenedione and DHEA. The subgroup of apparently healthy individuals had median values > 20% lower for estrone and estradiol in women but slightly higher for testosterone in both sexes. CONCLUSIONS: Concentrations of estradiol, estrone and testosterone were higher in 70-year-old men than in women. BMI associated positively to estradiol and estrone in women and negatively to testosterone in men. Apparently healthy women had lower median concentrations of estradiol and estrone and men had higher median testosterone compared to all individuals.

Development and Clinical Evaluation of a High-Throughput LC-MS/MS Assay for Vitamin B6 in Human Plasma and Serum.

BACKGROUND: Pyridoxal 5'-phosphate (PLP) is the primary circulatory form of vitamin B6, an essential cofactor for numerous biochemical enzymatic reactions. Conventional PLP analysis using high-performance liquid chromatography (HPLC) with fluorescence requires derivatization and long injection-to-injection time. Development of high-throughput LC-MS/MS assays is desirable. METHODS: Stable isotope labeled internal standard was added to aliquots of samples, proteins were precipitated using trichloroacetic acid, and supernatants were analyzed by multiple reaction monitoring using LC-MS/MS in positive ion mode. Analysis time for PLP was 3.0 min using single column HPLC separation and 2.4 min using alternating column regeneration (ACR). Clinical evaluation of the method included review of results (n = 102 386) from routine performance of the assay. RESULTS: The assay was linear to 500 nmol/L; limit of quantification was 5 nmol/L. Imprecision (CV) of the assay was <5%. Equivalent performance was observed for single HPLC column and ACR. In 62% of routinely analyzed patient samples, PLP concentrations were within the reference interval; higher PLP concentrations were observed in samples from males than from females. Vitamin B6 deficiency was lowest in children and highest in elderly adults. Lower PLP concentrations were observed in samples collected during winter/spring than during summer/fall. We observed lower concentrations in plasma collected in lithium heparin tubes, suggesting PLP degradation caused by the anticoagulant. CONCLUSIONS: This LC-MS/MS method allows PLP determination using simple sample preparation and short analysis time. We observed association of PLP concentrations with age, sex, and season of sample collection. Our data indicate that lithium heparin anticoagulant tubes reduce measured PLP concentration.

Developmental low-dose exposure to bisphenol A induces chronic inflammation, bone marrow fibrosis and reduces bone stiffness in female rat offspring only.

BACKGROUND: Developmental exposure to low doses of the endocrine disruptor bisphenol A (BPA) is known to alter bone tissue in young rodents, although how bone tissue is affected in aged animals is not well known. We have recently shown that low-dose developmental exposure to BPA increases procollagen type I N-terminal propeptide (P1NP) levels, a peptide formed during type 1 collagen synthesis, in plasma of 5-week-old female rat offspring while male offspring showed reduced bone size. OBJECTIVE: To analyze offspring bone phenotype at 52 weeks of age and clarify whether the BPA-induced increase in P1NP levels at 5 weeks is an early sign of bone marrow fibrosis development. METHODS: As in our 5-week study, pregnant Fischer 344 rats were exposed to BPA via drinking water corresponding to 0.5 µg/kg BW/day (BPA0.5), which is in the range of human daily exposure, or 50 µg/kg BW/day (BPA50) from gestational day 3.5 until postnatal day 22. Controls were given only vehicle. The offspring were sacrificed at 52 weeks of age. Bone effects were analyzed using peripheral quantitative and micro-computed tomography (microCT), 3-point bending test, plasma markers and histological examination. RESULTS: Compared to a smaller bone size at 5 weeks, at the age of 52 weeks, femur size in male offspring had been normalized in developmentally BPA-exposed rats. The 52-week-old female offspring showed, like the 5-week-old siblings, higher plasma P1NP levels compared to controls but no general increasing bone growth or strength. However, 2 out of 14 BPA-exposed female offspring bones developed extremely thick cortices later in life, discovered by systematic in vivo microCT scanning during the study. This was not observed in male offspring or in female controls. Biomechanical testing revealed that both doses of developmental BPA exposure reduced femur stiffness only in female offspring. In addition, histological analysis showed an increased number of fibrotic lesions only in the bone marrow of female rat offspring developmentally exposed to BPA. In line with this, plasma markers of inflammation, Tnf (in BPA0.5) and Timp1 (in BPA50) were increased exclusively in female offspring. CONCLUSIONS: Developmental BPA exposure at an environmentally relevant concentration resulted in female-specific effects on bone as well as on plasma biomarkers of collagen synthesis and inflammation. Even a dose approximately eight times lower than the current temporary EFSA human tolerable daily intake of 4 µg/kg BW/day, appeared to induce bone stiffness reduction, bone marrow fibrosis and chronic inflammation in female rat offspring later in life.

Association of PTHrP levels in CSF with Alzheimer's disease biomarkers.

BACKGROUND: Parathyroid hormone-related protein (PTHrP) is involved in intracellular calcium regulation, neural cell proliferation and synaptic transmission. To date, no studies have been performed to evaluate the potential of PTHrP concentrations in cerebrospinal fluid (CSF) as a biomarker of brain pathophysiology. In this study we evaluated the association between CSF concentrations of PTHrP with the core CSF biomarkers of Alzheimer's disease (AD). METHODS: PTHrP and calcium were analysed using validated mass spectrometry based methods in a set of CSF samples that tested positive (n = 45) and negative (n = 45) for the AD biomarkers, including total tau protein (T-tau), phosphorylated tau protein (P-tau) and amyloid-ß 42 (Aß42). The measured CSF concentrations of PTHrP and calcium (Ca) were evaluated for association with AD CSF biomarkers. RESULTS: PTHrP and Ca concentrations in CSF samples ranged between 25 and 137 pmol/L and 0.92-1.53 mmol/L, respectively. Higher concentrations of PTHrP were observed in association with increased concentrations of T-tau and P-tau in the AD and the control group; while a stronger correlation was observed in the control group (ρ = 0.6, p < 0.0001; and ρ = 0.72, p < 0.0001, for T-tau and P-tau, respectively). Negative correlation was observed between concentrations of PTHrP and Aß42 in the AD group (ρ = 0.27, p = 0.015). A statistically significantly lower ratio Aß42/PTHrP was observed in the AD group (p < 0.0001). CONCLUSION: In the current study, we observed an association of PTHrP concentrations with concentrations of clinically used CSF biomarkers of AD. Concentrations of PTHrP were positively correlated with concentrations of T-tau and P-tau, suggesting an association with neuronal secretion and function, which is reduced upon progression to AD pathology. Our data suggest potential utility of the Aß42/PTHrP ratio in assessment of AD progression.

Low-dose exposure to Bisphenol A during development has limited effects on male reproduction in midpubertal and aging Fischer 344 rats.

Low doses of Bisphenol A (BPA) during development may affect reproduction. In this study, Fischer 344 rats were exposed to 0.5 or 50 µg BPA/kg bw/day via drinking water from gestational day 3.5 to postnatal day 22. Anogenital distance, organ weight, histopathology of reproductive organs, hormone analysis and sperm morphology were evaluated in male offspring. In this study no major effects of BPA on male reproduction in midpubertal (postnatal day 35) or adult (12-month-old) rats were revealed, apart from a higher prevalence of mild inflammatory cell infiltrate in cauda epididymis in adult rats exposed to 50 µg BPA/kg bw/day. No BPA-related effects on sexual development were seen but care should be taken when evaluating histopathology in midpuberty testis due to large morphological variation. Results from the present study show no major signs of altered male reproduction in rats exposed to low doses of BPA during gestation and lactation.

Parathyroid hormone related protein concentration in human serum and CSF correlates with age.

BACKGROUND: Parathyroid Hormone-Related Protein (PTHrP) is involved in intracellular calcium (Ca) regulation, and has been demonstrated to participate in regulation of Ca in brain cells, activation of neurons, and modulation of pain. However, there are conflicting reports regarding the presence of PTHrP in CSF. DESIGN AND METHODS: PTHrP and Ca were quantified in paired CSF and serum samples using mass spectrometry-based methods. Associations between PTHrP and Ca concentrations with age, sex and concentrations of nine CSF diagnostic markers in a set of 140 paired serum and CSF patient samples were evaluated. RESULTS: The observed median PTHrP concentration in CSF was 51 times higher than in serum; the median concentration of Ca in CSF was 1.8 times lower than in serum. We observed positive correlation between concentrations of PTHrP in CSF and serum (p=0.013). Distribution of PTHrP concentrations in serum was associated with age (p=0.0068) and the concentrations were higher in women. In samples with serum calcium concentrations within the reference intervals (n=118), central 95% distribution of concentrations for Ca-CSF, PTHrP-serum and PTHrP-CSF were 5.4 (4.5-6.1) mg/dL, 1.2 (0.5-2.5) pmol/L, 62 (22-125) pmol/L, respectively. CONCLUSIONS: Our data demonstrate that PTHrP is a normal constituent of human CSF with median concentrations 51 fold higher than in serum. Elevated serum PTHrP concentrations were positively correlated with age and significantly higher in women. Our data suggest that CSF could be a significant source of circulating PTHrP.

An exploratory study Evaluating the impact of opioid and non-opioid pain medications on serum/plasma free testosterone and free estradiol concentrations.

Chronic use of opioid medications has been reported to cause altered sexual function. It is not known if non-opioid pain medications have similar effects. Assessment of this effect through the measurement of concentrations of free hormones is limited. Positivity of opioid medications (hydrocodone, oxycodone, morphine, methadone, tramadol and fentanyl) and non-opioid pain medications (gabapentin or pregabalin) in human serum and plasma samples from adult men and women were evaluated for association with concentrations of free testosterone (fTe) and free estradiol (fE2) measured using equilibrium dialysis-liquid chromatography-tandem mass spectrometry methods. Lower concentrations of fTe (p = 0.0253) were observed in samples positive for the hydrocodone, oxycodone and morphine group compared to age matched controls. The presence of methadone, tramadol, fentanyl and pregabalin had no effect on fTe. When compared with age-matched controls, women between 48-55 years of age showed reduced fE2 concentrations in samples positive for tramadol, fentanyl and gabapentin (p = 0.0243, 0.0045 and 0.0050, respectively). Particular opioid medications such as methadone, tramadol or fentanyl and non-opioid medications such as pregabalin or gabapentin may offer advantages over opioid medications for treating pain with fewer endocrinologic side effects. Measurement of free hormones in pain medication users could be important in determining their association with sexual function. Copyright © 2017 John Wiley & Sons, Ltd.

Changes in DHEA-s levels during the first year of treatment in patients with clinical burnout are related to health development.

The regenerative hormone DHEA-S was measured in 122 patients with clinical burnout during their first year of treatment. Relations between change of DHEA-S levels and development in health were investigated. About half of the patients exhibited increased DHEA-S levels during the year, while the other half exhibited decreased levels. There was no difference in burnout symptoms or associated health status at baseline between subsequent DHEA-S increasing and DHEA-S decreasing groups. Greater reduction in the burnout symptoms was observed in patients in who DHEA-S levels increased during the year, than in the patients in who DHEA-S levels decreased. Relative change of DHEA-S and direction of the change during the year both predicted burnout symptoms at the end of the year. In addition, patients with increased DHEA-S levels had better self-rated health, vitality and well-being. Our data suggest that changes in DHEA-S are associated with prognosis for the outcome in burnout patients.

Recommendations for the Generation, Quantification, Storage, and Handling of Peptides Used for Mass Spectrometry-Based Assays.

BACKGROUND: For many years, basic and clinical researchers have taken advantage of the analytical sensitivity and specificity afforded by mass spectrometry in the measurement of proteins. Clinical laboratories are now beginning to deploy these work flows as well. For assays that use proteolysis to generate peptides for protein quantification and characterization, synthetic stable isotope-labeled internal standard peptides are of central importance. No general recommendations are currently available surrounding the use of peptides in protein mass spectrometric assays. CONTENT: The Clinical Proteomic Tumor Analysis Consortium of the National Cancer Institute has collaborated with clinical laboratorians, peptide manufacturers, metrologists, representatives of the pharmaceutical industry, and other professionals to develop a consensus set of recommendations for peptide procurement, characterization, storage, and handling, as well as approaches to the interpretation of the data generated by mass spectrometric protein assays. Additionally, the importance of carefully characterized reference materials-in particular, peptide standards for the improved concordance of amino acid analysis methods across the industry-is highlighted. The alignment of practices around the use of peptides and the transparency of sample preparation protocols should allow for the harmonization of peptide and protein quantification in research and clinical care.

LC-MS/MS Measurement of Parathyroid Hormone-Related Peptide.

INTRODUCTION: Parathyroid hormone-related peptide (PTHrP) is involved in activating pathways, allowing tumor cells to form bone metastases. Measurement of PTHrP is used for the diagnosis and clinical management of patients suspected of hypercalcemia of malignancy. We developed an LC-MS/MS method for measuring PTHrP, established sex-specific reference intervals, and assessed the method's performance. METHODS: PTHrP was enriched from plasma samples with rabbit polyclonal anti-PTHrP antibody conjugated to magnetic beads. Enriched PTHrP was digested with trypsin, and PTHrP-specific tryptic peptide was analyzed with 2-dimensional LC-MS/MS in multiple reaction monitoring mode. RESULTS: The lower limit of quantification was 0.6 pmol/L, and the upper limit of linearity was 600 pmol/L. Total imprecision was <10%. Very poor agreement was observed with the RIA (n = 207; Deming regression RIA = 0.059 × LC-MS/MS - 1.8, r = 0.483; Sy|x = 3.9). Evaluation of the clinical performance of the assay using samples from patients with and without hypercalcemia (n = 199) resulted in an area under the ROC curve of 0.874. In sets of consecutively analyzed routine samples of patients assessed for hypercalcemia, the PTHrP positivity rate by RIA (n = 1376) was 1.9%, and 26.6% by LC-MS/MS (n = 1705). Concentrations were below the lower limit of quantification in 95.6% of the samples by RIA and 2.0% by LC-MS/MS. CONCLUSIONS: PTHrP is a normal constituent in circulating blood and its concentrations are substantially underestimated by commercial RIAs, causing false-negative results in samples from patients suspected of hypercalcemia. Our observations suggest a link between increased concentrations of PTHrP in postmenopausal women with low body mass index and increased incidence of osteoporosis.

Mass spectrometry methods measured androgen and estrogen concentrations during pregnancy and in newborns of mothers with polycystic ovary syndrome.

OBJECTIVE: Little is known about the aetiology of polycystic ovary syndrome (PCOS). Some suggest that elevated maternal androgens during gestation play a causative role. This implies placental passage of androgens during pregnancy. The aim of this study is to compare androgen and estrogen concentrations in maternal serum during pregnancy and in umbilical cord blood, between mothers with PCOS and their offspring compared to controls. DESIGN: Prospective case-control study. METHODS: Maternal blood samples were collected around 20 weeks of gestation and at delivery. Umbilical cord blood was also taken at delivery. Androgens (testosterone (T), androstenedione (ADION), dehydroepiandrostenedione (DHEA)) and estrogens (estrone (E1), estradiol (E2), estriol (E3)) were measured using the liquid chromatography tandem mass spectrometry (LC-MS/MS) methods. RESULTS: At 20 weeks of gestation: T (P=0.019) and ADION (P=0.034) were higher in the PCOS mothers (pregnant with a girl), whereas DHEA, E1, E2, and E3 were not different. Maternal concentration at birth: T (P=0.004) and ADION (P=0.009) were also higher in the subgroup of PCOS mothers that were pregnant with a girl compared to the girl pregnancy controls. DHEA, E1, E2 and E3 were not different. In umbilical cord blood, no differences were found for T, ADION, DHEA, E2, E3, and AMH between the PCOS mothers and the controls respectively. E1 was lower in girls from PCOS mothers (P=0.007). CONCLUSIONS: Despite elevated maternal androgen concentrations during pregnancy in PCOS mothers, offspring showed no signs of elevated androgen concentrations in cord blood at birth using the latest highly specific LC-MS/MS methods.