Assays that measure steroid hormones in patient care, public health, and research need to be both accurate and precise, as these criteria help to ensure comparability across all clinical and research ...applications. This review addresses major issues relevant to assay variability and describes recent activities by the US Centers for Disease Control and Prevention (CDC) to improve assay performance. Currently, high degrees of accuracy and precision are not always met for testosterone and estradiol measurements; although technologies for steroid hormone measurement have advanced significantly, measurement variability within and across laboratories has not improved accordingly. Differences in calibration and specificity are discussed as sources of variability in measurement accuracy. Ultimately, a combination of factors appears to cause inaccuracy of steroid hormone measurements, with nonuniform assay calibration and lack of specificity being two major contributors to assay variability. Within-assay variability for current assays is generally high, especially at low analyte concentrations. The CDC Hormone Standardization (HoSt) Program is improving clinical assays, as evidenced by a 50% decline in mean absolute bias between mass spectrometry assays and the CDC reference method from 2007 to 2011. This program provides the measurement traceability to CDC reference methods and helps to minimize factors affecting measurement variability.
The inaccuracy of routine serum 25-hydroxyvitamin D measurements hampers the interpretation of data in patient care and public health research. We developed and validated a candidate reference ...measurement procedure (RMP) for highly accurate quantitation of two clinically important 25-hydroxyvitamin D metabolites in serum, 25-hydroxyvitamin D₂ 25(OH)D₂ and 25-hydroxyvitamin D₃ 25(OH)D₃. The two compounds of interest together with spiked deuterium-labeled internal standards d ₃-25(OH)D₂ and d ₆-25(OH)D₃ were extracted from serum via liquid-liquid extraction. The featured isotope-dilution LC-MS/MS method used reversed-phase chromatography and atmospheric pressure chemical ionization in positive ion mode. A pentafluorophenylpropyl-packed UHPLC column together with isocratic elution allowed for complete baseline resolution of 25(OH)D₂ and 25(OH)D₃ from their structural C-3 isomers within 12 min. We evaluated method trueness, precision, potential interferences, matrix effects, limits of quantitation, and measurement uncertainty. Calibration materials were, or were traceable to, NIST Standard Reference Materials 2972. Within-day and total imprecision (CV) averaged 1.9 and 2.0 % for 25(OH)D₃, respectively, and 2.4 and 3.5 % for 25(OH)D₂, respectively. Mean trueness was 100.3 % for 25(OH)D₃ and 25(OH)D₂. The limits of quantitation/limits of detection were 4.61/1.38 nmol/L for 25(OH)D₃ and 1.46/0.13 nmol/L for 25(OH)D₂. When we compared our RMP results to an established RMP using 40 serum samples, we found a nonsignificant mean bias of 0.2 % for total 25(OH)D. This candidate RMP for 25(OH)D metabolites meets predefined method performance specifications (≤5 % total CV and ≤1.7 % bias) and provides sufficient sample throughput to meet the needs of the Centers for Disease Control and Prevention Vitamin D Standardization Certification Program.
High mammographic density is among the strongest and most established predictors for breast cancer risk. Puberty, the period during which breasts undergo exponential mammary growth, is considered one ...of the critical stages of breast development for environmental exposures. Benzylbutyl phthalate (BBP) and perfluorooctanoic acid (PFOA) are pervasive endocrine disrupting chemicals that may increase hormone-sensitive cancers. Evaluating the potential impact of BBP and PFOA exposure on pubertal breast density is important to our understanding of early-life environmental influences on breast cancer etiology.
To prospectively assess the effect of biomarker concentrations of monobenzyl phthalate (MBzP) and PFOA at specific pubertal window of susceptibility (WOS) on adolescent breast density.
This study included 376 Chilean girls from the Growth and Obesity Cohort Study with data collection at four time points: Tanner breast stages 1 (B1) and 4 (B4), 1- year post menarche (1YPM) and 2-years post menarche (2YPM). Dual-energy X-ray absorptiometry was used to assess the absolute fibroglandular volume (FGV) and percent breast density (%FGV) at 2YPM. We used concentrations of PFOA in serum and MBzP in urine as an index of exposure to PFOA and BBP, respectively. Parametric G-formula was used to estimate the time-specific effects of MBzP and PFOA on breast density. The models included body fat percentage as a time-varying confounder and age, birthweight, age of menarche, and maternal education as fixed covariates.
A doubling of serum PFOA concentration at B4 resulted in a non-significant increase in absolute FGV (β:11.25, 95% confidence interval (CI): -0.28, 23.49)), while a doubling of PFOA concentration at 1YPM resulted in a decrease in % FGV (β:-4.61, 95% CI: -7.45, -1.78). We observed no associations between urine MBzP and breast density measures.
In this cohort of Latina girls, PFOA serum concentrations corresponded to a decrease in % FGV. No effect was observed between MBzP and breast density measures across pubertal WOS.
Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent endocrine-disrupting chemicals associated with long-term health outcomes. PFAS are transferred from maternal blood to human ...milk, an important exposure source for infants, and understanding of this transfer is evolving. We characterized concentrations of 10 PFAS in human milk (n = 426) and compared milk-to-plasma concentrations of 9 PFAS among a subset of women with paired samples (n = 294) from the New Hampshire Birth Cohort Study using liquid chromatography-isotope dilution tandem mass spectrometry. We examined the relationship between perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in plasma versus milk and fit linear regression models to assess relationships between milk PFOA and PFOS and participant characteristics. The median plasma PFOA concentration was 0.94 ng/mL (interquartile range, IQR, 0.59–1.34) and that of PFOS was 2.60 ng/mL (IQR 1.80–3.90); the median milk PFOA concentration was 0.017 ng/mL (IQR 0.012–0.027) and that of PFOS was 0.024 ng/mL (IQR 0.016–0.036). PFOA and PFOS plasma and milk concentrations showed correlations of ρ = 0.83 and 0.77, respectively (p < 0.001). Parity, previous lactation, week of milk collection, and body mass index were inversely associated with milk PFAS. We estimate that even among our general population cohort, some infants (∼6.5%) are exposed to amounts of PFAS via milk that may have long-term health impacts.
Concerns are heightened from detecting environmentally persistent man-made per- and polyfluoroalkyl substances (PFAS) in drinking water systems around the world. Many PFAS, including perfluorooctane ...sulfonate (PFOS) and perfluorooctanoate (PFOA), remain in the human body for years. Since 1999–2000, assessment of exposure to PFOS, PFOA, and other select PFAS in the U.S. general population has relied on measuring PFAS serum concentrations in participants of the National Health and Nutrition Examination Survey (NHANES). Manufacturers have replaced select chemistries (“legacy” PFAS) with PFAS with shorter biological half-lives (e.g., GenX, perfluorobutanoate PFBA) which may efficiently eliminate in urine. However, knowledge regarding exposure to these compounds is limited. We analyzed 2682 urine samples for 17 legacy and alternative PFAS in 2013–2014 NHANES participants ≥6 years of age. Concentrations of some of these PFAS, measured previously in paired serum samples from the same NHANES participants, suggested universal exposure to PFOS and PFOA, and infrequent or no exposure to two short-chain PFAS, perfluorobutane sulfonate and perfluoroheptanoate. Yet, in urine, PFAS were seldom detected; the frequency of not having detectable concentrations of any of the 17 PFAS was 67.5%. Only two were detected in >1.5% of the population: PFBA (13.3%) and perfluorohexanoate (PFHxA, 22.6%); the 90th percentile urine concentrations were 0.1 μg/L (PFBA), and 0.3 μg/L (PFHxA). These results suggest that exposures to short-chain PFAS are infrequent or at levels below those that would result in detectable concentrations in urine. As such, these findings do not support biomonitoring of short-chain PFAS or fluorinated alternatives in the general population using urine, and highlight the importance of selecting the adequate biomonitoring matrix.
•No detectable extensive exposure to alternative PFAS in the U.S. general population•Choice of matrix influences the success of biomonitoring exposure assessments•Serum levels are best for biomonitoring of PFAS regardless of their biopersistence
Abstract
Context
Epidemiologic studies have demonstrated that overweight/obese girls (OW/OB) undergo thelarche and menarche earlier than normal weight girls (NW). There have been no longitudinal ...studies to specifically investigate how body weight/fat affects both clinical and biochemical pubertal markers in girls.
Objective
To investigate the effect of total body fat on reproductive hormones and on the maturation of estrogen-sensitive tissues during puberty in girls.
Methods
Ninety girls (36 OW/OB, 54 NW), aged 8.2 to 14.7 years, completed 2.8 ± 1.7 study visits over 4 years. Visits included dual-energy x-ray absorptiometry to calculate total body fat (TBF), Tanner staging, breast ultrasound for morphological staging (BMORPH; A-E), pelvic ultrasound, hormone tests, and assessment of menarchal status. The effect of TBF on pubertal markers was determined using a mixed, multistate, or Cox proportional hazards model, controlling for baseline BMORPH.
Results
NW were older than OW/OB (11.3 vs 10.2 years, P < .01) at baseline and had more advanced BMORPH (P < .01). Luteinizing hormone, estradiol, and ovarian and uterine volumes increased with time with no effect of TBF. There was a time × TBF interaction for follicle-stimulating hormone, inhibin B, estrone, total and free testosterone, and androstenedione: Levels were initially similar, but after 1 year, levels increased in girls with higher TBF, plateaued in girls with midrange TBF, and decreased in girls with lower TBF. Girls with higher TBF progressed through BMORPH stage D more slowly but achieved menarche earlier than girls with lower TBF.
Conclusion
In late puberty, girls with higher TBF demonstrate differences in standard hormonal and clinical markers of puberty. Investigation of the underlying causes and clinical consequences of these differences in girls with higher TBF deserves further study.
Previous studies have examined the predictors of PFAS concentrations among pregnant women and children. However, no study has explored the predictors of preconception PFAS concentrations among ...couples in the United States. This study included 572 females and 279 males (249 couples) who attended a U.S. fertility clinic between 2005 and 2019. Questionnaire information on demographics, reproductive history, and lifestyles and serum samples quantified for PFAS concentrations were collected at study enrollment. We examined the PFAS distribution and correlation within couples. We used Ridge regressions to predict the serum concentration of each PFAS in females and males using data of (1) socio-demographic and reproductive history, (2) diet, (3) behavioral factors, and (4) all factors included in (1) to (3) after accounting for temporal exposure trends. We used general linear models for univariate association of each factor with the PFAS concentration. We found moderate to high correlations for PFAS concentrations within couples. Among all examined factors, diet explained more of the variation in PFAS concentrations (1–48%), while behavioral factors explained the least (0–4%). Individuals reporting White race, with a higher body mass index, and nulliparous women had higher PFAS concentrations than others. Fish and shellfish consumption was positively associated with PFAS concentrations among both females and males, while intake of beans (females), peas (male), kale (females), and tortilla (both) was inversely associated with PFAS concentrations. Our findings provide important data for identifying sources of couples’ PFAS exposure and informing interventions to reduce PFAS exposure in the preconception period.
Prenatal per and polyfluoroalkyl substances (PFAS) exposure is associated with adverse birth outcomes. There is an absence of evidence on the relationship between maternal and paternal preconception ...PFAS exposure and birth outcomes. This study included 312 mothers and 145 fathers with a singleton live birth from a preconception cohort of subfertile couples seeking fertility treatment at a U.S. clinic. PFAS were quantified in serum samples collected before conception. Gestational age (GA) and birthweight (BW) were abstracted from delivery records. We also assessed low birthweight (BW < 2500 g) and preterm birth (GA < 37 completed weeks). We utilized multivariable linear regression, logistic regression, and quantile-based g computation to examine maternal or paternal serum concentrations of individual PFAS and mixture with birth outcomes. Maternal serum concentrations of perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate (PFHxS), and the total PFAS mixture were inversely associated with birthweight. Maternal PFOS concentration was associated with a higher risk of low birthweight. Conversely, paternal PFOS and PFHxS concentrations were imprecisely associated with higher birthweight. No associations were found for gestational age or preterm birth. The findings have important implications for preconception care. Future research with larger sample sizes would assist in validating these findings.
Black women are exposed to multiple endocrine-disrupting chemicals (EDCs), but few studies have examined their profiles of exposure to EDC mixtures. We identified biomarker profiles and correlates of ...exposure to EDC mixtures in a cross-sectional analysis of data from a prospective cohort study of 749 Black women aged 23–35 years. We quantified plasma concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs), and per- and polyfluoroalkyl substances (PFAS) in nonfasting samples collected at baseline. Demographic, behavioral, dietary, and reproductive covariates were also collected at baseline. We used k-means clustering and principal component analysis (PCA) to describe concentration profiles of EDC mixtures (17 PCBs, 6 PBDEs, 4 OCPs, 6 PFAS), followed by multinomial logistic and multivariable linear regression to estimate mean differences in PCA scores (β) and odds ratios (ORs) of cluster membership with their respective 95% confidence intervals (CIs). Older age (per 1 year increase: β = 0.47, CI = 0.39, 0.54; OR = 1.27, CI = 1.20, 1.35), lower body mass index (per 1 kg/m2 increase: β = −0.14, CI = −0.17, −0.12; OR = 0.91, CI = 0.89, 0.94), and current smoking (≥10 cigarettes/day vs never smokers: β = 1.37, CI = 0.20, 2.55; OR = 2.63, CI = 1.07, 6.50) were associated with profiles characterized by higher concentrations of all EDCs. Other behaviors and traits, including dietary factors and years since last birth, were also associated with EDC mixtures.
Pregnant persons are exposed ubiquitously to phthalates and increasingly to chemicals introduced to replace phthalates. In early pregnancy, exposure to these chemicals may disrupt fetal formation and ...development, manifesting adverse fetal growth. Previous studies examining the consequences of early pregnancy exposure relied on single spot urine measures and did not investigate replacement chemicals.
Characterize associations between urinary phthalate and replacement biomarkers in early pregnancy and fetal growth outcomes.
Analyses were conducted among 254 pregnancies in the Human Placenta and Phthalates Study, a prospective cohort with recruitment 2017–2020. Exposures were geometric mean concentrations of phthalate and replacement biomarkers quantified in two spot urine samples collected around 12- and 14-weeks of gestation. Outcomes were fetal ultrasound biometry (head and abdominal circumferences, femur length, estimated fetal weight) collected in each trimester and converted to z-scores. Adjusted linear mixed effects (single-pollutant) and quantile g-computation (mixture) models with participant-specific random effects estimated the difference, on average, in longitudinal fetal growth for a one-interquartile range (IQR) increase in individual (single-pollutant) or all (mixture) early pregnancy phthalate and replacement biomarkers.
Mono carboxyisononyl phthalate and the sums of metabolites of di-n-butyl, di-iso-butyl, and di-2-ethylhexyl phthalate were inversely associated with fetal head and abdominal circumference z-scores. A one-IQR increase in the phthalate and replacement biomarker mixture was inversely associated with fetal head circumference (β: -0.36 95% confidence interval: -0.56, −0.15) and abdominal circumference (−0.31 -0.49, −0.12) z-scores. This association was mainly driven by phthalate biomarkers.
Urine concentrations of phthalate biomarkers, but not replacement biomarkers, in early pregnancy were associated with reductions in fetal growth. Though the clinical implications of these differences are unclear, reduced fetal growth contributes to excess morbidity and mortality across the lifecourse. Given widespread global exposure to phthalates, findings suggest a substantial population health burden resulting from early pregnancy phthalate exposure.
•Exposure to potentially harmful consumer product chemicals is ubiquitous.•Susceptibility to these chemicals may be increased in early pregnancy.•Early pregnancy phthalate exposure was associated with reduced fetal growth.•Associations were strongest for fetal growth outcomes in late pregnancy.•Replacements DEHTP and DINCH were not associated with fetal growth.
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