Given the reported correlation between cerebrospinal fluid (CSF) and salivary oxytocin concentrations, salivary oxytocin has been proposed as a promising peripheral biomarker of central oxytocin activity. To date, oxytocin levels are commonly measured using enzyme immunoassays or radio-immunoassays; however, several challenges related to its accurate quantification have been reported, underscoring the need for a standardized and reliable analytical method. The present study aimed to develop and validate a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the quantification of oxytocin in human saliva, in accordance with EMA and FDA guidelines for bioanalytical method validation. Oxytocin levels were determined using the standard addition method. The chromatographic separation was performed through a gradient elution of two mobile phases (H2O + 0.1% F.A. and MeOH: DMSO 97:3 (v/v) + 0.1% F.A.) using a Phenomenex Luna Omega 1.6 μm PS C18 100 Å LC Column 50 × 2.1 mm at 40°C with a column thermostat. It was connected to a tandem mass spectrometer, and the chromatographic run lasted 5 min. Additionally, in order to evaluate precision and accuracy of the method, real-world samples from caregivers working with people with dementia were analyzed. Method validation achieved satisfactory results in terms of robustness and reproducibility, especially at higher concentration values, while expected higher variability at lower concentrations was observed. However, real-world samples analysis confirmed the applicability of the method to real biological samples. Overall, the method was able to accurately quantify oxytocin levels in real-world samples, thus demonstrating its applicability in epidemiological studies.
Adolescence is marked by an increased frequency of conflict with parents and friends. Although conflict within these relationships has been linked to dysregulated hair cortisol concentration (HCC), the genetic and environmental mechanisms contributing to this association remain poorly understood. This study examined whether conflict with parents and friends during adolescence is associated with HCC and whether current conflicts interact with genetic and environmental contributions to cortisol levels, independently of past conflict. Participants were 158 Monozygotic and 248 Dizygotic twin pairs (54% girls; 86% Whites, 6% Blacks, 6% Asians, 0.3% Native North Americans). Relationship conflict with the mother, father, and best friend was measured through adolescents’ self-reports from ages 13–19 years (4 assessments), and hair samples were collected for cortisol measurement at age 19. Biometric modeling revealed no association between current or past conflict with either social agent and HCC. However, current conflict with the father reduced the strength of genetic influences on HCC, coinciding with a relative increase of environmental influences. Similar moderating effects were not detected for conflict with the mother or best friend. These findings suggest that, in adolescents experiencing higher levels of current father-youth conflict, the stress-regulatory mechanisms of the HPA axis may be especially susceptible to additional—either protective or aggravatingsources of environmental influence.
Maternal hypothalamic-pituitary-adrenal axis functioning has important implications for maternal and offspring health, yet findings on cortisol responsivity to acute stress during pregnancy are mixed. Further, little is known about how childhood stress exposure relates to physiological stress regulation during this period, particularly among Black and White women. The present study leveraged multiple waves of prospectively gathered data from a large population-based sample to examine associations between degree of exposure to subsistence-, safety- and caregiving-related stress across childhood and cortisol responsivity during a later pregnancy. Participants (N = 338, 69.7% Black, 26.7% White) were enrolled in the longitudinal Pittsburgh Girls Study in middle childhood. Caregivers reported annually on exposure to a range of stressors when participants were 7–17 years of age. During a prenatal laboratory visit in which participants were between 22 and 31 years of age, participants completed the Trier Social Stress Test (TSST) and provided saliva samples for cortisol assay. Adjusting for covariates, the TSST did not produce a significant increase in cortisol levels over time, though 28.3% of participants were classified as responders. Greater exposure to subsistence-related stress (e.g., resource strain, housing instability) across childhood was associated with blunted cortisol levels during pregnancy. Findings suggest that childhood exposure to subsistence-related stress may have enduring effects on physiological stress regulation and underscore the potential value of targeted preventive interventions to promote intergenerational health. Results also highlight the relevance of public health initiatives aimed at reducing population-level differences in subsistence-related stress exposure.
Background Fatigue is amongst the most debilitating cancer-related symptoms, affecting up to one-third of colorectal cancer (CRC) survivors. Accumulating evidence implicates dysregulation of HPA axis as a potential mechanism contributing to chronic fatigue syndrome. We examined longitudinal associations between parameters of diurnal cortisol rhythms and fatigue in CRC survivors up to 12 months after treatment. Methods Seventy-four survivors of CRC were assessed at 6 weeks, 6 months and 12 months after treatment. At each point, salivary samples were collected five times per day over two consecutive days to measure cortisol concentrations. Relative amplitude (RA), diurnal slope, area under the curve (AUCg) and cortisol awakening response (CAR) were derived as a comprehensive assessment of diurnal cortisol rhythms. Fatigue was assessed at all time points using the Checklist Individual Strength (CIS; range overall score: 20–140; motivational subscale: 4–28) and the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC; range: 0–100). Longitudinal associations were analyzed using confounder-adjusted linear mixed models, with coefficients (β) indicating differences in fatigue scores over time per SD increase in cortisol parameters. Results A higher RA was associated with less overall fatigue (EORTC: β= -1.42; 95%CI: -2.82, -0.03; CIS: β= -1.82; 95%CI: -3.63, -0.01). A flatter diurnal slope, indicating less decline in cortisol over the day, was associated with more fatigue (EORTC: β=1.64; 0.25, 3.03) and increased motivational fatigue (CIS: β= 0.45; 0.02, 0.88). Conclusion More pronounced diurnal cortisol rhythms, specifically a higher RA and steeper diurnal slope, were longitudinally associated with less fatigue in CRC survivors. These findings may suggest that improving 24-h cortisol rhythmicity could be a target for interventions to reduce fatigue in CRC survivors, but this warrants further investigations.
