Time-resolved immunofluorometric assays for urinary luteinizing hormone and follicle stimulating hormone

Polybrominated Biphenyl Exposure and Menstrual Cycle Function

BACKGROUND

Brominated flame retardants, including polybrominated biphenyls (PBB), are persistent compounds reported to affect sex hormones in animals; less is known about potential effects in humans. An industrial accident in 1973-1974 exposed Michigan residents to PBB through contaminated food. We examined whether this exposure to PBB had long-term effects on menstrual cycle function.

METHODS

In 2004-2006, we recruited reproductive-aged women in the Michigan PBB Registry who were not pregnant, lactating, or taking hormonal medications. Participants kept daily diaries and provided daily urine samples for up to 6 months. We assayed the urine samples for estrone 3-glucuronide (E13G), pregnanediol 3-glucuronide (Pd3G), and follicle stimulating hormone (FSH). We fit linear mixed models among women aged 35-42 years to describe the relation between serum PBB levels and log-transformed, creatinine-adjusted daily endocrine levels among women who were premenarchal during the exposure incident in 1973-1974 (n = 70).

RESULTS

We observed that high (>3.0 parts per billion [ppb]) and medium (>1.0-3.0 ppb) PBB exposure were associated with lower E13G levels across the menstrual cycle and lower FSH levels during the follicular phase, compared with low PBB exposure (≤1.0 ppb). High PBB exposure was also associated with lower Pd3G levels across the cycle compared with low PBB exposure, whereas Pd3G levels were similar in women with medium and low PBB exposure.

CONCLUSION

Our results are consistent with a hypothesized effect of exposure to an exogenous estrogen agonist but the modest sample size of the study requires cautious interpretation.

Thyroid hormones and menstrual cycle function in a longitudinal cohort of premenopausal women

BACKGROUND

Previous studies have reported that hyperthyroid and hypothyroid women experience menstrual irregularities more often compared with euthyroid women, but reasons for this are not well-understood and studies on thyroid hormones among euthyroid women are lacking. In a prospective cohort study of euthyroid women, this study characterised the relationship between thyroid hormone concentrations and prospectively collected menstrual function outcomes.

METHODS

Between 2004-2014, 86 euthyroid premenopausal women not lactating or taking hormonal medications participated in a study measuring menstrual function. Serum thyroid hormones were measured before the menstrual function study began. Women then collected first morning urine voids and completed daily bleeding diaries every day for three cycles. Urinary oestrogen and progesterone metabolites (estrone 3-glucuronide (E₁ 3G) and pregnanediol 3-glucuronide (Pd3G)) and follicle-stimulating hormone were measured and adjusted for creatinine (Cr).

RESULTS

Total thyroxine (T₄ ) concentrations were positively associated with Pd3G and E₁ 3G. Women with higher (vs lower) T₄ had greater luteal phase maximum Pd3G (Pd3G = 11.7 μg/mg Cr for women with high T₄ vs Pd3G = 9.5 and 8.1 μg/mg Cr for women with medium and low T₄ , respectively) and greater follicular phase maximum E₁ 3G (E₁ 3G = 41.7 ng/mg Cr for women with high T₄ vs E₁ 3G = 34.3 and 33.7 ng/mg Cr for women with medium and low T₄ , respectively).

CONCLUSIONS

Circulating thyroid hormone concentrations were associated with subtle differences in menstrual cycle function outcomes, particularly sex steroid hormone levels in healthy women. Results contribute to the understanding of the relationship between thyroid function and the menstrual cycle, and may have implications for fertility and chronic disease.

Herbicides and adjuvants: an evolving view

The present report examines the in vitro genotoxicity (micronucleus assay) of herbicides and adjuvants and reports on an in vivo human study on potential endocrine effects of pesticides, including herbicides. Adjuvants are used in conjunction with 2,4-dichlorophenoxy acetic acid (2,4-D) and other herbicides. Earlier pesticide applier survey results ( n = 709) show that 59% of the applicators used adjuvants, and the majority of this group used paraffinic oils and/or surfactant mixtures. As a beginning effort to explore the role of adjuvants and herbicides in hormonally based reproductive effects, a prospective, controlled study was performed to analyze blood specimens from three different exposure groups (applicators using herbicides only; applicators using both herbicides and insecticides; and applicators using fumigants in addition to herbicides and insecticides; and a control group composed of other agricultural workers including organic farmers). The applicators and controls were age- and smoking-matched. Study subjects ( n = 78) were tested before, during, and after completion of pesticide application season for the effects of pesticide products on hormone levels in the bloodstream. Of the applicator exposure groups examined, only the herbicide group showed significant endocrinologic differences from controls. Free testosterone levels were significantly elevated in post-season measurements ( p = 0.032), and follicle-stimulating hormone (FSH) was significantly decreased at the height of the season ( p = 0.016) and in the post-season ( p = 0.010) as compared to controls. These endocrinologic findings are discussed in terms of their possible relationship to potential endocrine effects of herbicides, herbicide contaminants, and adjuvants. In vitro genotoxicity examination compared four different commercially available surfactant mixtures with 12 different commercial herbicide products, including six different chlorophenoxy herbicides. Only one herbicide yielded a significant dose-response curve. All four adjuvants showed positive dose-response effects. These preliminary data suggest that adjuvants are not inert but are toxicologically active components added to herbicide mixtures. Whether adjuvant toxicant effects are additive or are independent of herbicide effects is poorly understood.

Luteinizing Hormone in Premenopausal Women May Stimulate Uterine Leiomyomata Development

OBJECTIVE

Human chorionic gonadotropin (hCG) has proliferative effects on uterine smooth muscle and leiomyoma tissue in vitro. We hypothesized that luteinizing hormone (LH) would have the same effect by activating the LH/hCG receptor, and it would follow that premenopausal women with higher basal LH levels would be more likely to have leiomyomata.

METHODS

Randomly selected women, aged 35 to 49 years, from a prepaid health plan were screened for leiomyomata with pelvic ultrasound. Urine samples collected during the first or last 5 days of the menstrual cycle were analyzed for LH by immunofluorometric assay, and concentrations were corrected for creatinine (n = 523). Logistic regression and Bayes analyses were used to evaluate the association of LH with presence and size of leiomyomata, adjusting for age, and other risk factors.

RESULTS

Women with higher LH were more likely to have leiomyomata (adjusted odds ratios for second and third tertiles were 1.7 and 2.0 compared with lower tertile; 95% confidence intervals, 1.0 to 2.7 and 1.2 to 3.4, respectively). The association was stronger for large leiomyomata. Bayes analyses designed to estimate LH effects on tumor onset separately from tumor growth showed significantly accelerated tumor onset but little evidence of effects on tumor growth. Age, an independent risk factor for leiomyomata, was not affected by inclusion of LH in the logistic models.

CONCLUSIONS

As hypothesized, women with higher LH were more likely to have leiomyomata, but this did not explain the age-related increase in leiomyomata during perimenopausal ages. Determining whether LH is causal or a marker for susceptibility will require further research.

Menstrual cycle perturbation by organohalogens and elements in the Cree of James Bay, Canada

Persistent organohalogens (POHs) and metals have been linked to alterations in menstrual cycle function and fertility in humans. The Cree First Nations people living near James Bay in Ontario and Quebec, Canada, have elevated levels of POHs, mercury and lead compared to other Canadians. The present study examines the interrelationships between selected POHs and elements on menstrual cycle function in these Cree women. Menstrual cycle characteristics were derived from structured daily diaries and endocrine measurements from daily urine samples collected during one cycle for 42 women age 19-42. We measured 31 POHs in blood plasma and 18 elements in whole blood, for 31 of the participants. POHs and elements detected in ≥ 70% of the participants were transformed by principal component (PC) analysis to reduce the contaminant exposure data to fewer, uncorrelated PCA variables. Multiple regression analysis revealed that, after adjusting for confounders, PC-3 values showed significant negative association with cycle length, after adjusting for confounders (p = 0.002). PC-3 accounted for 9.2% of the variance and shows positive loadings for cadmium, selenium, and PBDE congeners 47 and 153, and a negative loading for copper. Sensitivity analysis of the model to quantify likely effect sizes showed a range of menstrual cycle length from 25.3 to 28.3 days using the lower and upper 95% confidence limits of mean measured contaminant concentrations to predict cycle length. Our observations support the hypothesis that the menstrual cycle function of these women may be altered by exposure to POHs and elements from their environment.

Association between serum 25-hydroxyvitamin D and ovarian reserve in premenopausal women

OBJECTIVE

Vitamin D has been linked to antimüllerian hormone levels, suggesting a possible association with greater ovarian reserve, but large population-based studies are lacking. Our objective was to explore the association between vitamin D and follicle-stimulating hormone (FSH) in premenopausal women.

METHODS

The Uterine Fibroid Study (1996-1999) enrolled randomly selected 30- to 49-year-old members of a Washington, DC, health plan (N = 1,430). Women provided blood and urine samples in addition to questionnaire data. The vitamin D metabolite 25-hydroxyvitamin D (25(OH)D) was measured in stored plasma samples. Urinary FSH (mIU/mg creatinine) was measured by immunofluorometric assay. To obtain baseline measures, we limited this investigation to urine samples collected in the first 5 days of the menstrual cycle or 5 days before menses onset. In addition, postmenopausal women and women using oral contraceptives were excluded, leaving 527 women for analysis. FSH was creatinine-adjusted, normalized by log transformation, and modeled with multivariable linear regression.

RESULTS

The median 25(OH)D level was 12 ng/mL, with approximately 75% of participants below the recommended level of 20 ng/mL. FSH and 25(OH)D were inversely related. For every 10-ng/mL increase in 25(OH)D, urinary FSH decreased by 14% (95% CI, -23 to -5; P = 0.003).

CONCLUSIONS

Vitamin D is inversely related to FSH. This is consistent with literature relating low vitamin D levels to lower antimüllerian hormone levels. Prospective studies should investigate whether low vitamin D levels contribute to decreased ovarian reserve.

Urinary follicle-stimulating hormone as a measure of natural fertility in a community cohort

High serum follicle-stimulating hormone (FSH) levels have been associated with diminished ovarian reserve; however, the association between high urinary FSH and reduced natural fertility has yet to be established. We sought to characterize the relationship between a single or multiple measurements of early follicular phase urinary FSH and fertility. Women (n = 209), 30 to 44 years old with no history of infertility, who had been trying to conceive for less than 3 months, provided early follicular phase urine. Participants subsequently kept a diary to record bleeding and intercourse and conducted standardized pregnancy testing for up to 6 months. A subset of women (N = 95) collected urine on cycle day 3 for up to 6 cycles. Urine was analyzed for FSH and creatinine (cr) corrected. Proportional hazard models were used to calculate fecundability ratios (FRs). Urinary FSH levels across cycles from the same woman were highly correlated (adjusted intraclass correlation = .77); within-woman variance was 3-fold lower than variance among women. Women with an initial urinary FSH level <7 mIU/mg cr exhibited a nonsignificant reduction in the probability of pregnancy (adjusted FR 0.71, 95% confidence interval [CI]: 0.45-1.13), as did women with elevated urinary FSH (≥12 mIU/mg cr; adjusted FR 0.78, 95% CI: 0.46-1.32). Using the most recent or maximum urinary FSH value did not strengthen the association. In the general population, urinary FSH levels appear to be nonlinearly associated with fertility; however, broad CIs indicate a lack of statistical significance. Repetitive testing appears to be of little benefit.

Antimüllerian hormone as a predictor of natural fecundability in women aged 30-42 years

OBJECTIVE

To generate estimates of the association between markers of ovarian aging and natural fertility in a community sample at risk for ovarian aging.

METHODS

Women aged 30-44 years with no history of infertility who had been trying to conceive for less than 3 months provided early-follicular phase serum and urine (N=100). Subsequently, these women kept a diary to record menstrual bleeding and intercourse and conducted standardized pregnancy testing for up to 6 months. Serum was analyzed for estradiol, follicle-stimulating hormone (FSH), antimüllerian hormone, and inhibin B. Urine was analyzed for FSH and estrone 3-glucuronide. Diary data on menstrual cycle day and patterns of intercourse were used to calculate day-specific fecundability ratios.

RESULTS

Sixty-three percent of participants conceived within 6 months. After adjusting for age, 18 women (18%) with serum antimüllerian hormone levels of 0.7 ng/mL or less had significantly reduced fecundability given intercourse on a fertile day compared with women with higher antimüllerian hormone levels (fecundability ratio 0.38; 95% confidence interval [CI] 0.08-0.91). The day-specific fecundability for women with early-follicular phase serum FSH values greater than 10 milli-international units/mL compared with women with lower FSH levels was also reduced, although nonsignificantly (11% of women affected; fecundability ratio 0.44; 95% CI 0.08-1.10). The association with urinary FSH was weaker (27% women affected; fecundability ratio 0.61; 95% CI 0.26-1.26), and the associations for the other markers were weaker still.

CONCLUSION

Early-follicular phase antimüllerian hormone appears to be associated with natural fertility in the general population.

LEVEL OF EVIDENCE

II.

Menstrual cycle characteristics and reproductive hormone levels in women exposed to atrazine in drinking water

Atrazine is the most commonly used herbicide in the U.S. and a wide-spread groundwater contaminant. Epidemiologic and laboratory evidence exists that atrazine disrupts reproductive health and hormone secretion. We examined the relationship between exposure to atrazine in drinking water and menstrual cycle function including reproductive hormone levels. Women 18-40 years old residing in agricultural communities where atrazine is used extensively (Illinois) and sparingly (Vermont) answered a questionnaire (n=102), maintained menstrual cycle diaries (n=67), and provided daily urine samples for analyses of luteinizing hormone (LH), and estradiol and progesterone metabolites (n=35). Markers of exposures included state of residence, atrazine and chlorotriazine concentrations in tap water, municipal water and urine, and estimated dose from water consumption. Women who lived in Illinois were more likely to report menstrual cycle length irregularity (odds ratio (OR)=4.69; 95% confidence interval (CI): 1.58-13.95) and more than 6 weeks between periods (OR=6.16; 95% CI: 1.29-29.38) than those who lived in Vermont. Consumption of >2 cups of unfiltered Illinois water daily was associated with increased risk of irregular periods (OR=5.73; 95% CI: 1.58-20.77). Estimated "dose" of atrazine and chlorotriazine from tap water was inversely related to mean mid-luteal estradiol metabolite. Atrazine "dose" from municipal concentrations was directly related to follicular phase length and inversely related to mean mid-luteal progesterone metabolite levels. We present preliminary evidence that atrazine exposure, at levels below the US EPA MCL, is associated with increased menstrual cycle irregularity, longer follicular phases, and decreased levels of menstrual cycle endocrine biomarkers of infertile ovulatory cycles.

Effects of early pregnancy loss on hormone levels in the subsequent menstrual cycle

Previous studies of hormone patterns after clinical miscarriage suggest reduced pituitary function. Hormonal effects of very early pregnancy loss (before 6 weeks gestation) have not been described. We used within-woman differences between menstrual cycles in urinary hormone measurements from women in the North Carolina Early Pregnancy Study to describe hormonal changes after very early pregnancy loss (n = 28 early losses; 80 non-conception comparison cycles). We found lower pre-ovulatory luteinising hormone and shorter luteal phase length after very early pregnancy loss, but the differences were non-significant (p > 0.3) and smaller than those reported in the spontaneous miscarriage literature. Consistent with the reduced pituitary function reported post-spontaneous miscarriage, we found a slower rate of oestrogen rise (p = 0.08). There was no evidence of lower mid-luteal steroid levels as has been suggested for post-spontaneous miscarriage cycles. Very early pregnancy losses do not appear to influence subsequent menstrual cycles to the same degree as spontaneous miscarriages.

Mother's menopausal age is associated with her daughter's early follicular phase urinary follicle-stimulating hormone level

OBJECTIVE

Early follicular phase follicle-stimulating hormone (FSH), a marker of ovarian reserve, has been used to predict time to menopause. A mother's age at menopause is related to her daughter's age at menopause, possibly because of genetic factors. In this study we sought to determine the relationship between maternal age at menopause and early follicular phase FSH of premenopausal daughters.

DESIGN

The Uterine Fibroid Study enrolled women randomly selected from a prepaid health plan, collected questionnaire data, and obtained early follicular phase urine samples for a subset of participants. For this secondary analysis, premenopausal women between the ages of 35 and 46 years, who provided a urine sample on cycle day 2, 3, 4, or 5 and their mother's age at natural menopause (n = 182) were selected from the original cohort. Initially bivariate analysis and subsequently regression modeling were performed to assess the independent relationship between maternal age at menopause and urinary creatinine-corrected FSH.

RESULTS

Unadjusted analyses and those adjusting for age (mean +/- SD, 40.5 +/- 3.2 y), smoking status (16% current smokers), and body mass index (26.8 +/- 6.9 kg/m) showed a significant association between maternal age at menopause and daughter's urinary FSH level (P < 0.04). Women whose mothers experienced earlier menopause had higher urinary FSH levels.

CONCLUSIONS

The significantly increased FSH values among women whose mothers experienced early menopause is consistent with previously reported associations between mother's and daughter's age of menopause. FSH, a marker of ovarian reserve, is influenced by both genetic and environmental factors. Future epidemiologic studies on FSH should include collection of information on maternal age at menopause.

Male reproductive hormones and thyroid function in pesticide applicators in the Red River Valley of Minnesota

In the present effort, 144 pesticide applicators and 49 urban control subjects who reported no chronic disease were studied. Applicators provided records of the season's pesticides used by product, volumes, dates, and methods of application. Blood specimens for examination of hormone levels were obtained in summer and fall. In the herbicide-only applicator group, significant increases in testosterone levels in fall compared to summer and also elevated levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the fall were noted. With respect to fungicide use, in an earlier cross-sectional epidemiologic study, data demonstrated that historic fungicide use was associated with a significant alteration of the sex ratio of children borne to applicators. As before, among current study subjects it was noted that historic fungicide use was associated with increased numbers of girls being born. Lower mean total testosterone concentrations by quartile were also correlated with increased numbers of live-born female infants. A downward summer to fall seasonal shift in thyroid-stimulating hormone (TSH) concentrations occurred among applicators but not among controls. Farmers who had aerial application of fungicides to their land in the current season showed a significant shift in TSH values (from 1.75 to 1.11 mU/L). Subclinical hypothyroidism was noted in 5/144 applicators (TSH values >4.5 mU/L), but not in urban control subjects. Based on current and past studies, it was concluded that, in addition to pesticide exposure, individual susceptibility and perhaps economic factors may play a supporting role in the reported results.

Feasibility issues in reproductive biomonitoring of female flight attendants and teachers

Flight attendants (FAs) may be at risk of adverse reproductive outcomes. We investigated the feasibility of biomonitoring studies in this mobile workforce. Forty-five female FAs and 26 female teachers (referents) collected daily urine and saliva samples for one menstrual cycle, provided daily diary data for approximately three months, and wore a wrist monitor to measure sleep disruption. A transport system enabled FAs to store samples while traveling. Overall, participation rates were low (37%) but of those recruited, over 90% of FAs and teachers completed the biomonitoring cycle. Data collection and sample integrity were not diminished by travel. Study methods resulted in good compliance and high quality data. It is possible to conduct studies of menstrual cycle function, sleep disruption, and circadian rhythm disruption in a mobile workforce potentially exposed to reproductive hazards.

Urinary reproductive hormone level differences between African American and Caucasian women of reproductive age

OBJECTIVE

To compare urinary levels of reproductive hormones in African American and Caucasian women.

DESIGN

Cross-sectional study.

SETTING

Ten United States Air Force (USAF) bases.

PATIENT(S)

African American (n = 33) and Caucasian (n = 65) women of reproductive age from a larger study of USAF women (n = 170).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Urinary endocrine end points: follicular luteinizing hormone (LH), preovulatory LH, level of LH surge peak, early follicular follicle stimulating hormone (FSH), follicular LH:FSH ratio, midluteal FSH, FSH rise before menses, early follicular estrone 3-glucuronide (E(1)3G), midfollicular E(1)3G, periovulatory E(1)3G peak, midluteal E(1)3G, early follicular pregnanediol 3-glucuronide (Pd3G), follicular Pd3G, rate of periovulatory Pd3G increase, E(1)3G:Pd3G on the day of luteal transition, slope of E(1)3G:Pd3G, and midluteal Pd3G.

RESULT(S)

Relative to Caucasians, African American women had significantly lower follicular phase LH:FSH ratios (mean +/- SD: 0.7 +/- 0.4 vs. 1.0 +/- 0.6), lower follicular phase Pd3G levels (1.0 +/- 0.5 vs. 1.2 +/- 0.8 microg/mg creatinine), and lower rates of periovulatory Pd3G increase (0.5 +/- 0.7 vs. 1.0 +/- 1.2 microg/mg creatinine).

CONCLUSION(S)

Findings of this analysis should be considered preliminary evidence of racial differences in hormone levels. Future studies are needed to determine whether these differences have clinical significance.

An algorithm for detecting features of the hormone profiles of the human menstrual cycle

An algorithm for detecting features of the cycles of the gonadotropic and ovarian hormones in women is described. The algorithm can detect hormone peaks and normal cycles defined in terms of the peaks in sequences of measurements that have an arbitrary starting point in the menstrual cycle and are of arbitrary length. The algorithm makes use of fuzzy set theory and is optimized using signal detection theory.

Preimplantation urinary hormone profiles and the probability of conception in healthy women

OBJECTIVE

To examine hormonal predictors of conception in menstrual cycles from normal women.

DESIGN

Longitudinal study.

SETTING

Community.

PATIENT(S)

Two hundred fifteen healthy female volunteers with no known fertility problems who were trying to conceive.

INTERVENTION(S)

Participants recorded menstrual bleeding, sexual intercourse, and collected first morning urine specimens daily from when they stopped contraception until they became pregnant or for 6 months if no clinical pregnancy was achieved. Measurements were made of urinary LH and urinary metabolites of estrogen and progesterone.

MAIN OUTCOME MEASURE(S)

Conception was identified by a sensitive and specific immunoradiometric assay for urinary hCG.

RESULT(S)

Statistical analyses of 189 conception and 409 nonconception cycles controlled for sexual intercourse and interdependence of cycles from the same woman. Conception was more likely in cycles with lower baseline progesterone metabolite levels, higher ovulatory LH, and higher midluteal progesterone. Midluteal estrogen also was elevated in conception cycles when examined without adjusting for other hormone levels, but this finding did not persist after multivariate adjustment.

CONCLUSIONS

Menstrual cycles in normal women vary in their hormonal quality in ways that are predictive of cycle fertility.

Stability of urinary female reproductive hormones stored under various conditions

Urinary reproductive hormones afford specific and sensitive evaluation of female reproductive potential in epidemiologic and clinical settings. The goal of this study was to characterize the stability of urinary luteinizing hormone, follicle stimulating hormone, estrone 3-glucuronide, pregnanediol 3-glucuronide, and creatinine during storage as functions of time, temperature, and additives. After 2 weeks with no additives, activity of the four analytes, relative to initial concentrations, ranged from 91.9 to 102.8% at 4 degrees C, 35.1 to 89.6% at 25 degrees C, and 7.5 to 66.9% at 37 degrees C. Antimicrobial additives did not consistently improve stability. Analyte activity for samples stored with no additives for 24 weeks at -80 degrees C ranged from 69.0 to 101.2%. Glycerol and bovine serum albumin improved analyte stability; activity ranged from 91.1 to 106.3%. Other additives were ineffective. These results reveal conditions for storing reproductive hormone analytes in urine during epidemiologic field studies.

Validations of time-resolved fluoroimmunoassays for urinary estrone 3-glucuronide and pregnanediol 3-glucuronide

Competitive time-resolved fluoroimmunoassays (FIAs) were developed for measuring 1,3,5(10)-estratrien-3-ol-17-one glucosiduronate (estrone 3-glucuronide, E(1)3G) and 5 beta-Pregnane-3 alpha,20 alpha-diol 3-glucosiduronate (pregnanediol 3-glucuronide, Pd3G) in unextracted urine. The assays are specific, detect 0.98 ng E(1)3G/mL and 0.035 microgram Pd3G/mL, measure 102.8 +/- 2.0% of E(1)3G and 93.6 +/- 2.9% of Pd3G added, and exhibit between and within assay coefficients of variation, respectively, of 5.3% and 7.1% for E(1)3G and 6.8% and 7.8% for Pd3G. The urine matrix does not interfere with the assay. Urinary steroid glucuronide profiles measured by these FIAs conform to those of urinary steroid glucuronides and serum estradiol and progesterone measured by other established immunoassays. These FIAs afford the advantages of non-radioisotopic procedures and urine sample collection (convenience, non-invasiveness, integration of pulsatile secretion) to evaluate menstrual function in epidemiological, medical, and athletic populations.