Production of human chorionic gonadotropin during the normal menstrual cycle

OBJECTIVE

To present a comprehensive study of pituitary human chorionic gonadotropin (hCG) production during the menstrual cycle, investigating its occurrence, timing and the possibility of a separate biologic role for pituitary hCG during the normal menstrual cycle.

STUDY DESIGN

Daily urine samples were tested from 185 women during 405 normal menstrual cycles. Levels of hCG and luteinizing hormone (LH) were measured daily.

RESULTS

hCG levels were detected at LH peak in 84% of menstrual cycles. At this time, hCG levels paralleled LH values. The remaining menstrual cycles (16%) had significantly lower LH levels, suggesting lack of detection of hCG as a result of low concentration of LH or very dilute urines. We infer that hCG is produced in all menstrual cycles.

CONCLUSION

hCG is seemingly produced alongside LH in all menstrual cycles. hCG has a much greater circulating half-life compared to LH. It may function to extend the short, sharp LH peak in promoting ovulation or in promoting initial progesterone production by the corpus luteal cells.

Timing clinic visits to phases of the menstrual cycle by using a fertility monitor: the BioCycle Study

Planning study visits during specific menstrual cycle phases is important if the exposure or outcome is influenced by hormonal variation. However, hormone profiles differ across cycles and across women. The value of using fertility monitors to time clinic visits was evaluated in the BioCycle Study (2005-2007). Women aged 18-44 years (mean, 27.4) with self-reported menstrual cycle lengths of 21-35 days were recruited in Buffalo, New York, for 2 cycles (n = 250). Participants were provided with home fertility monitors that measured urinary estrone-3-glucuronide and luteinizing hormone (LH). The women were instructed to visit the clinic for a blood draw when the monitor indicated an LH surge. The monitor recorded a surge during 76% of the first cycles and 78% of the second cycles. Scheduling visits by using set cycle days or algorithms based on cycle length, such as a midcycle window or a window determined by assuming a fixed luteal phase length, would be simpler. However, even with perfect attendance in a 3-day window, these methods would have performed poorly, capturing the monitor-detected LH surge only 37%-57% of the time. Fertility monitors appear to be useful in timing clinic visits in a compliant population with flexible schedules.

Cerebral white matter in early puberty is associated with luteinizing hormone concentrations

Puberty is a period in which cerebral white matter grows considerably, whereas gray matter decreases. The first endocrinological marker of puberty in both boys and girls is an increased secretion of luteinizing hormone (LH). Here we investigated the phenotypic association between LH, global and focal gray and white matter in 104 healthy nine-year-old monozygotic and dizygotic twins. Volumetric MRI and voxel-based morphometry were applied to measure global gray and white matter and to estimate relative concentrations of regional cerebral gray and white matter, respectively. A possible common genetic origin of this association (genetic correlation) was examined. Results showed that higher LH levels are associated with a larger global white matter proportion and with higher regional white matter density. Areas of increased white matter density included the cingulum, middle temporal gyrus and splenium of the corpus callosum. No association between LH and global gray matter proportion or regional gray matter density was found. Our data indicate that a common genetic factor underlies the association between LH level and regional white matter density. We suggest that the increase of white matter growth during puberty reported earlier might be directly or indirectly mediated by LH production. In addition, genes involved in LH production may be promising candidate genes in neuropsychiatric illnesses with an onset in early adolescence.

Onset of ovulation after menarche in girls: a longitudinal study

INTRODUCTION

Hypothalamic-pituitary axis maturity has been believed to be the rate-limiting step in the development of ovulatory menstrual cycles. We hypothesized that, given current nutritional conditions, hypothalamic-pituitary axis maturation would be relatively rapid in menarcheal girls.

METHODS

Daily urine and menstrual records were collected for 2 yr each from 10 girls aged 11-13 yr at study entry. Urinary excretion of LH, FSH, estradiol (E1c), and progesterone (Pdg) metabolites was measured using established ELISAs. An objective algorithm detected rises of LH, FSH, E1c, and Pdg consistent with follicular maturation and/or ovulation.

RESULTS

Nine of 10 girls enrolled into the study experienced the onset of menarche prior to or during the 2-yr collection period. LH and FSH surges, as well as small amplitude Pdg increments, were observed prior to menarche. Regular, ovulatory-appearing cycles with LH surges and gradually increasing and more sustained Pdg rises were observed over time after menarche, although duration of Pdg elevations remained shorter than in adult women (8.9 +/- 1.0 vs. 12.1 +/- 0.8 d, P = 0.043). E1c levels leading to LH/FSH surges were lower in perimenarcheal girls than adult controls, and bleeding episodes did not uniformly correlate with hormone patterns. Progressive increases in FSH and Pdg, but not LH or E1c, were observed in association with menarche.

CONCLUSION

Mature hormone patterns are established within several months of and even prior to menarche in normal-weight perimenarcheal girls. Factors determining menstrual bleeding in perimenarcheal girls may not be solely dependent on reproductive hormones or the neuroendocrine axis.

Pulsatile luteinizing hormone amplitude and progesterone metabolite excretion are reduced in obese women

CONTEXT

Female obesity is linked to abnormal menstrual cycles, infertility, reproductive wastage, and deficient LH, FSH, and progesterone secretion.

OBJECTIVE AND DESIGN

To elucidate the reproductive defects associated with obesity, we sampled 18 eumenorrheic (nonpolycystic ovary syndrome) women with a mean +/- sem body mass index of 48.6 +/- 1.4 kg/m2 with daily, first morning voided urine collections, seven of whom also had early follicular phase 12-h, every 10-min blood sampling to assess LH pulses. Daily hormones were compared with 11 eumenorrheic, normal-weight controls. A separate control group of 12 eumenorrheic, normal-weight women was used for the LH pulse studies.

MAIN OUTCOME MEASURES

Assays for LH (serum and urine) and FSH, and estradiol and progesterone metabolites (estrone conjugate and pregnanediol glucuronide; urine) were performed. Daily hormones were meaned and normalized to a 28-d cycle length. LH pulsations were determined using two objective methods. Group means were compared using t tests.

RESULTS

Reduced whole-cycle mean, normalized pregnanediol glucuronide was observed in obese (38.2 +/- 2.1 microg/mg creatine) compared with normal-weight women (181.3 +/- 35.1 microg/mg creatine; P = 0.002), without significant differences in LH, FSH, or estrone conjugate. Early follicular phase LH pulse frequency did not differ from normal-weight women, but both amplitude and mean LH were dramatically reduced in obese women (0.8 +/- 0.1 and 2.0 +/- 0.3 IU/liter) compared with controls (1.6 +/- 0.2 and 3.4 +/- 0.2 IU/liter; P < 0.01).

CONCLUSIONS

A novel defect in the amplitude but not the frequency of LH pulsations appears to underlie the reproductive phenotype of obesity. The deficit in pregnanediol glucuronide appears to exceed the deficit in LH. The patterns of hypothalamic-pituitary-ovarian axis function unique to the obese state differ from other abnormal reproductive states.

Long-term estrogen deficiency lowers regional blood flow, resting systolic blood pressure, and heart rate in exercising premenopausal women

The cardiovascular consequences of hypoestrogenism in premenopausal women are unclear. Accordingly, the influence of menstrual status and endogenous estrogen (E(2)) exposure on blood pressure (BP), heart rate (HR), and calf blood flow in young (18-35 yr) regularly exercising premenopausal women with exercise-associated menstrual aberrations was investigated. Across consecutive menstrual cycles, daily urinary ovarian steroid levels were analyzed, and the area under the curve was calculated to determine menstrual status and E(2) exposure. BP, HR, blood flow, vascular conductance, and resistance were measured at baseline and following ischemic calf exercise. Exercising subjects consisted of 14 ovulatory (ExOv), 10 short-term (anovulatory and <or=100 days amenorrhea; ST-E(2) Def), and 8 long-term (>100 days amenorrhea; LT-E(2) Def) E(2)-deficient women. Nine sedentary ovulatory subjects (SedOv) were also studied. All groups were similar in age (24.8 +/- 0.7 yr), height (164.8 +/- 1.3 cm), weight (57.9 +/- 0.9 kg), and body mass index (21.3 +/- 0.3 kg/m(2)). E(2)-deficient groups had lower (P < 0.002) E(2) exposure compared with ovulatory groups. Resting systolic BP, HR, blood flow, and vascular conductance were lower (P < 0.05) and vascular resistance higher (P < 0.05) in LT-E(2) Def compared with both ovulatory groups. Peak ischemic blood flow, vascular conductance, and HR were also lower (P < 0.05) and vascular resistance higher (P < 0.05) in LT-E(2) Def compared with all other groups. Our findings show that exercising women with long-term E(2) deficiency have impaired regional blood flow and lower systolic BP and HR compared with exercising and sedentary ovulatory women. These cardiovascular alterations represent markers of altered vascular function and autonomic regulation of which the long-term effects remain unknown.

Monitoring reproductive aging in a 5-year prospective study: aggregate and individual changes in luteinizing hormone and follicle-stimulating hormone with age

OBJECTIVE

This study describes age-related changes in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in a 5-year prospective study of reproductive aging.

DESIGN

Participants (n = 156 college-educated, white, US women; 25 to 58 y) were recruited from the TREMIN Research Program on Women's Health. They collected daily urine specimens for 6 months in each of 5 consecutive years. Specimens were assayed for LH and FSH. Aggregate changes were calculated in LH and FSH with age, and multilevel models were used to estimate individual hormone trajectories and within-woman and between-woman variances by age.

RESULTS

Aggregate LH levels increased beginning after age 45; FSH increased at all ages, accelerating after age 45. Individual-level patterns with age included the following: reproductive-age LH and FSH levels, with increasing FSH and increasing or decreasing LH (ages 20 to 49); rapidly increasing LH and FSH (ages 40 to 59); and increasing or steady postmenopausal LH and FSH (ages 46 to 62). FSH levels were consistently high in the latter category, but LH levels overlapped with levels found in younger women (<45 y). Individual LH patterns showed more variability (5% to 35% of total variance) than FSH (3% to 22% of total variance). Both hormones had relatively low variation within individuals compared with between-woman differences (65% to 97% of total variance).

CONCLUSIONS

Aggregate-level data do not reflect differences across women and oversimplify the age-related increases and variability in LH and FSH. Individual FSH levels are not distinguishable from reproductive-age levels until after rapid perimenopausal increases in FSH occur; individuals vary in whether their postmenopausal LH levels are distinguishable from reproductive-age levels.

Characteristics of the urinary luteinizing hormone surge in young ovulatory women

OBJECTIVE

To define characteristics of the luteinizing hormone (LH) surge in urine.

DESIGN

Observational study.

SETTING

Academic center.

PATIENT(S)

46 women aged 20 to 35 years with regular menstrual cycles.

INTERVENTION(S)

Collected first morning urine daily, throughout one menstrual cycle.

MAIN OUTCOME MEASURE(S)

Urinary LH, follicle-stimulating hormone (FSH), estrone conjugate (E1C), and pregnanediol-3-glucuronide (PDG).

RESULT(S)

Three women lacked LH surges. Mean LH surge: start = day 14.5 (+/-3.6 SD) (range: 9-26); peak = 41.2 mIU/mg creatinine (+/-20 SD) (range: 12.1-104.0); fold increase = 7.7 (+/-3.0 SD) (range: 2.5-14.8); duration = 7.6 days (+/-1.5 SD) (range: 5-11). The onset of LH surge was of two types: rapid onset (within 1 day) (42.9%) or gradual onset (2 to 6 days) (57.1%). Configurations of LH surges were of three types: spike (41.9%), biphasic (44.2%), or plateau (13.9%). All LH surges demonstrated a gradual decrease to baseline. Three women (7%) did not have FSH rises coincident with LH surges. All displayed E1C rises during the middle to late follicular phase.

CONCLUSION(S)

The LH surges that result in ovulation are extremely variable in configuration, amplitude, and duration. The FSH rise does not seem essential for ovulation. However, an E1C rise occurred in all cycles, confirming the critical role of estrogen in induction of the LH surge.

Characterizing daily urinary hormone profiles for women at midlife using functional data analysis

The availability of daily hormone values for entire menstrual cycles offers an opportunity to apply new analytic techniques that confirm current knowledge and provide new insights into patterns of changing hormone profiles in women as they transition to the menopause. The Study of Women's Health Across the Nation (SWAN) collected urine samples during 1997-1999 from one menstrual cycle or up to 50 days from 848 women who live in seven cities across the United States. These samples were assayed for the urinary forms of estrogen, progesterone, follicle-stimulating hormone, and luteinizing hormone. The authors used functional data analysis to study variability in the hormone patterns of 572 of the 848 pre- and early-perimenopausal women with evidence of a luteal transition. Functional data analysis enabled the authors to identify asymmetries in women's hormone patterns related to cycle length that are not captured with single hormone value comparisons. Longer cycles were characterized by increasing dyssynchrony between follicle-stimulating hormone and luteinizing hormone in the luteal phase.

Pituitary-gonadal function in adolescent males born appropriate or small for gestational age with or without intrauterine growth restriction

CONTEXT

Being born small for gestational age (SGA) is suggested to influence female pituitary-gonadal axis, but only a few studies have focused on male pituitary-gonadal function.

OBJECTIVE

Our objective was to evaluate the influence of fetal growth rate on male reproductive function.

DESIGN

We conducted a follow-up study of a prospective study with data on third trimester fetal growth velocity and birth weight.

SETTING

The study was conducted at Copenhagen University Hospital.

PARTICIPANTS

Fifty-two healthy adolescent males participated. They were divided into those born appropriate for gestational age (AGA) and SGA, with or without intrauterine growth restriction.

MAIN OUTCOME MEASURES

Pubertal stage, testicular size, and reproductive hormones were determined. Overnight 20-min LH and FSH profiles and overnight urine LH and FSH were determined in an additional study (n=30).

RESULTS

No significant differences were found in testosterone levels (19.2 vs. 18.9 nmol/liter), inhibin B levels (186.5 vs. 188.0 pg/ml), or LH/testosterone ratio (0.15 vs. 0.18) between AGA and SGA, respectively. No significant differences in overnight secretory patterns of gonadotropins or testicular size and morphology were determined by ultrasonography between AGA and SGA. Fetal growth velocity did not influence any of the reproductive hormone levels. Overnight urinary LH and FSH excretion correlated statistically significantly with overnight LH (r=0.50; P=0.02) and FSH (r=0.44; P=0.04) secretion, respectively.

CONCLUSION

Poor third trimester growth and/or low birth weight had no effect on subsequent male reproductive hormones. Contrasting a previous study, we found no difference in testosterone or inhibin B levels between SGA and AGA, suggesting that testicular function was not impaired in adolescent males born after compromised fetal growth.

Mistiming of intercourse as a primary cause of failure to conceive: results of a survey on use of a home-use fertility monitor

OBJECTIVE

To assess demographics, fecundity characteristics and fertility history of couples who successfully conceived using a home-use Fertility Monitor.

STUDY DESIGN

This was a retrospective US observational study of couples who successfully conceived using a Fertility Monitor. Data were self-reported by volunteers using a questionnaire supplied and collected by mail. Of 276 surveys distributed, 196 (71.0%) were returned and evaluated.

RESULTS

Length of time trying to conceive was < 12 months for 70% of women; proportions were similar across age groupings. After switching to the Fertility Monitor, 49.5% and 91.9% of women had conceived within first and third cycles, respectively. Prior to Fertility Monitor use, conception aids were used by 84.2% and 64.3% had consulted a physician to seek help in attempting to conceive. Average costs of prior treatment were (in US dollars) 6637 dollars; median costs for infertility evaluation were 1075 dollars per cycle. Fertility Monitor costs ranged from 250 dollars for one cycle to 550 dollars after 10 cycles.

CONCLUSIONS

A probable cause for failure to conceive appeared to be mistiming of intercourse. The issue of early intervention with tests and medications were highlighted, resulting in escalating costs and strain on the couple. The use of a home Fertility Monitor that identifies all fertile days of the cycle and allows couples to target intercourse accordingly, should be considered as an alternative choice for couples seeking to conceive during the first year, before other attempts at infertility diagnosis are made, unless there are conflicting clinical reasons.

Performance characteristics of two immunoassays for the measurement of urinary luteinizing hormone

Urine luteinizing hormone (LH) concentration is routinely measured in all anti-doping laboratories to exclude recombinant LH abuse and to test any potential alteration of the hypophyseal-gonadal axis. Before establishing proper reference values among professional top level athletes, an extended validation of two commercial immunoassays for LH measurements was performed. Elecsys 1010 and Access are two automated immunoanalyzers for central laboratories. The limit of detection, the limit of quantification, intra-laboratory, inter-technique correlation, precision, accuracy were determined. Furthermore, reference urinary LH distribution values for male and female top level athletes were determined. Stability studies of LH in urine following freezing and thawing cycles (n=3) as well as storage conditions at room temperature, 4 degrees C and -20 degrees C were performed. Male and female subjects showed important urinary corrected (specific gravity correction) LH distribution differences. Intra-assay precision for the Access analyzer was less than 8.0% whereas inter-assay was close to 11%. Intra and inter-assay precision for the Elecsys 1010 analyzer was slightly better. A good inter-technique correlation was obtained ([Elecsys 1010]=1.0434[Access]+1.146, R=0.953). No urinary LH loss was observed after two freezing and thawing cycles. On the other hand, time and bad storage conditions such as elevated temperature can deteriorate rapidly urinary LH. In conclusion, both analyzers showed acceptable performances and are suitable for screening anti-doping analyses. Each anti-doping laboratory has to settle its own reference distribution values and then determine when to launch a confirmation procedure. This takes place then depending on the positivity criteria the anti-doping laboratory has established and validated. This study also clearly showed that the time delay between the urine collection and the analysis should be reduced as much as possible and urine samples should be transported in optimal conditions (low temperature and quickly) to decrease urinary LH deterioration.

Ovulatory shifts in human female ornamentation: near ovulation, women dress to impress

Humans differ from many other primates in the apparent absence of obvious advertisements of fertility within the ovulatory cycle. However, recent studies demonstrate increases in women's sexual motivation near ovulation, raising the question of whether human ovulation could be marked by observable changes in overt behavior. Using a sample of 30 partnered women photographed at high and low fertility cycle phases, we show that readily-observable behaviors - self-grooming and ornamentation through attractive choice of dress - increase during the fertile phase of the ovulatory cycle. At above-chance levels, 42 judges selected photographs of women in their fertile (59.5%) rather than luteal phase (40.5%) as "trying to look more attractive." Moreover, the closer women were to ovulation when photographed in the fertile window, the more frequently their fertile photograph was chosen. Although an emerging literature indicates a variety of changes in women across the cycle, the ornamentation effect is striking in both its magnitude and its status as an overt behavioral difference that can be easily observed by others. It may help explain the previously documented finding that men's mate retention efforts increase as their partners approach ovulation.

Embryo transfer and luteal support in natural cycles

Embryo transfer policy and luteal supplementation was reviewed, comparing literature data and the results from the Maribor IVF Centre. A retrospective analysis of 1024 cycles in patients undergoing IVF, intracytoplasmic sperm injection (ICSI) or testicular sperm aspiration in unstimulated cycles was carried out using four different approaches for cycle monitoring. This showed that the most successful protocol for monitoring was administration of human chorionic gonadotrophin (HCG) when serum oestradiol was >0.49 nmol/l and follicle diameter was at least 15 mm. The implantation rate per transferred embryo was higher when a blastocyst was transferred (42.8%) rather than a day-2 embryo (23.5%) in the same monitoring protocol. Analysis of the influence of patient age on the success of oocyte retrieval, oocyte fertilization, embryo transfer rate and delivery rate demonstrates that patient age does not influence the rate of positive oocyte retrieval or fertilization rate as much as it influences pregnancy rate per embryo transfer. The delivery rate per cycle was dramatically influenced by age in patients over 38 years. There is no clear evidence in the literature as to whether luteal phase support is necessary in natural cycles for IVF/ICSI. Comparing the data, a higher pregnancy rate was observed if HCG was administered after embryo transfer.

New technologies for the study of carnivore reproduction

Routine analysis of urinary metabolites of estrogen and progesterone provided substantial information about the estrous cycle of bears. However, these data alone were not adequate to determine the precise timing of ovulation needed to maximize AI success rates, or to distinguish between pregnancy and pseudopregnancy. Therefore, there is a critical need to develop technologies that will enhance understanding of the reproductive mechanisms of ursids. Using the domestic dog as a model, three techniques were investigated for potential application to the propagation of captive endangered bears. In a modification of standard staining of bitch vaginal cells, trichrome staining of giant panda cells revealed two consistent chromic shifts 9 and 2 days prior to the periovulatory decrease in urinary estrone sulfate, enhancing the ability to predict ovarian events preceding ovulation. To further define the relationship between the decrease in estrogen and ovulation, the utility of a rapid immunochromatographic LH assay was investigated for giant pandas using a commercial LH kit canine serum. Serum collected during estrus exhibited positive test results, indicating the cross-reactivity of giant panda LH with canine LH antibodies, and preliminary data supported further development of the LH kit for the detection of LH in bear urine. Due to the limitations of hormone analysis for distinguishing pregnancy from pseudopregnancy in canids and ursids, forward-looking infrared thermography was evaluated as a method to visualize proliferating placental tissue, fetuses, or both. While further investigation is needed to confirm the utility of thermal imaging for pregnancy diagnosis in the domestic bitch, pregnancy and pseudopregnancy were successfully detected in two giant pandas.

Low bone mineral density in the early menopausal transition: role for ovulatory function

OBJECTIVE AND CONTEXT: The objective of the study was to determine whether luteal abnormalities or measures of sex steroid hormones collected across a menstrual cycle were associated with bone mineral density (BMD) at the total hip or lumbar spine.

DESIGN AND SETTING

The Study of Women's Health Across the Nation is a longitudinal, community-based study conducted at seven clinical sites. Study of Women's Health Across the Nation includes a daily hormone study substudy in which daily urine samples are collected for one menstrual cycle (up to a maximum of 50 d) each year.

PARTICIPANTS

Participants included 643 pre- and perimenopausal women, aged 43-53 yr.

MAIN OUTCOME MEASURES

BMD of the lumbar spine and total hip was measured by dual-energy x-ray densitometry. Daily urine samples were assayed for estrone conjugates, pregnanediol glucuronide, LH, and FSH, and the information from across the menstrual cycle was expressed as area under the curve (AUC). BMD levels were evaluated in relation to three menstrual cycle attributes: 1) absence or presence of ovulation; 2) luteal phase length to menstrual cycle length ratio; and 3) ovulatory disturbances, defined as anovulatory cycles or cycles with short luteal phases (<10 d).

RESULTS

Lower urine estrone conjugate AUC and higher urine FSH AUC were significantly associated with lower BMD. However, luteal abnormalities based on menstrual cycle attributes were not significantly associated with BMD at the total hip or lumbar spine after adjustment for age, body mass index, urinary hormone concentrations, menopausal status, and race/ethnicity.

CONCLUSIONS

Direct measures of urinary hormones, not menstrual cycle luteal abnormalities, were associated with lower levels of BMD.

Menstrual cycle markers of ovarian aging and sex steroid hormone genotypes

We related variation in 4 sex steroid genes to 3 phenotypic indicators of ovarian aging, including no evidence of luteal activity as a marker of anovulatory cycles, shorter or longer menstrual cycle lengths, and the profiles of metabolites of estrogens, progesterone, follicle-stimulating hormone, and luteinizing hormone measured in urine samples collected daily across a menstrual cycle in women aged 43 to 53 years. The study sample included 485 menstruating women without hormone therapy who had collected daily urine hormone samples across 1 menstrual cycle or 50 days, whichever occurred first. There were 14 single nucleotide polymorphisms from 4 genes, including estrogen receptor-alpha (ESR1), estrogen receptor-beta, aromatase, and 17beta hydroxysteroid dehydrogenase type 1, related to ovarian aging phenotypes that include the presence or absence of luteal activity, menstrual cycle lengths < or > 24 to 31 days, and profiles of urinary hormone metabolites. Women with the TT genotype of ESR1 rs3798577 have evidence of advanced ovarian aging compared with women with the CT or CC genotypes, after adjustment for race/ethnicity, chronologic age, and race/ethnicity-specific body mass index. Further, women with the TC and CC genotypes of ESR1 rs2234693 may have a greater likelihood of more advanced ovarian aging than do women with the TT genotype, adjusting for covariates. Using a candidate gene approach, 2 ESR1 polymorphisms are related to 3 phenotypic markers of ovarian aging, suggesting a possible role for the ESR1 gene in the timing of the menopausal transition.

Fitting genetic models using Markov Chain Monte Carlo algorithms with BUGS

Maximum likelihood estimation techniques are widely used in twin and family studies, but soon reach computational boundaries when applied to highly complex models (e.g., models including gene-by-environment interaction and gene-environment correlation, item response theory measurement models, repeated measures, longitudinal structures, extended pedigrees). Markov Chain Monte Carlo (MCMC) algorithms are very well suited to fit complex models with hierarchically structured data. This article introduces the key concepts of Bayesian inference and MCMC parameter estimation and provides a number of scripts describing relatively simple models to be estimated by the freely obtainable BUGS software. In addition, inference using BUGS is illustrated using a data set on follicle-stimulating hormone and luteinizing hormone levels with repeated measures. The examples provided can serve as stepping stones for more complicated models, tailored to the specific needs of the individual researcher.

The response of luteinizing hormone pulsatility to 5 days of low energy availability disappears by 14 years of gynecological age

CONTEXT

The incidence of menstrual disorders declines during adolescence. The mechanism responsible is unknown.

OBJECTIVE

The objective of the study was to test the hypothesis, formulated a priori, that the dependence of LH pulsatility and ovarian function on energy availability declines with gynecological age (years since menarche).

DESIGN

The study was a controlled experiment repeated in two menstrual cycles, performed 2001-2004.

SETTING

The study was conducted at a university laboratory and general clinical research center.

PARTICIPANTS

The study population consisted of healthy, habitually sedentary, young women of normal body composition with 5-8 yr (adolescents, n = 9) and 14-18 yr (adults, n = 10) of gynecological age recruited by advertisement from approximately 9000 women aged 18-34 yr in a college community. Samples were similar in age of menarche, length of menstrual cycle and luteal phase, body size and composition, aerobic capacity, and dietary intake. None were withdrawn due to adverse effects.

INTERVENTIONS

Interventions included energy availabilities of 45 and 10 kcal/kg of fat-free mass per day for 5 d in the early follicular phases of separate menstrual cycles in random order.

MAIN OUTCOME MEASURES

LH pulsatility, estradiol, and luteal phase length were measured.

RESULTS

Low energy availability reduced LH pulse frequency in adolescents (P < 0.01) but not adults (P = 0.39), did not increase LH pulse amplitude in either group (both P = 0.13), and suppressed 24-h mean LH in adolescents (P = 0.01) but not adults (P = 0.72). Estradiol was unaffected (both P = 0.48), but the subsequent luteal phase was shorter in adolescents (P < 0.01).

CONCLUSIONS

In women of normal body composition, the response of LH pulsatility and ovarian function to 5 d of low energy availability disappears by 14 yr of gynecological age.

Effects of 60-Hz Magnetic Field Exposure on Nocturnal 6-Sulfatoxymelatonin, Estrogens, Luteinizing Hormone, and Follicle-Stimulating Hormone in Healthy Reproductive-Age Women: Results of a Crossover Trial

PURPOSE

Exposure to residential magnetic fields may disrupt the normal nocturnal rise in melatonin levels, resulting in increased risk for breast cancer, possibly through increased levels of reproductive hormones. We investigated whether exposure to a 60-Hz magnetic field under controlled conditions is associated with a decrease in urinary nocturnal 6-sulfatoxymelatonin level and increase in luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estrogen levels in healthy premenopausal women.

METHODS

Using a crossover design, half the participants were assigned to magnetic field exposure of 5 to 10 mG greater than ambient levels for 5 consecutive nights during the early to midluteal phase of the menstrual cycle. On the last night of exposure, a nocturnal urine sample was collected. The next month, participants were sham exposed. The other half of participants were assigned the reverse order of exposure.

RESULTS

Magnetic field exposure was associated with decreased 6-sulfatoxymelatonin levels, but no changes in reproductive hormone levels were observed. Participants using prescription medications and anovulatory participants had more pronounced decreases in 6-sulfatoxymelatonin levels with magnetic field exposure.

CONCLUSION

This study provides further evidence that exposure to magnetic fields is associated with decreased nocturnal melatonin levels, but does not support the hypothesis that such exposure results in increased urinary levels of estrogens, LH, or FSH.

Relation of cardiovascular risk factors in women approaching menopause to menstrual cycle characteristics and reproductive hormones in the follicular and luteal phases

CONTEXT

Menstrual cycle characteristics may be associated with cardiovascular disease (CVD) risk.

OBJECTIVE

The objective of this study was to describe the relationships between menstrual cycle characteristics and daily reproductive hormone measures with CVD risk factors in middle-aged women.

DESIGN AND SETTING

Cross-sectional associations were examined between CVD risk factors and urinary LH, FSH, estrone conjugates, and pregnanediol glucuronide (Pdg) measured across one menstrual cycle or 50 d.

PARTICIPANTS

Menstruating women (n = 500) who were free from diabetes or past stroke or heart attack enrolled in the Daily Hormone Study-Study of Women's Health across the Nation were studied.

MAIN OUTCOME MEASURES

Body mass index (BMI), blood pressure, hemostatic, and metabolic factors were measured.

RESULTS

Few differences existed in risk factors between women with evidence of luteal activity and those with no evidence of luteal activity. Associations between elevated CVD risk factors and long cycle length were reduced substantially by age and BMI adjustments. Those with lower estrone conjugate and PdG averaged across the follicular phase had higher waist circumference, triglycerides, insulin, plasminogen activator inhibitor type-1, tissue type plasminogen activator-antigen, and factor VIIc levels in age- and BMI-adjusted analyses (P < 0.05).

CONCLUSIONS

In midlife menstruating women, a longer cycle length was related to CVD risk factors, in large part through their common association with BMI. More favorable levels of metabolic and hemostatic factors were associated with higher levels of follicular-phase estrogen, a pattern consistent with a more competent ovary, and higher levels of follicular-phase PdG, perhaps of adrenal origin. Metabolic and hemostatic factors may be sensitive to hormonal variation during the early perimenopausal transition.