Search PubMed⌕ Search

Biomedical subjects

Peter T Ellison

Publications and source records attributed to Peter T Ellison.

14 recordsLinked to original sources
PubMed2005

Metabolic and hormonal profiles: HDL cholesterol as a plausible biomarker of breast cancer risk. The Norwegian EBBA Study.

Low serum high-density lipoprotein cholesterol (HDL-C) is an important component of the metabolic syndrome and has recently been related to increased breast cancer risk in overweight and obese women. We therefore questioned whether serum HDL-C might be a biologically sound marker of breast cancer risk. We obtained cross-sectional data among 206 healthy women ages 25 to 35 years who participated in the Norwegian EBBA study. We included salivary ovarian steroid concentrations assessed by daily samples throughout one entire menstrual cycle, metabolic profile with measures of adiposity [body mass index (BMI) and truncal fat percentage], serum concentrations of lipids and hormones (insulin, leptin, testosterone, dehydroepiandrostendione sulfate, insulin-like growth factor-I, and its principal binding protein), and mammographic parenchymal pattern. We examined how components of the metabolic syndrome, including low serum HDL-C, were related to levels of hormones, and free estradiol concentration in particular, and studied predictors of mammographic parenchymal patterns in regression models. In women with BMI > or = 23.6 kg/m(2) (median), overall average salivary estradiol concentration dropped by 2.4 pmol/L (0.7 pg/mL; 13.2% change in mean for the total population) by each 0.33 mmol/L (12.8 mg/dl; 1SD) increase in serum HDL-C (P = 0.03; P(interaction) = 0.03). A subgroup of women characterized by both relatively high BMI (> or =23.6 kg/m(2)) and high serum LDL-C/HDL-C ratio (> or = 2.08; 75 percentile) had substantially higher levels of salivary estradiol by cycle day than other women (P = 0.001). BMI was the strongest predictor of overall average estradiol with a direct relationship (P< 0.001). Serum HDL-C was inversely related to serum leptin, insulin, and dehydroepiandrostendione sulfate (P < 0.001, P < 0.01, and P < 0.05, respectively). There was a direct relationship between breast density and healthy metabolic profiles (low BMI, high serum HDL-C; P < 0.001) and salivary progesterone concentrations (P < 0.05). Our findings support the hypothesis that low serum HDL-C might reflect an unfavorable hormonal profile with, in particular, increased levels of estrogens and gives further clues to biomarkers of breast cancer risk especially in overweight and obese women.

Adult↗
PubMed2004

Large breasts and narrow waists indicate high reproductive potential in women.

Physical characteristics, such as breast size and waist-to-hip ratio (WHR), function as important features used by human males to assess female attractiveness. Males supposedly pay attention to these features because they serve as cues to fecundity and health. Here, we document that women with higher breast-to-underbreast ratio (large breasts) and women with relatively low WHR (narrow waists) have higher fecundity as assessed by precise measurements of daily levels of 17-beta-oestradiol (E2) and progesterone. Furthermore, women who are characterized by both narrow waists and large breasts have 26% higher mean E2 and 37% higher mean mid-cycle E2 levels than women from three groups with other combinations of body-shape variables, i.e. low WHR with small breasts and high WHR with either large or small breasts. Such gains in hormone levels among the preferred mates may lead to a substantial rise in the probability of conception, thus providing a significant fitness benefit.

Adult↗
PubMed2004

The relationship of male testosterone to components of mental rotation.

Studies suggest that higher levels of testosterone (T) in males contribute to their advantage over females in tests of spatial ability. However, the mechanisms that underlie the effects of T on spatial ability are not understood. We investigated the relationship of salivary T in men to performance on a computerized version of the mental rotation task (MRT) developed by [Science 171 (3972) (1971) 701]. We studied whether T is associated specifically with the ability to mentally rotate objects or with other aspects of the task. We collected hormonal and cognitive data from 27 college-age men on 2 days of testing. Subjects evaluated whether two block objects presented at different orientations were the same or different. We recorded each subject's mean response time (RT) and error rate (ER) and computed the slopes and intercepts of the functions relating performance to angular disparity. T level was negatively correlated with ER and RT; these effects arose from correlations with the intercepts but not the slopes of the rotation functions. These results suggest that T may facilitate male performance on MRTs by affecting cognitive processes unrelated to changing the orientation of imagined objects; including encoding stimuli, initiating the transformation processes, making a comparison and decision, or producing a response.

Adult↗
PubMed2004

Social variables predict between-subject but not day-to-day variation in the testosterone of US men.

Previous research has shown lower testosterone (T) levels associated with involvement in committed, romantic relationships ("paired" men) and paternal care in eight studies of North American men. An unanswered question is whether differences in male T levels associated with relationship status better reflect state (e.g., a man has lower T levels because he is involved in a relationship) or trait (e.g., low T men are more inclined toward such relationships) effects. Toward addressing this question, this paper presents data on male salivary T levels among a sample of 65 men varying in marital and parental status. Subjects collected saliva samples (at approximately waking, 17:00 and 21:00 h) and filled out questionnaires concerning their activities on four days. Each subject collected samples in two settings that varied in social interactions: for unmarried men, two working and two non-working days; for married non-fathers, two days spent mostly with their wives and two days spent mostly away from their wives; and for married fathers, two days spent mostly with their young children and two days spent mostly away from their children. Analyses revealed no significant within-subject T differences between these different conditions. However, between-group analyses revealed that married men had lower evening T levels than unmarried men, corroborating existing North American studies of male T and relationship status. These results suggest that day-to-day differences in social interactions may not be associated with differences in T levels, and lend further support to the growing body of evidence that hormone-behavior effect sizes may be greater in the afternoon and evening than in the morning.

Adult↗
PubMed2004

Lactational amenorrhoea in well-nourished Toba women of Formosa, Argentina.

The proximate causes of the contraceptive effect of lactation are still a matter of productive debate. This study sought to disentangle the relative impact that intense breast-feeding practices and maternal nutrition have on the regulation of ovarian function in nursing women. A mixed-longitudinal, direct-observational, prospective study was conducted of the return to postpartum fecundity in 113 breast-feeding, well-nourished Toba women. A sub-sample of 70 women provided data on nursing behaviour, daily activities, diet quality and urinary levels of oestrone and progesterone metabolites. Well-nourished, intensively breast-feeding Toba women experienced a relatively short period of lactational amenorrhoea (10.2 +/- 4.3 months) and a high lifetime fertility (TFR=6.7 live births/woman). Duration of lactational amenorrhoea was not correlated with any of the nursing parameters under study or with static measures of maternal nutritional status. The results indicated that the pattern of resumption of postpartum fertility could be explained, at least partly, by differences in individual metabolic budgets. Toba women resumed postpartum ovulation after a period of sustained positive energy balance. As the relative metabolic load hypothesis suggests, the variable effect of lactation on postpartum fertility may not depend on the intensity of nursing per se but rather on the energetic stress that lactation represents for the individual mother.

Adolescent↗
PubMed2002

Population variation in age-related decline in male salivary testosterone.

BACKGROUND: Age-related declines in free and bioavailable testosterone are frequently reported for Western populations, but interpopulation variation in this pattern has not previously been investigated. METHODS: Salivary testosterone was measured using a consistently applied protocol on morning samples collected from men in four populations (USA, Congo, Nepal, and Paraguay) representing different geographical, ecological, and cultural settings. RESULTS: Mean testosterone levels varied significantly between the four populations. The mean testosterone differences between populations were greatest for young men (aged 15-30 years) and insignificant for older men (aged 45-60 years). The slope of age-related decline in testosterone was significant in the USA and Congolese participants, but not in the Nepalese or Paraguayan participants. CONCLUSIONS: Age patterns of testosterone decline vary between populations primarily as a result of variation in the peak levels attained in young adulthood. The potential consequences of this variation for other aspects of male health deserve investigation.

Adolescent↗
PubMedDate not supplied

Energetics and reproductive effort.

Natural selection favors the optimal allocation of energy and other limiting resources to reproduction. Human reproductive physiology displays characteristic patterns that can be viewed as mechanisms that help optimize reproductive effort in the face of environmental energetic constraints. Female ovarian function is particularly sensitive to energy balance and energy flux, resulting in a synchronization of conception with favorable energetic conditions. Reproductive effort during gestation is highly buffered from environmental energetic constraints, but the duration of gestation and final birthweight are both very sensitive to maternal energy availability. Milk production during lactation is relatively buffered from maternal energetic constraints as well, but the duration of lactational amenorrhea is sensitive to the relative metabolic load of lactation. Male gamete production is very insensitive to energetic constraints, but variation in testosterone production in response to both age and longer-lasting energetic conditions contributes to the modulation of somatic and behavioral aspects of male reproductive effort, aspects that are more energetically costly for a male. There is also new evidence that testosterone may also help to modulate the trade-off between male parenting and mating effort.

Amenorrhea↗
PubMedDate not supplied

Effects of developmental and adult androgens on male abdominal adiposity.

We present results from 42 gay men who completed a survey including self-measurement of waist circumference, height, and weight, in addition to providing saliva samples for the assay of testosterone, and a photocopy of the right hand for the measure of second-to-fourth digit length ratio (2D:4D), proposed as a means of approximating androgenic effects during development. The analyses were conducted as a test of the recent hypothesis, proposed by Abbott et al. ([2002] J Endocrinol 174:1-5), that high prenatal androgen exposure causes greater deposition of fat on the abdomen relative to other depots. We found support for this hypothesis in men, albeit in a limited sample and with self-reported and self-collected data.

Abdomen↗
PubMedDate not supplied

Impact of breastfeeding on anthropometric changes in peri-urban Toba women (Argentina).

We present an analysis of the effect of lactation on average maternal anthropometric and body composition measures in a population of Toba women in Formosa, Argentina. This indigenous population is undergoing a continuing transition from a seminomadic hunter-gatherer lifestyle to a sedentary, peri-urban one. Using a mixed-longitudinal design, we measured monthly maternal body mass index (BMI), body fat percentage, and triceps and subscapular skinfold thickness between birth and the 18th month postpartum in 113 breastfeeding women. The pattern of change in postpartum body composition varied with maternal age. Adult women (20 years old and older) did not show significant changes in any of the anthropometric measures during the entire study. Older adult women (30 years old and older) consistently had the highest values in measures of BMI and percentage fat, and tended to retain weight postpartum. Adolescent subjects (19 years old and younger) tended to lose weight during the first 6 months postpartum but regain their prepregnancy weight by 12 months postpartum. The same patterns were observed for changes in body fat percentage and in skinfold thickness. We conclude that in this population the energetic stress of lactation does not pose a serious challenge to the maintenance of long-term maternal energy balance or to short-term energy balance in women over 20 years of age. From a public health perspective, postpartum weight retention in older women may represent a more serious health threat. The low level of energetic stress associated with lactation may also contribute to the relatively short duration of lactational amenorrhea in this population despite a cultural pattern of intensive breastfeeding. Am. J. Hum. Biol. 15:717-724, 2003.

Adult↗
PubMedDate not supplied

Retracted article.

Explore the source record for details and available documents.

Retraction Notice↗
PubMedDate not supplied

Energetic factors and seasonal changes in ovarian function in women from rural Poland.

Female mammals can optimize their fitness by temporal suppression of reproductive function in response to unfavorable environmental conditions. Since reproduction is energetically demanding for a human female, ovarian function is expected to be sensitive to factors influencing energy availability and metabolism. Dieting and exercise in women from industrial countries, and low-calorie diet and workload in women from developing countries, are often associated with ovarian suppression. This study shows that in Polish rural women seasonal changes in workload correlate with seasonal changes in indices of ovarian function (progesterone measured in saliva samples collected daily for six menstrual cycles for each subject). Mean levels of energy expenditure of the most work demanding weeks of the summer exceeded mean levels of energy expenditure during winter by 37%. Energy intake in this population was sufficient throughout the year. During the summer, when physical work was most intense, low values of progesterone levels were observed (178.2 pmol/L in July and 182.2 pmol/L in August), indicating ovarian suppression. Mean progesterone levels rose to 234.6 pmol/L in October when levels of energy expenditure were lower due to cessation of harvest-related activities. As indicated by several causal models tested through path analysis, energy expenditure was the only variable responsible for suppressed progesterone levels during the summer. Variables describing the nutritional status and energy balance did not correlate significantly with progesterone levels; neither body weight nor body fat or seasonal changes of these variables seem to influence ovarian function in this population. Thus work-related energy expenditure does not need to lead to negative energy balance in order to cause suppression of reproductive function in women.

Adult↗
PubMedDate not supplied

Testosterone, aging, and body composition in men from Harare, Zimbabwe.

To examine age-related changes in body composition and testosterone (T) among men in an urban sub-Saharan African population, measures of body composition and salivary T were obtained from 109 males ages 20-78 in Harare, Zimbabwe. Measures included height, weight, suprailiac and triceps skinfold, and percent body fat by bioelectric impedance (BIA). Saliva samples were assayed for T using radioimmunoassay. Average BMI of the overall sample (23.16 (SD = 18.12) kg/m(2) was close to Western populations, while salivary T levels (AM = 196 +/- 96 pmol/l; pm = 172 +/- 98 pmol/l) were much lower. Both morning (beta = -0.535; P < 0.001) and afternoon salivary T declined with age (beta = -0.385; P < 0.001). Multiple regression models indicate that pm salivary T (beta = 0.24; P = 0.025), was a predictor of fat-free mass, but neither am nor pm salivary T was related to fat mass or other measures of body composition. In addition, height was significantly related to pm salivary T levels in men under the age of 60. Multivariate regression indicates that pm salivary T is a predictor of fat-free mass when controlled for height and adiposity. These findings suggest that T is related to both lean mass and overall body size among men from a non-Western nonsubsistence population. As such they are consistent with the hypothesis that bioavailable T plays a role in energetic allocation among human males.

Adult↗
PubMedDate not supplied

Evolutionary perspectives on the fetal origins hypothesis.

The fetal origins hypothesis, or Barker hypothesis, is both stimulating and challenging for evolutionary human biologists. While evidence of a correlation between conditions around the time of birth and later health outcomes has been presented before, the more recent evidence of a connection between fetal growth and chronic disease risk later in life has attracted considerable attention among epidemiologists and human biologists. Several themes that are fundamental to human biology emerge from an engagement with the fetal origins hypothesis. Among them are the tension between concepts of pathology, constraint, and adaptation; the importance of a life history perspective that embraces the notion of trade-offs; the question of environmental predictability; and the mechanisms of energy mobilization and allocation. Bringing the insights of evolutionary biology to bear on the fetal origins hypothesis illustrates the value of the field now known as evolutionary medicine.

Adaptation, Physiological↗