Search

Testosterone has been hypothesized to modulate the trade-off between mating and parenting effort in males. Indeed, evidence from humans and other pair-bonded species suggests that fathers and men in committed relationships have lower testosterone levels than single men and men with no children. To date, only one published study has examined testosterone in relation to motherhood, finding that mothers of young children have lower testosterone than non-mothers. Here, we examine this question in 195 reproductive-age Norwegian women. Testosterone was measured in morning serum samples taken during the early follicular phase of the menstrual cycle, and marital and maternal status were assessed by questionnaire. Mothers of young children (age ≤3) had 14% lower testosterone than childless women and 19% lower testosterone than women who only had children over age 3. Among mothers, age of the youngest child strongly predicted testosterone levels. There was a trend towards lower testosterone among married women compared to unmarried women. All analyses controlled for body mass index (BMI), age, type of testosterone assay, and time of serum sample collection. This is the first study to look at testosterone concentrations in relation to marriage and motherhood in Western women, and it suggests that testosterone may differ with marital and maternal status in women, providing further corroboration of previous findings in both sexes., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The 'challenge hypothesis' posits that testosterone facilitates reproductive effort (investment in male-male competition and mate-seeking) at the expense of parenting effort (investment in offspring and mates). Multiple studies, primarily in North America, have shown that men in committed relationships, fathers, or both maintain lower levels of testosterone than unpaired men. Data from non-western populations, however, show inconsistent results. We hypothesized that much of this cross-cultural variation can be attributed to differential investment in mating versus parenting effort, even among married fathers. Here, we directly test this idea by comparing two neighbouring Tanzanian groups that exhibit divergent styles of paternal involvement: Hadza foragers and Datoga pastoralists. We predicted that high levels of paternal care by Hadza fathers would be associated with decreased testosterone in comparison with non-fathers, and that no such difference between fathers and non-fathers would be evident in Datoga men, who provide minimal direct paternal care. Twenty-seven Hadza men and 80 Datoga men between the ages of 17 and 60 provided morning and afternoon saliva samples from which testosterone was assayed. Measurements in both populations confirmed these predictions, adding further support to the hypothesis that paternal care is associated with decreased testosterone production in men.

Objective: We examined age associated variation in salivary testosterone values among Japanese males as well as anthropometric measurements., Methods: Salivary samples were collected in pretreated sodium azide treated tubes. The first series: 15-79-year-old males (n = 99); two morning and two evening samples were collected at home for two days. The second series: 90-year-old males (n = 29); one morning sample was collected. Testosterone values were determined using an iodine125-based radioimmunoassay kit modified for saliva., Results: Results show 1) a significant decrease in salivary testosterone values from 20s to 40s and older, 2) no significant decline after 40 through 90 years old, 3) no significant age-related differences in the degree of intraindividual diurnal fluctuation across age groups of 40-70s, and 4) higher BMI is associated with the lower salivary testosterone among 40-70s., Conclusions: These results suggest that neither a constant decrease of salivary testosterone values or markedly reduced intraindividual fluctations are universal aspects of aging. Older males may maintain relatively high testosterone levels compared to younger men and a relatively 'robust' neuroendocrinological system.

Background and Aims: Loss of muscle mass and gain of adipose tissue are hallmarks of aging among men in western populations. However, the extent to which these changes reflect inherent senescence is unclear. To determine age-related patterns of body composition and testosterone (T) among men in a subsistence population we sampled 104 nomadic and 102 settled men, ages 20+ years, among the Ariaal of northern Kenya., Methods: Anthropometric measures included height, weight, skinfolds, and waist circumference. Saliva samples, collected in the morning and afternoon, were assayed for T. Results were analyzed using general linear models, based on 10 year age groups., Results: Average overall BMI was 17.9+/-2.0 kg/m2. Settled and nomadic males did not differ in fat free mass (FFM). FFM peaked in the 30s with a significant decline in the oldest age group. Percent body fat and waist circumference increased significantly across age groups. Morning mean (+/-SD) salivary T was higher among settled males (107.6+/-57.6 vs 63.4+/-38.1 pmol/L; p<0.001), but did not differ significantly across age groups. Salivary T was positively related to suprailiac skinfolds, percent body fat and waist circumference among the settled males., Conclusions: Age-related patterns of body composition, but not salivary T, among Ariaal men are consistent with those observed in western populations. Together these results suggest that lower FFM after 60 may reflect senescent processes among human males, while age patterns of adiposity reflect energy balance. T does not appear to play an essential role in age-related patterns of body composition.

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., ((c) 2004 Wiley-Liss, Inc.)

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.

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.

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., (Copyright 2003 Wiley-Liss, Inc.)

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.

Objectives Extensive research has demonstrated that marriage and parenting are associated with lower testosterone levels in men, however, very little is known about associations with hormone concentrations in women. Two studies have found lower testosterone in relation to pair-bonding and motherhood in women, with several others suggesting that estradiol levels are lower among parous women than nulliparous women. Here, we examine estradiol and progesterone concentrations in relation to marriage and motherhood in naturally cycling, reproductive age women. Methods In 185 Norwegian women, estradiol and progesterone concentrations were assayed from waking saliva samples collected daily over the course of a menstrual cycle. Cycles were aligned on day 0, the day of ovulation. Mean periovulatory estradiol (days −7 to +6) and luteal progesterone (day +2 to +10) indices were calculated. Marital status and motherhood (including age of youngest child) were reported in baseline questionnaires. Multivariable linear regression models were used to examine associations between ovarian hormones, marital status, and motherhood. Results Women who were married or living as married had higher estradiol than unmarried women ( β = 0.19; 95% CI: 0.02, 0.36) and higher luteal progesterone as well ( β = 0.19; 95% CI: −0.01, 0.39). There were no notable differences in hormone levels in relationship to motherhood status. Conclusions Our results indicate that ovarian steroid hormones may be higher among women who are married or living as married, and suggest several possible explanations, however, additional research is needed to elucidate any causal relationships. Am. J. Hum. Biol. 27:501-507, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: Most research shows that fatherhood is related to reduced testosterone (T) levels, but relationships between the number of children and T levels are not addressed. In humans, paternal care usually involves obtaining adequate resources to support children, which may require engaging in male–male competition and maintaining high T levels. We hypothesize that T levels in fathers should increase with increasing family size. In 78 Polish men, aged 30 to 77 years, the number of children was significantly correlated with paternal T levels, but the direction of this relationship was dependent on the fathers'' education. In agreement with our hypothesis, in men with below-college education, T levels increased with increasing number of children. In contrast, in men with college education, the number of children was negatively related to paternal T levels. Drop in T levels throughout the day tended to be less pronounced the more children fathers had, irrespective of their educational level. Our results suggest that a hypothesis of simple trade-offs between mating and parenting effort may be too simplistic to explain changes in testosterone response to parenting in human males. In order to understand functional response of changes in T levels, it is crucial to account for family size and socioeconomic factors. However, due to the cross-sectional study design, we cannot exclude the possibility that T levels influenced reproductive behavior (rather than vice versa) and thus the number of children produced by men. [Copyright &y& Elsevier]

In order to study the hormonal correlates of the tradeoff between mating and parenting effort in human males, we examined the salivary testosterone (T) levels of 58 Boston-area men who were either unmarried (n=29), married without children (n=14), or married with children (n=15). Additionally, we asked participants to complete a questionnaire that surveyed their demographic, marital, and parenting backgrounds. We tested the hypotheses that (1) T levels will be lower in married than in unmarried men and (2) married men with children will have lower T levels than unmarried men and married men without children. We also tested a series of hypotheses relating variation in parenting and spousal relationships to T. We found that married men with and without children had significantly lower evening T than unmarried men. No significant differences in T were found among the groups in morning samples. Among married men without children, higher scores on a “spousal investment” measure and more hours spent with a man''s wife on his last day off work were both associated with lower T levels. We suggest that lower T levels during the day among fathers may facilitate paternal care in humans by decreasing the likelihood that a father will engage in competitive and/or mating behavior. [Copyright &y& Elsevier]

Abstract: Among other things, sexual selection theory posits that in species with limited male parental investment, males should evolve biological mechanisms to competitively dominate or otherwise compete with one another. It is unclear whether such proposed mechanisms would influence status hierarchies in small human groups. We report the results of a study investigating possible effects of prenatal (index-to-ring finger length ratio or 2D:4D) and salivary testosterone, and masculine identification, on status among 71 male college students living in nine residential groups. The results indicate no role of either prenatal or salivary testosterone in maintaining status hierarchies in these groups. A possible explanation is that peer-assessed status in these groups was arrived at cooperatively rather than through dominance contests. [Copyright &y& Elsevier]