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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]

Abstract: Fluctuating asymmetry (FA) is believed to reflect developmental stability and thus may serve as a marker of the biologic quality of individuals. To test the hypothesis that degree of FA is related to a woman''s potential fertility, we measured finger length together with levels of estradiol in saliva samples collected daily for an entire menstrual cycle in 171 Polish urban and rural women. We show that women who are more symmetrical, as assessed by the degree of inequality in the fourth-digit length of their right and left hands, have 13% higher average levels of estradiol over the menstrual cycle than less symmetrical women (19.4 and 17.1 pmol/l, respectively; p=.0001). Among urban women, mid-cycle levels of estradiol were 28% higher in the symmetrical group than in the asymmetrical group. Because higher hormone levels in women may lead to a substantial rise in the probability of conception, low FA may therefore be associated with increased fertility. [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]

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. [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]

Objective: To investigate possible short-term effects of voluntary weight loss on ovarian steroid profiles in young women, in light of better established long-term effects in older women. Design: We tested for an association of voluntary weight change over the course of a menstrual cycle with salivary E2 and P profiles in the same menstrual cycle. Setting: Students were recruited in a college residence hall, and they provided daily saliva samples to a researcher living nearby. Patient(s): The 65 women who participated were all college students and ranged in age between 18 and 23 years. Intervention(s): None. Main Outcome Measure(s): Weight was assessed in the first week of the menstrual cycle and first week of the following menstrual cycle. Estradiol and P were measured by radioimmunoassay in daily saliva samples. Result(s): We did not detect a suppressive effect of weight loss on the overall level of either hormone. However, we did find evidence for more distinct follicular and luteal E2 peaks in women who gained weight. Peak luteal P also arrived about 2 days earlier in women who gained weight. Conclusion(s): This finding adds to evidence that short-term response of ovarian function to weight loss in young women is less pronounced than long-term response in older women. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Objective: To examine associations between environmental exposure to perfluoroalkyl substances (PFASs) and ovarian hormone concentrations in naturally cycling women.Design: E2 and P were measured in saliva samples collected daily for a single menstrual cycle and concentrations of PFASs (including perfluoroctane sulfonate [PFOS] and perfluoroctanoic acid) were measured in serum samples collected during the same cycle.Setting: Not applicable.Patient(s): A total of 178 healthy, naturally cycling women, aged 25-35 years.Intervention(s): None.Main Outcome Measure(s): Mean follicular E2 (cycle days -7 to -1, where 0 is the day of ovulation); mean luteal P (cycle days +2 to 10).Result(s): Among nulliparous, but not parous women, PFOS concentrations were inversely associated with E2 (β = -0.025, 95% CI -0.043, -0.007) and P (β = -0.027, 95% CI -0.048, -0.007). Similar, but weaker results were observed for perfluorooctanesulfonic acid. No associations were observed between other PFASs (including perfluoroctanoic acid) and ovarian steroid concentrations, nor were any associations noted in parous women.Conclusion(s): Our results demonstrate that PFOS and perfluorooctanesulfonic acid may be associated with decreased production of E2 and P in reproductive age women. These results suggest a possible mechanism by which PFASs affect women's health, and underscore the importance of parity in research on PFASs and women's reproductive health. [ABSTRACT FROM AUTHOR]