Salivary testosterone levels in men at a U.S. sex club

Testosterone's role in modulating human behaviors relevant to mating and parenting

Testosterone (T) is linked to human mating and parenting. Here, we comprehensively reviewed evidence on whether, in men and women, (1) basal T levels are related to mating and parenting behaviors, (2) T responds to reproduction-relevant cues, (3) acute changes in T map onto subsequent mating and parenting behaviors, and (4) single-dose exogenous T administration causally affects mating and parenting behaviors. We examined whether the available evidence supports trade-off interpretations of T's adaptive function whereby high T levels correspond to greater mating/reproductive effort and competition and low T levels to greater parenting effort and nurturance. We found mixed support for trade-off hypotheses, suggesting that T's function in modulating human mating and parenting might be more nuanced and highly dependent on context and individual trait differences. Results were largely similar for men and women, although studies with women were scarcer than those with men for most behaviors we reviewed.

Relationship between the 2D:4D and prenatal testosterone, adult level testosterone, and testosterone change: Meta-analysis of 54 studies

The ratio between the hands' second to the fourth finger (2D:4D) is commonly hypothesized to result from prenatal testosterone. The 2D:4D has also been hypothesized to relate to adult-level testosterone and, more recently, to the testosterone response to a challenging situation. In the present work, we tested these core assumptions. Drawing from, in total, 54 studies and 8077 participants, we investigated whether the 2D:4D is related to adult level testosterone (44 studies), testosterone change (6 studies), and prenatal testosterone (10 studies). We found no evidence of the relationship between the above testosterone types and digit ratios. Furthermore, there was no relationship between testosterone and the right and left 2D:4D, male and female 2D:4D, and the 2D:4D and testosterone measurement (i.e., measured in blood or saliva). However, we found some evidence that prenatal testosterone measured in amniotic fluid (but not cord blood) might be related to the digit ratios-further studies are necessary to validate this observation. In summary, considering the current state of knowledge, any conclusions drawn from the assumption of the digit ratios as the proxy for testosterone (prenatal, adult level, or testosterone change under a challenging situation) warrant great caution.

Exogeneous testosterone increases sexual impulsivity in heterosexual men

Testosterone has been hypothesized to promote sexual motivation and behavior. However, experimental evidence in healthy humans is sparse and rarely establishes causality. The present study investigated how testosterone affects delay of gratification for sexual rewards. We administered a single dose of testosterone to healthy young males in a double-blind, placebo-controlled, between-participant design (N = 140). Participants underwent a sexual delay discounting task, in which they made a choice between a variable larger-later option (i.e., waiting longer to view a sexual picture for a longer duration) and a smaller-sooner option (i.e., waiting for a fixed shorter period of time to view the same picture for a shorter duration). We found that testosterone administration increased preference for the smaller-sooner option and induced steeper discounting for the delayed option. These findings provide direct experimental evidence that rapid testosterone elevations increase impulsivity for sexual rewards and represent an important step towards a better understanding of the neuroendocrine basis of sexual motivation in humans.

Number of sexual partners and serum testosterone levels in a population-based sample of unpartnered heterosexual men

BACKGROUND

The relationship between men's testosterone levels and their sexual behaviors is unclear as existing studies find mixed results.

OBJECTIVES

The key objective of this study is to assess whether men's testosterone levels are affected by sexual behaviors, and to explore whether this relationship varies by age. Specifically, this study addresses the question: Are men's testosterone levels affected by the number of sexual partners they accrue?

METHODS

This analysis was based on a nationally-representative sample of 977 unpartnered heterosexual men between the ages of 20 and 65 in the United States. Serum testosterone levels were measured from blood samples using isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) and the number of sexual partners in the past 12 months was ascertained from an Audio Computer-Assisted Personal Self-Interview (ACASI). Using ordinary least squares regression, serum testosterone levels were predicted as a function of the number of sexual partners that men reported, sociodemographic characteristics, and factors known to affect endocrine regulation. An interaction term between the number of sexual partners in the past 12 months and age was included.

RESULTS

The correlation between the number of sexual partners in the past 12 months and testosterone levels is contingent upon age: The relationship is positive for younger men but negative for older men. Among 20-year-old unpartnered heterosexual men, an additional sexual partner in the past 12 months is associated with an increase of 5.55 ng/dL of testosterone (95% CI: 2.92, 8.19). This initial positive effect at age 20 is reduced by 0.25 ng/dL of testosterone (95% CI: -0.44, -0.06) with each year that men age.

CONCLUSION

Testosterone levels in men are related to reproductive behaviors, but the direction of this relationship changes as men age. This article is protected by copyright. All rights reserved.

Salivary Testosterone and Sexual Function and Behavior in Men and Women: Findings from the Third British National Survey of Sexual Attitudes and Lifestyles (Natsal-3)

Using data from the third British National Survey of Sexual Attitudes and Lifestyles (Natsal-3) we examined associations between salivary testosterone (Sal-T) and sexual function and behavior. Single morning saliva samples were self-collected from a subsample of participants aged 18-74 years and analyzed using mass spectrometry. 1,599 men and 2,123 women were included in the analysis (40.6% of those invited to provide a sample). We adjusted for confounders in a stepwise manner: in model 1 we adjusted for age only; model 2 for age, season and relationship status, and model 3 we added BMI and self-reported health. In the fully adjusted models, among men, Sal-T was positively associated with both partnered sex (vaginal sex and concurrent partners) and masturbation. Among women, Sal-T was positively associated with masturbation, the only association with partnered sex was with ever experience of same-sex sex. We found no clear association between Sal-T and sexual function. Our study contributes toward addressing the sparsity of data outside the laboratory on the differences between men and women in the relationship between T and sexual function and behavior. To our knowledge, this is the first population study, among men and women, using a mass spectrometry Sal-T assay to do so.

Hormonal response after masturbation in young healthy men - a randomized controlled cross-over pilot study

BACKGROUND

Hormones like testosterone play a crucial role in performance enhancement and muscle growth. Therefore, various attempts to increase testosterone release and testosterone concentration have been made, especially in the context of resistance training. Among practitioners, sexual activity (coitus and masturbation) a few hours before training is often discussed to result in increases of testosterone concentration and thus promote muscle growth. However, there is no evidence to support this assumption and the kinetics of the testosterone and cortisol response after sexual activity have not been adequately investigated. Therefore, the aim of this pilot-study was to examine the kinetics of hormone concentrations of total testosterone, free testosterone and cortisol and their ratios after masturbation. In a three-arm single blinded cross-over study, the effects of masturbation with visual stimulus were compared to a visual stimulus without masturbation and the natural kinetics in healthy young men.

RESULTS

The results showed a significant between-condition difference in free testosterone concentrations. Masturbation (p < 0.01) and a visual stimulus (p < 0.05) may seem to counteract the circadian drop of free testosterone concentrations over the day. However, no statistical change was observed in the ratios between total testosterone, free testosterone and cortisol.

CONCLUSIONS

It can be assumed that masturbation may have a potential effect on free testosterone concentrations but not on hormonal ratios. However, additional studies with larger sample sizes are needed to validate these findings.

Individual Differences in Testosterone and Self-Control Predict Compulsive Sexual Behavior Proneness in Young Males

The ability to control sexual urges and impulses is essential to achieve individual and social harmony. Failing to regulate sexual behavior can lead to the interference with daily life goals, sexual diseases transmission and moral violations, among others. The dual control model of sexual response proposes that an imbalance between sexual excitation and sexual inhibition mechanisms may lead to sexual dysregulation, thereby explaining problematic sexual behavior. Interindividual differences in self-control and testosterone levels are likely to modulate sexual regulation mechanisms, but these individual features have scarcely been studied in the context of compulsive sexual behavior. This study investigated the role of sexual excitation and inhibition, self-control and testosterone levels in predicting individuals' proneness to display compulsive sexual behavior. Seventy healthy young males provided a saliva sample for testosterone measurements and filled in questionnaires on self-control, sexual excitation, sexual inhibition, sexual compulsivity and sexual behavior. High testosterone levels and low self-control were associated with higher sexual compulsivity scores. Additionally, testosterone levels and sexual inhibition negatively predicted the frequency of sexual behavior with a partner. The results of our study highlight the joint role of psychological traits and testosterone levels in compulsive sexual behavior proneness, providing implications regarding the prevention and treatment of this condition in young males.

Is Ejaculation Frequency in Men Related to General and Mental Health? Looking Back and Looking Forward

Despite its relevance for human sexuality, literature on potential effects of ejaculation frequency and masturbation on general and mental health outcomes is sparse. Reasons for this knowledge gap include a general lack of interest, but also methodological challenges and still existing superstition. This paper reconciles literature from various fields to extract relevant information on how ejaculation frequency effects general and mental health outcomes. Culture-bound syndromes have been reported in countries still strictly tabooing or condemning masturbation. Masturbatory guilt describes a phenomenon in individuals experiencing a discrepancy between moral standards and own behavior with respect to masturbation. Abstinence is one aspect under study in the area of fertility treatment. Specific time frames and their respective implications on quality of sperm remain inconclusive. Limited temporal resolution capacities hamper the precise study of brain structures directly activated during ejaculation. The relation between ejaculation frequency and hormonal influences remains poorly understood. Future research that specifically addresses ejaculation frequency and potential mental and general health outcomes is needed. In contrast to extracting knowledge as a byproduct from other studies with a different focus, this enables sound study designs and could provide evidence-based results which could then be further discussed and interpreted.

Are Sexual Desire and Sociosexual Orientation Related to Men's Salivary Steroid Hormones?

Objective

Although it is widely assumed that men’s sexual desire and interest in casual sex (i.e., sociosexual orientation) are linked to steroid hormone levels, evidence for such associations is mixed.

Methods

We tested for both longitudinal and cross-sectional relationships between salivary testosterone, cortisol, reported sexual desire and sociosexuality in a sample of 61 young adult men, each of whom was tested weekly on up to five occasions.

Results

Longitudinal analyses showed no clear relationships between steroid hormones and self-reported sexual desire or sociosexual orientation. Cross-sectional analyses showed no significant associations between average hormone levels and self-reported sexual desire. However, some aspects of sociosexuality, most notably desire for casual sex, were related to men’s average hormone levels. Men with higher average testosterone reported greater desire for casual sex, but only if they also had relatively low average cortisol levels.

Conclusions

Our results support a Dual Hormone account of men’s sociosexuality, in which the combined effects of testosterone and cortisol predict the extent of men’s interest in casual sex. However, we did not detect compelling evidence for an association of within-subject hormone shifts and sexual desire or sociosexual orientation.

Electronic supplementary material

The online version of this article (10.1007/s40750-020-00148-y) contains supplementary material, which is available to authorized users.

Human reproductive behavior, life history, and the Challenge Hypothesis: A 30-year review, retrospective and future directions

The Challenge Hypothesis (Wingfield et al., 1990) originally focused on adult male avian testosterone elevated in response to same-sex competition in reproductive contexts. The purpose of the present paper is to demonstrate how the Challenge Hypothesis has shaped ideas about human life histories. We conduct a citation analysis, drawing upon 400 Google Scholar citations in the human literature to identify patterns in this body of scholarship. We cover key factors, such as context and personality traits, that help explain variable testosterone responses such as winning/losing to adult competitive behavior. Findings from studies on courtship and sexual behavior indicate some variation in testosterone responses depending on factors such as motivation. A large body of research indicates that male testosterone levels are often lower in contexts of long-term committed partnerships and nurturant fathering and aligned with variation in male mating and parenting effort. As the Challenge Hypothesis is extended across the life course, DHEA and androstenedione (rather than testosterone) appear more responsive to juvenile male competitive behavior, and during reproductive senescence, baseline male testosterone levels decrease just as male life history allocations show decreased mating effort. We discuss how research on testosterone administration, particularly in older men, provides causal insight into effects of testosterone in humans, and how this "natural experiment" can be viewed in light of the Challenge Hypothesis. We synthesize central concepts and findings, such as an expanded array of costs of testosterone that inform life history tradeoffs between maintenance and reproductive effort, and we conclude with directions for future research.

Putting the flight in "fight-or-flight": Testosterone reactivity to skydiving is modulated by autonomic activation

Sensation-seeking (SS) involves the tendency to pursue exciting activities, potentially including risky behaviors (e.g., substance use, risky sexual behavior). Testosterone is associated with cortisol, SS, and autonomic nervous system (ANS) functioning. Testosterone reactivity/recovery during sky-diving and its relationship to cortisol response, ANS response and SS were examined. Forty-four participants provided reactive saliva samples and autonomic activity data before, during and after sky-diving and as well as basal day saliva samples. Testosterone reactivity/recovery to skydiving was significantly greater than basal day measurements. Testosterone responsivity to skydiving was predicted by increased cortisol, increased sympathetic activity (heart rate) and reduced parasympathetic activity (RMSSD). Independent of physiological effects, increased SS predicted testosterone responsivity to skydiving. These data suggest that testosterone reactivity, and its relationship to ANS responsivity, may be associated with pleasurable responses to risky/intense situations. These data may be useful in developing novel intervention strategies for risky behaviors.

Assay validation of hair androgens across the menstrual cycle

INTRODUCTION

Saliva is a common noninvasive biofluid for measuring stress and sex hormones, yet one pressing limitation is that salivary hormones fluctuate momentarily, daily, and (for girls) across the menstrual cycle. Hair steroid assays are thought to provide a cumulative index which collapses across hormonal variability, potentially eliminating the confound of daily and menstrual cyclicity and thereby reflecting individual differences in average hormone levels. Here we seek to validate a hair bioassay methodology and test whether hair androgens accurately measure long-term, stable androgen levels in emerging adult women across two menstrual cycles.

METHODS

Hair samples were collected at the end of each menstrual cycle for two cycles, and saliva samples were collected in the morning once per week across two menstrual cycles (N = 11 women). Hair samples were segmented by 1 cm for the first 4 cm to reflect the hormone levels of the past four serial months. Hair samples were assayed using commercially-available enzyme-immuno-assays for testosterone and DHEA.

RESULTS

Hair androgen concentrations were significantly correlated with averaged saliva hormone levels (DHEA: r = .75, p < .05; Testosterone: r = .67, p < .05). With respect to hair hormone stability, there were significant correlations for almost all the pairs of two 1 cm hair segments collected in two months that corresponded to the same time period. Hair androgens in one segment were significantly correlated with those in next segment. Regarding salivary androgen stability, the intra-class correlation across the weekly saliva samples indicated that for DHEA 59% of the total variance was within person and 41% was between person; and for testosterone 91% of the total variance was between person, and only 9% within person.

DISCUSSION

Results suggest that a one-time measure of hair provides a valid and reliable estimate of average steroid levels across two months. Moreover, whereas saliva measures of androgen levels capture week-to-week fluctuations in steroids, hair samples provide information on individual differences in average exposure to steroids, across long periods of time, such as months. Results are encouraging that hair DHEA and testosterone reflects the cumulative hormonal concentration and can be used as a stable hormonal index. Results also indicate that it is feasible to collect the first 3-4 centimeters of hair for studies of stable hormone levels.

Digit ratio (2D:4D) moderates the change in handgrip strength on an aggressive stimulus: A study among Polish young adults

BACKGROUND

The ratio of the lengths of second finger (2D) to the fourth (4D) is a putative indicator of foetal hormonal exposure. The link between 2D:4D and physical strength or sports performance in not consistent. It was suggested that the association of 2D:4D with the sporting and physical ability is better demonstrated in the context of challenge and competition, either real or simulated. However the evidence is limited to a few studies till date.

AIM

The objective of this study was to assess whether an aggressive video show could increase muscular strength and if 2D:4D moderated such increase.

STUDY DESIGN

We compared outcome measures in two experimental conditions.

OUTCOME MEASURES

Lengths of second (2D) and fourth (4D) digits and their ratio (2D:4D) for both hands, height and weight, handgrip strength of both hands.

SUBJECTS

250 healthy young adults (76 female).

RESULTS

The mean left-, right- and average HGS values increased after aggressive video watching than after control blank screen show. The increase was higher in females compared to males. The increase was higher among the individuals with lower 2D:4D, more clearly among females.

CONCLUSIONS

The 2D:4D correlated negatively with HGS after exposure to challenge condition and this relationship is pronounced in females than males. Thus there is link between prenatal androgenisation and enhanced physical power in challenge situation.

Sport and male sexuality

The relationships between sport and sexuality in males are of great social and clinical interest, because of sports and motor activities that highly promote social and sexual relationships. Even if few literature exist, two main questions should be taken into account: whether and how physical exercise and sport positively or negatively influence sexual health and behavior and/or whether and how sexual behavior may affect a sub-sequent sport performance. Physical exercise and sport per se can influence, positively or negatively, the hypothalamic-pituitary-testicular axis function and, consequently, the individual's reproductive and/or sexual health. This depends on individual factors such as genetic and epigenetic ones and on different variables involved in the practice of sport activities (type of sport, intensity and duration of training, doping and drug use and abuse, nutrition, supplements, psychological stress, allostatic load, etc.). If well conducted, motor and sport activities could have beneficial effects on sexual health in males. Among different lifestyle changes, influencing sexual health, regular physical activity is fundamental to antagonize the onset of erectile dysfunction (ED). However, competitive sport can lead both reproductive and/or sexual tract damages and dysfunctions, transient (genital pain, hypoesthesia of the genitalia, hypogonadism, DE, altered sexual drive, etc.) or permanent (hypogonadism, DE, etc.), by acting directly (traumas of the external genitalia, saddle-related disorders in cyclists, etc.) or indirectly (exercise-related hypogonadism, drug abuse, doping, stress, etc.). Sexual activities shortly performed before a sport competition could differently influence sport performance. Due to the few existing data, it is advisable to avoid an absolute pre-competition sexual abstinence.

A review of human male field studies of hormones and behavioral reproductive effort

The purpose of this paper is to review field studies of human male hormones and reproductive behavior. We first discuss life history theory and related conceptual considerations. As illustrations, distinctive features of human male life histories such as coalitional aggression, long-term partnering and paternal care are noted, along with their relevance to overall reproductive effort and developmental plasticity. We address broad questions about what constitutes a human male field study of hormones and behavior, including the kinds of hormone and behavioral measures employed in existing studies. Turning to several sections of empirical review, we present and discuss evidence for links between prenatal and juvenile androgens and sexual attraction and aggression. This includes the proposal that adrenal androgens-DHEA and androstenedione-may play functional roles during juvenility as part of a life-stage specific system. We next review studies of adult male testosterone responses to competition, with these studies emphasizing men's involvement in individual and team sports. These studies show that men's testosterone responses differ with respect to variables such as playing home/away, winning/losing, and motivation. Field studies of human male hormones and sexual behavior also focus on testosterone, showing some evidence of patterned changes in men's testosterone to sexual activity. Moreover, life stage-specific changes in male androgens may structure age-related differences in sexual behavior, including decreases in sexual behavior with senescence. We overview the considerable body of research on male testosterone, partnerships and paternal care, noting the variation in social context and refinements in research design. A few field studies provide insight into relationships between partnering and paternal behavior and prolactin, oxytocin, and vasopressin. In the third section of the review, we discuss patterns, limitations and directions for future research. This includes discussion of conceptual and methodological issues future research might consider as well as opportunities for contributions in under-researched male life stages (juvenility, senescence) and hormones (e.g., vasopressin).

Why is digit ratio correlated to sports performance?

Second to fourth digit ratio is the ratio of second to fourth digit length. It has been known that digit ratio is sexually dimorphic in humans, such that males tend to have lower digit ratio (longer fourth digits relative to second digits) than females. Digit ratio is thought to be a biomarker of the balance between fetal testosterone (FT) and fetal estrogen (FE) in a relatively narrow developmental window at the end of the first trimester of pregnancy. On the contrary, the relationships between digit ratio and levels of sex steroids in adults are not clear. Most correlational studies between digit ratio and adult sex steroids have revealed that this association is statistically not significant. However, for many years, a lot of researches showed negative relationships between digit ratio and sports performance such as rugby, surfing, rowing, sprinting, endurance, and hand grip strength. Here, we discuss possible mechanisms about the relationships between digit ratio and sports performance.

Is Testosterone a Food for the Brain?

INTRODUCTION

Testosterone is fundamental for psychological, sexological, cognitive, and reproductive aspects, and its lack or reduction largely impacts the quality of life in males and females.

AIM

Therefore, the aim of this review is to describe the role of testosterone in the neurophysiology of the brain and related aspects regarding the quality of general and sexual life.

METHODS

We listed and discussed the principal studies on the role of testosterone in the brain regarding sexual health, psychopathological conditions, and the elderly. The search strategies were composed by the insertion of specific terms in PubMed regarding the main studies from January 2000 to June 2015.

MAIN OUTCOME MEASURES

Using a psychoneuroendocrinologic perspective, we considered 4 main sections: brain and testosterone, sexuality and testosterone, psychopathology and testosterone, and cognitive impairment and testosterone.

RESULTS

Much evidence on the neuroendocrinology of testosterone regarding brain activity, sexual function, psychological health, and senescence was found. In any case, it is known that testosterone deficiency negatively impacts quality of life, first, but not exclusively, through a central effect. Moreover, testosterone and androgen receptors are differently expressed according to age and gender. This aspect contributes to gender differences and to the dimorphic physiological role of this hormone.

CONCLUSION

A universal role for testosterone can be recognized: low levels of testosterone are associated with mental disorders, sexual dysfunction, and cognitive impairment in both sexes. Hence, physicians should carefully assess testosterone levels, not only in the management of sexual dysfunctions but also when seeking to help patients with severe mental or organic diseases.

Digit ratio (2D:4D) and salivary testosterone, oestradiol and cortisol levels under challenge: Evidence for prenatal effects on adult endocrine responses

BACKGROUND

Digit ratio (2D:4D) is a marker for prenatal sex steroids and a correlate of sporting performance. This association may exist because low 2D:4D is linked to high prenatal levels of testosterone (T) and low oestrogens (E). It was recently suggested that low 2D:4D, and particularly low right-left 2D:4D (or Dr-l), is a marker for T changes in response to physical and aggressive challenges. If correct, this link may in part explain the association between 2D:4D and sports performance.

AIMS

We tested this hypothesis in adults.

STUDY DESIGN

Three experimental treatments were completed using a randomised, cross-over design; (i) cycle sprints plus an aggressive video (S+V), (ii) aggressive video plus cycle sprints (V+S), and (iii) a control session.

SUBJECTS

24 healthy adults (12 men and 12 women).

OUTCOME MEASURES

Salivary T, oestradiol (E2) and cortisol (C) levels were measured on six occasions across each session and pooled for analysis.

RESULTS

The S+V treatment was associated with a rise in T and C levels, and Dr-l was significantly and negatively correlated with T and E2 with these effects confined to men. The right 2D:4D and Dr-l were also negatively correlated with the T/C ratio and Dr-l negatively related to the E2/C ratio in men during the S+V treatment.

CONCLUSIONS

We suggest that the hormonal responses to a challenge are programmed by prenatal levels of T and E with possible links to sporting performance in adulthood.

Digit Ratio (2D:4D): A Biomarker for Prenatal Sex Steroids and Adult Sex Steroids in Challenge Situations

Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. This ratio is considered to be a biomarker of the balance between fetal testosterone (T) and estrogen (E) in a narrow window of early ontogeny. Evidence for this assertion is derived from direct and indirect measures of prenatal hormonal exposure (in experimental animals, via amniotic fluid samples and in the study of sex-typical traits) in relation to 2D:4D. In contrast, the relationships between 2D:4D and levels of sex steroids in adults are less clear, as many correlational studies of 2D:4D and adult sex steroids have concluded that this association is statistically non-significant. Here, we suggest that in order to understand the link between 2D:4D and sex hormones, one must consider both fetal organizing and adult activating effects of T and E. In particular, we hypothesize that 2D:4D correlates with organizing effects on the endocrine system that moderate activating effects in adulthood. We argue that this is particularly evident in "challenging" conditions such as aggressive and sexual encounters, in which individuals show increased levels of T. We discuss this refinement of the 2D:4D paradigm in relation to the links between 2D:4D and sports performance, and aggression.

Do testosterone declines during the transition to marriage and fatherhood relate to men's sexual behavior? Evidence from the Philippines

Testosterone (T) is thought to help facilitate trade-offs between mating and parenting in humans. Across diverse cultural settings married men and fathers have lower T than other men and couples' sexual activity often declines during the first years of marriage and after having children. It is unknown whether these behavioral and hormonal changes are related. Here we use longitudinal data from a large study in the Philippines (n=433) to test this model. We show that among unmarried non-fathers at baseline (n=153; age: 21.5 ± 0.3 years) who became newly married new fathers by follow-up (4.5 years later), those who experienced less pronounced longitudinal declines in T reported more frequent intercourse with their partners at follow-up (p<0.01) compared to men with larger declines in T. Controlling for duration of marriage, findings were similar for men transitioning from unmarried to married (without children) (p<0.05). Men who remained unmarried and childless throughout the study period did not show similar T-sexual activity outcomes. Among newly married new fathers, subjects who had frequent intercourse both before and after the transition to married fatherhood had more modest declines in T compared to peers who had less frequent sex (p<0.001). Our findings are generally consistent with theoretical expectations and cross-species empirical observations regarding the role of T in male life history trade-offs, particularly in species with bi-parental care, and add to evidence that T and sexual activity have bidirectional relationships in human males.

Sexual fantasies and gender/sex: a multimethod approach with quantitative content analysis and hormonal responses

Research links explicit sexuality (e.g., physical attraction and pleasure) to high testosterone (T) and nurturance (loving contact) to low T. Engaging in sexual fantasy, which can include explicit sexual and nurturant elements, increases T in women but not in men. We examined whether individual differences in the explicit sexual and nurturant content of fantasy were linked with T or with estradiol (E2). In addition, we explored whether fantasy content differed or overlapped by gender/sex. Participants (26 women, 23 men) provided saliva samples for hormones before and after imagining a self-defined positive sexual encounter and responding to open-ended questions about the situation they imagined. We systematically content-coded responses for explicit sexual and nurturant content. In men, lower inclusion of nurturant content predicted larger T responses to fantasy. Fantasy content was not linked with T in women or with E2 in women or men. Women and men did not differ significantly in explicit sexual and nurturant content. Our findings suggest that individual experiences of fantasy as more or less nurturant affect T in men, provide support for the Steroid/Peptide Theory of Social Bonds, and highlight the value of integrating hormones and content analysis to investigate research questions relevant to sexuality and gender/sex.

Age-independent increases in male salivary testosterone during horticultural activity among Tsimane forager-farmers

Testosterone plays an important role in mediating male reproductive trade-offs in many vertebrate species, augmenting muscle and influencing behavior necessary for male-male competition and mating-effort. Among humans, testosterone may also play a key role in facilitating male provisioning of offspring as muscular and neuromuscular performance are deeply influenced by acute changes in testosterone. This study examines acute changes in salivary testosterone among 63 Tsimane men ranging in age from 16-80 (mean 38.2) years during one-hour bouts of tree-chopping while clearing horticultural plots. The Tsimane forager-horticulturalists living in the Bolivian Amazon experience high energy expenditure associated with food production, have high levels of parasites and pathogens, and display significantly lower baseline salivary testosterone than age-matched US males. Mixed-effects models controlling for BMI and time of specimen collection reveal increased salivary testosterone (p<0.001) equivalent to a 48.6% rise, after one hour of tree chopping. Age had no effect on baseline (p=0.656) or change in testosterone (p=0.530); self-reported illness did not modify testosterone change (p=0.488). A comparison of these results to the relative change in testosterone during a competitive soccer tournament in the same population reveals larger relative changes in testosterone following resource production (tree chopping), compared to competition (soccer). These findings highlight the importance of moving beyond a unidimensional focus on changes in testosterone and male-male aggression to investigate the importance of testosterone-behavior interactions across additional male fitness-related activities. Acutely increased testosterone during muscularly intensive horticultural food production may facilitate male productivity and provisioning.

Beyond masculinity: testosterone, gender/sex, and human social behavior in a comparative context

Largely based on pre-theory that ties high testosterone (T) to masculinity, and low T to femininity, high T is mainly studied in relation to aggression, mating, sexuality, and challenge, and low T with parenting. Evidence, however, fails to support this, and the social variability in T is better accounted for by a competition-nurturance trade-off as per the Steroid/Peptide Theory of Social Bonds (van Anders et al., 2011). Four key domains are discussed: adult-infant interactions, sexual desire, sexual behavior, and partnering. Empirical engagements with gender/sex are shown to lead to important insights over assumptions about masculinity-femininity. Humans are discussed within a comparative framework that attends to cross-species principles informed by human insights alongside human-specific particularities like social constructions, which are critical to evolutionary understandings of the social role of T. This paper thus integrates seemingly orthogonal perspectives to allow for transformative approaches to an empirically-supported social phenomenology of T.

The effect of mental rotation on changes in plasma testosterone and cortisol levels

Testosterone level has an influence on cognitive functions, especially spatial abilities. The relationship is, however, bidirectional and brain activity also affects testosterone levels. The aim of this study was to analyze the effects of an intensive 3D mental rotation task on testosterone levels in young healthy men and women. In the mental rotation task, men reached a higher top score (P=0.027) and total score (P=0.004) compared to women. In 8 out of 9 women (P=0.008) but not in men (P=0.129) testosterone levels decreased after one hour of mental rotation testing. A significant gender difference was shown (P<0.0001). In all women, plasma cortisol levels was significantly lower after testing (P=0.004). In men cortisol levels decreased in 7 out of 9 subjects (P=0.039). A significant gender difference was not found (P=0.19). No association was found in women between baseline testosterone levels and mental rotation total score (P=0.810). In men there was a positive correlation between baseline testosterone and mental rotation total score (P=0.015). A significant difference gender difference was seen in the association between testosterone and mental rotation score (P<0.05). Mental rotation stimuli caused significant changes in hormonal levels of testosterone and cortisol. A gender-specific response was detected in testosterone fluctuation.

Sexual thoughts: links to testosterone and cortisol in men

Sexual stimuli increase testosterone (T) or cortisol (C) in males of a variety of species, including humans, and just thinking about sex increases T in women. We investigated whether sexual thoughts change T or C in men and whether hormone measures (baseline, post-activity, and changes) correlate with psychological sexual arousal. We used the Imagined Social Situation Exercise to assess how hormones respond to and correlate with sexual thoughts and arousal relative to three control conditions: neutral, stressful, and positive. A total of 99 men provided a baseline saliva sample, imagined and wrote about a sexual or control situation, and provided a second saliva sample 15 min later. Results indicated that, for participants in the sexual condition, higher baseline and post-activity C corresponded to larger increases in self- reported sexual and autonomic arousal. Although sexual thoughts increased sexual arousal, they did not change T or C compared to control conditions. Our results suggest that sexual thoughts are not sufficient to change T or C in men, but C may facilitate sexual arousal by directing energy towards a sexual situation.

Does cosleeping contribute to lower testosterone levels in fathers? Evidence from the Philippines

Because cross-species evidence suggests that high testosterone (T) may interfere with paternal investment, the relationships between men's transition to parenting and changes in their T are of growing interest. Studies of human males suggest that fathers who provide childcare often have lower T than uninvolved fathers, but no studies to date have evaluated how nighttime sleep proximity between fathers and their offspring may affect T. Using data collected in 2005 and 2009 from a sample of men (n = 362; age 26.0 ± 0.3 years in 2009) residing in metropolitan Cebu, Philippines, we evaluated fathers' T based on whether they slept on the same surface as their children (same surface cosleepers), slept on a different surface but in the same room (roomsharers), or slept separately from their children (solitary sleepers). A large majority (92%) of fathers in this sample reported practicing same surface cosleeping. Compared to fathers who slept solitarily, same surface cosleeping fathers had significantly lower evening (PM) T and also showed a greater diurnal decline in T from waking to evening (both p<0.05). Among men who were not fathers at baseline (2005), fathers who were cosleepers at follow-up (2009) experienced a significantly greater longitudinal decline in PM T over the 4.5-year study period (p<0.01) compared to solitary sleeping fathers. Among these same men, baseline T did not predict fathers' sleeping arrangements at follow-up (p>0.2). These results are consistent with previous findings indicating that daytime father-child interaction contributes to lower T among fathers. Our findings specifically suggest that close sleep proximity between fathers and their offspring results in greater longitudinal decreases in T as men transition to fatherhood and lower PM T overall compared to solitary sleeping fathers.

Physical competition increases testosterone among Amazonian forager-horticulturalists: a test of the 'challenge hypothesis'

The challenge hypothesis posits that acute increases in testosterone (T) during male-male competition enhance performance and survivability while limiting the physiological costs of consistently high T. Human challenge hypothesis research focuses on young men in industrial populations, who have higher baseline T levels than men in subsistence populations. We tested whether the Tsimane, pathogenically stressed forager-horticulturalists of the Bolivian Amazon, would express acute T increases in response to physical competition. Saliva was collected from 88 Tsimane men (aged 16-59 years) before and after a competitive soccer match. Tsimane men had significantly lower baseline levels of T (β = -0.41, p < 0.001) when compared with age-matched United States (US) males. Linear mixed-effects models were used to establish that T increased significantly immediately following competition (β = 0.23, p < 0.001), remaining high 1 h later (β = 0.09, p = 0.007); equivalent to 30.1 and 15.5 per cent increases in T, respectively. We did not find larger increases in T among winners (p = 0.412), although T increases were positively associated with self-rated performance (β = 9.07, p = 0.004). These results suggest that despite lower levels of T than US males, Tsimane males exhibit acute increases in T at the same relative magnitude reported by studies in industrialized settings, with larger increases in T for those who report better individual performance.