Pharmacokinetics of testosterone and estradiol gel preparations in healthy young men

Testosterone administration decreases sensitivity to angry facial expressions in healthy males: A computational modeling approach

Previous research indicates that higher testosterone levels are related to increased aggressive and dominant behaviors, particularly in males. One possible mechanism for these hormone-behavior associations could involve threat perception. However, the causal influence of testosterone on men's recognition of threatening facial expressions remains unknown. Here, we tested the causal effect of exogenous testosterone on men's sensitivity to facial threat by combining a psychophysical task with computational modeling. We administered a single dose (150 mg) of testosterone or placebo gel to healthy young men (n = 120) in a double-blind, placebo-controlled, between-participant design. Participants were presented with morphed emotional faces mixing anger/fear and neutral expressions and made judgments about the emotional expression. Across typical regression analysis, signal detection analysis, and drift diffusion modeling, our results consistently showed that individuals who received testosterone (versus placebo) exhibited a lower perceived sensitivity to angry facial expressions. But we observed no significant effects of testosterone administration on fearful facial expressions. The findings indicate that testosterone attenuates sensitivity to facial threat, especially angry facial expressions, which could lead to a misestimation of others' dominance and an increase in one's own aggressive and dominant behaviors.

Effects of 24-hour oral estradiol-valerate administration on hormone levels in men and pre-menopausal women

In order to translate the findings from the vast animal literature on the effect of 17β-estradiol (E2) on brain and behavior to humans, a placebo-controlled pharmacological enhancement of E2 levels for at least 24 h is necessary. However, an exogenous increase in E2 for such a prolonged period might affect the endogenous secretion of other (neuroactive) hormones. Such effects would be of relevance for the interpretation of the effects of this pharmacological regimen on cognition and its neural correlates as well as be of basic scientific interest. We therefore administered a double dose of 12 mg of estradiol-valerate (E2V) to men and of 8 mg to naturally cycling women in their low-hormone phase, and assessed the concentration of two steroids critical to hormone regulation: follicle stimulating hormone (FSH) and luteinizing hormone (LH). We also assessed any changes in concentration of the neuroactive hormones progesterone (P4), testosterone (TST), dihydrotestosterone (DHT) and immune-like growth factor 1 (IGF-1). This regimen resulted in similar E2 levels in both sexes (saliva and serum). FSH and LH levels in both sexes were down-regulated to the same degree. P4 concentration decreased in both sexes only in serum but not saliva. TST and DHT levels dropped only in men whereas sex-hormone binding globulin was not affected. Finally, the concentration of IGF-1 decreased in both sexes. Based on previous studies on the effects of these neuroactive hormones, only the degree of downregulation of TST and DHT levels in men might have an impact on brain and behavior, which should be considered when interpreting the effects of the presented E2V regimes.

Testosterone administration modulates inequality aversion in healthy males: evidence from computational modeling

Fairness concerns play a prominent role in promoting cooperation in human societies. Social preferences involving fairness concern have been associated with individual testosterone levels. However, the causal effects of testosterone administration on fairness-related decision making remain to be elucidated. Here, we used a randomized, double-blind, between-participant design and administered testosterone or placebo gel to 120 healthy young men. Three hours after administration, participants performed a modified Dictator Game from behavioral economics, in which they were asked to choose one of two monetary allocations between themselves and anonymous partners. Participants were either in a position of advantageous inequality (i.e., endowed with more than others) or disadvantageous inequality (i.e., endowed with less than others). Computational modeling showed that inequality-related preferences explained behavior better than competing models. Importantly, compared with the placebo group, the testosterone group showed significantly reduced aversion to advantageous inequality but enhanced aversion to disadvantageous inequality. These findings suggest that testosterone facilitates decisions that prioritize selfish economic motives over fairness concerns, which in turn may boost status-enhancing behaviors.

Testosterone eliminates strategic prosocial behavior through impacting choice consistency in healthy males

Humans are strategically more prosocial when their actions are being watched by others than when they act alone. Using a psychopharmacogenetic approach, we investigated the endocrinological and computational mechanisms of such audience-driven prosociality. One hundred and ninety-two male participants received either a single dose of testosterone (150 mg) or a placebo and performed a prosocial and self-benefitting reinforcement learning task. Crucially, the task was performed either in private or when being watched. Rival theories suggest that the hormone might either diminish or strengthen audience-dependent prosociality. We show that exogenous testosterone fully eliminated strategic, i.e., feigned, prosociality and thus decreased submission to audience expectations. We next performed reinforcement-learning drift-diffusion computational modeling to elucidate which latent aspects of decision-making testosterone acted on. The modeling revealed that testosterone compared to placebo did not deteriorate reinforcement learning per se. Rather, when being watched, the hormone altered the degree to which the learned information on choice value translated to action selection. Taken together, our study provides novel evidence of testosterone's effects on implicit reward processing, through which it counteracts conformity and deceptive reputation strategies.

The Optimal Time-lag for Testosterone Challenge Research Based on Salivary Profiles Following Different Doses of Transdermal Testosterone Administrations

In recent decades, testosterone challenge research examining the effects of testosterone on human neuropsychological behaviors has rapidly grown with the development of a single-dose transdermal testosterone administration paradigm. However, the optimal time-lag between testosterone administration and behavioral measurement is not unified, partly hindering causal understanding of the "testosterone effect". The present study aimed to investigate the optimal time-lag through LC-MS/MS-based salivary profiles of ten biomarkers among healthy males following administration of different doses of transdermal testosterone (i.e., 450- and 150-mg [Androgel®]). Results revealed that testosterone administration significantly increased salivary testosterone levels, reaching maximum levels 2 hours after 450-mg testosterone administration and 1 hour after 150-mg testosterone administration, respectively. Salivary androstenedione and DHEA increased synchronously with testosterone following administration. Moreover, the ratios of testosterone to androstenedione, DHEA, estradiol, and of androstenedione to estrone significantly elevated 1 hour after testosterone administration. In contrast, salivary cortisol and cortisone were decreased over time due to circadian rhythm rather than testosterone administration. Consistent with previous serum studies, the present salivary findings recommended 1-hour post testosterone administration as the optimal time-lag to measure the effects of testosterone on human behaviors in transdermal testosterone challenge research.

Testosterone administration enhances the expectation and perception of painful and non-painful somatosensory stimuli

The influence of testosterone on pain perception remains inconsistent in the literature. This randomized, placebo-controlled, double-blind, crossover study investigated the effect of testosterone administration on perception and expectation of electrocutaneous stimulus. Thirty healthy male participants received a single dose of testosterone in one session and a placebo in the other session. For each session, they completed a pain-rating task in which a predictability cue was inserted before a painful or non-painful electocutaneous stimulus delivery, while neural activity was simultaneously recorded by a 64-channel electroencephalographic (EEG) system. Expected and perceived pain ratings, as well as event-related potentials (ERPs) to electocutaneous stimuli and prestimulus EEG oscillatory activities while expecting upcoming electocutaneous stimuli were comprehensively compared between testosterone and placebo sessions. Compared with the placebo session, participants in the testosterone session reported greater pain rating and exhibited greater amplitude of N1 component on ERPs when perceiving both painful and non-painful electrocutaneous stimuli. Mediation analysis revealed that testosterone enhanced the pain-intensity ratings via the N1 response to the electrocutaneous stimulus. Upon viewing the predictability cues after testosterone administration, expected pain intensity increased and spontaneous low-frequency α-oscillation power in the frontal region decreased. These results provide evidence that testosterone enhanced perception and expectation of somatosensory events, and that this was a general effect rather than pain-specific. A plausible explanation for these findings is that testosterone acts to increase vigilance and sustained attention levels, as evidenced by the decreased α-oscillation power. Thus, our findings support a causal role for testosterone in heightening the biological salience of incoming somatosensory information.

Effects of exogenous oxytocin and estradiol on resting-state functional connectivity in women and men

Possible interactions of the neuropeptide oxytocin and the sex hormone estradiol may contribute to previously observed sex-specific effects of oxytocin on resting-state functional connectivity (rsFC) of the amygdala and hippocampus. Therefore, we used a placebo-controlled, randomized, parallel-group functional magnetic resonance imaging study design and measured amygdala and hippocampus rsFC in healthy men (n = 116) and free-cycling women (n = 111), who received estradiol gel (2 mg) or placebo before the intranasal administration of oxytocin (24 IU) or placebo. Our results reveal significant interaction effects of sex and treatments on rsFC of the amygdala and hippocampus in a seed-to-voxel analysis. In men, both oxytocin and estradiol significantly decreased rsFC between the left amygdala and the right and left lingual gyrus, the right calcarine fissure, and the right superior parietal gyrus compared to placebo, while the combined treatment produced a significant increase in rsFC. In women, the single treatments significantly increased the rsFC between the right hippocampus and the left anterior cingulate gyrus, whereas the combined treatment had the opposite effect. Collectively, our study indicates that exogenous oxytocin and estradiol have different region-specific effects on rsFC in women and men and that the combined treatment may produce antagonistic effects.

Can testosterone modulate prosocial learning in healthy males? A double-blind, placebo-controlled, testosterone administration study

Testosterone is associated with both aggressive and prosocial behavior, which depend on the social context and the trade-off between self- and other-interest. However, little is known about the effects of testosterone on prosocial behavior in a context without such trade-offs. The present study aimed to investigate the effects of exogenous testosterone on prosocial behavior by using a prosocial learning task. Healthy male participants (n =120) received a single dose of testosterone gel in a double-blind, placebo-controlled, between-participants experiment. Participants performed a prosocial learning task in which they were asked to learn to gain rewards for three different recipients, i.e., self, other and computer, by choosing symbols associated with potential rewards. The results showed that testosterone administration increased the learning rates across all the recipient conditions (d_other = 1.57; d_self = 0.50; d_computer = 0.99). More importantly, participants in the testosterone group had a higher prosocial learning rate than those in the placebo group (d = 1.57). These findings suggest that testosterone generally enhances reward sensitivity and prosocial learning. The present study corroborates the social status hypothesis, according to which testosterone promotes status-seeking prosocial behavior when it is appropriate to the social context.

Exogenous estradiol and oxytocin modulate sex differences in hippocampal reactivity during the encoding of episodic memories

Considerable evidence supports sex differences in episodic memory. The hormones estradiol and oxytocin both affect episodic memory and may contribute to these sex differences, but possible underlying hormonal interactions have not been tested in a sample involving both sexes. To this end, we conducted a randomized, placebo-controlled, parallel-group functional magnetic resonance imaging (fMRI) study including healthy free-cycling women (n = 111) and men (n = 115). The fMRI session was conducted under four experimental conditions: 1. transdermal estradiol (2 mg) and intranasal oxytocin (24 IU), 2. transdermal placebo and intranasal oxytocin, 3. transdermal estradiol and intranasal placebo, 4. transdermal placebo and intranasal placebo. Participants were scanned during the encoding of positive, neutral, and negative scenes. Recognition memory was tested three days following the scanning sessions without additional treatments. Under placebo, women showed a significantly better recognition memory and increased hippocampal responses to subsequently remembered items independent of the emotional valence compared to men. The separate treatments with either hormone significantly diminished this mnemonic sex difference and reversed the hippocampal activation pattern. However, the combined treatments produced no significant effect. Collectively, the results suggest that both hormones play a crucial role in modulating sex differences in episodic memory. Furthermore, possible antagonistic interactions between estradiol and oxytocin could explain previously observed opposing hormonal effects in women and men.

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.

Single-dose testosterone administration modulates instant empathic responses to others' pain: An EEG study

Whether or not testosterone can impair empathy remains unclear in the literature. Given that empathic responses to others' emotional experiences depend strongly upon top-down controlled mechanisms of attention, here we investigated whether the effects of testosterone administration on pain empathy could be modulated by manipulating attention. We used a double-blind, placebo-controlled within-participant design, in which either testosterone or placebo was administrated in separate sessions. Images depicting painful or nonpainful scenes were presented to induce instant empathic responses. Experiment 1 adopted the pain-judgment and hands-counting tasks to direct attention toward painful or nonpainful aspect of the images, respectively. Experiment 2 employed the pain-rating task to estimate affective and cognitive aspects of pain empathy. When discriminating nonpainful aspects of the images in the hands-counting task, accuracies were lower and empathic late positive potential responses were greater in testosterone sessions than in placebo sessions. This suggested that testosterone enhanced empathic responses to task-irrelevant pain-related features, which interfered with task performance. When providing empathic ratings to the images in the pain-rating task, empathic event-related potentials in the early stage were only observed in the testosterone session. This suggested that testosterone facilitated automatic affective reactivity to others' pain when elaborately processing empathic stimuli. Nevertheless, when discriminating painful aspects of the images in the pain-judgment task, we did not observe any significant differences between the two sessions. These results demonstrated that testosterone effects on enhancing brain reactivity to empathic stimuli were dependent upon task demands deploying attention allocation. The enhancement likely arose from the altered brain state (e.g., increased vigilance and arousal levels) after testosterone administration, as evidenced by the reduced amplitude of spontaneous α-oscillation recorded before the onset of the images. It expands our understanding of the neurobiological mechanisms that affect empathy, and highlights the role of testosterone.

Social reputation influences on liking and willingness-to-pay for artworks: A multimethod design investigating choice behavior along with physiological measures and motivational factors

Art, as a prestigious cultural commodity, concerns aesthetic and monetary values, personal tastes, and social reputation in various social contexts—all of which are reflected in choices concerning our liking, or in other contexts, our actual willingness-to-pay for artworks. But, how do these different aspects interact in regard to the concept of social reputation and our private versus social selves, which appear to be essentially intervening, and potentially conflicting, factors driving choice? In our study, we investigated liking and willingness-to-pay choices using—in art research—a novel, forced-choice paradigm. Participants (N = 123) made choices from artwork-triplets presented with opposing artistic quality and monetary value-labeling, thereby creating ambiguous choice situations. Choices were made in either private or in social/public contexts, in which participants were made to believe that either art-pricing or art-making experts were watching their selections. A multi-method design with eye-tracking, neuroendocrinology (testosterone, cortisol), and motivational factors complemented the behavioral choice analysis. Results showed that artworks, of which participants were told were of high artistic value were more often liked and those of high monetary-value received more willingness-to-pay choices. However, while willingness-to-pay was significantly affected by the presumed observation of art-pricing experts, liking selections did not differ between private/public contexts. Liking choices, compared to willingness-to-pay, were also better predicted by eye movement patterns. Whereas, hormone levels had a stronger relation with monetary aspects (willingness-to-pay/ art-pricing expert). This was further confirmed by motivational factors representative for reputation seeking behavior. Our study points to an unexplored terrain highlighting the linkage of social reputation mechanisms and its impact on choice behavior with a ubiquitous commodity, art.

Epicutaneous Administration of 17β-Estradiol Induces Langerhans Cells Depletion

BACKGROUND

Langerhans cells (LC) number and function in mouse vaginal mucosa are affected by 17β-estradiol (E₂) application; nonetheless, its effect on epidermal LC has not been studied. The purpose of this study was to evaluate the effect of topical administration of E₂ on the number, phenotype, and migratory ability of LC in mouse skin.

METHODS

Ears of adult CD1 male mice were topically treated once with several doses. Immunohistochemical staining for CD207 and TUNEL staining were performed. LC migration to lymph nodes and the effect on the expression of costimulatory molecules on cultured dendritic cells (DC) were also evaluated.

RESULTS

E₂ decreased the number of CD207+ LC in a dose-dependent manner. One hour after treatment, 1 and 10 µg/mL E₂ significantly reduced the LC number by 21% and 26%, respectively, after two hours, the reduction was 23% and 41%, respectively. After 48 hours, LC recovered, and after 96 hours of treatment, the CD207+/MHCII+ DC numbers were increased in regional lymph nodes. However, CD86 and CD40 molecules were expressed at lower levels than in positive control. The TUNEL assay did not show apoptotic cells. Furthermore, in cultured DC, E₂ promoted a decrease in CD40 and CD86 expression and an increase in CD273, CD274, MHCII, and CCR7.

CONCLUSIONS

The topical administration of E₂ induced a transitory local diminution of LC population and a tolerogenic phenotype. This decrease in epidermal LC suggests that E₂ may affect skin immune responses, inducing an inhibitory response, which should be considered when prescribing topical E₂ medications.

Sex differences in economic decision-making: Exogenous estradiol has opposing effects on fairness framing in women and men

Burgeoning evidence indicates that women are more sensitive to the context of an offer and show a stronger propensity to adjust their behavior with changing fairness frames. We evaluated whether the sex hormone estradiol and associated stereotypical beliefs contribute to fairness framings by administering topical estradiol (2 mg) to 108 healthy women and 104 heathy men in a randomized, double-blind, placebo-controlled between-subject study design. Participants played the role of the responder in a modified version of the Ultimatum Game (UG), in which identical offers for the division of a given amount of money were framed as either fair or unfair. Furthermore, participants completed an unframed UG and a delayed discounting task to probe possible effects of estradiol on altruistic preferences and delay gratification. Our results show that women were more sensitive to fairness frames than men. Intriguingly, however, estradiol had sex-specific effects on fairness sensitivity by increasing the acceptance rate of proposals with a fair frame in men and reducing it in women. Furthermore, the mere belief of receiving estradiol treatment significantly increased the acceptance of unfair-framed offers in both sexes, but estradiol did not significantly alter the response to unframed offers and impulsive decision-making. Collectively, our findings indicate that estradiol has opposing effects on the sensitivity to the perceived fairness of economic offers in women and men. The profound effects of estradiol treatment and stereotypical beliefs provide support for the notion that sex differences in fairness framing are rooted in both biological and environmental factors.

The effect of testosterone on economic risk-taking: A multi-study, multi-method investigation

Testosterone has been suggested to influence individuals' economic decision making, yet the effects of testosterone on economic behavior are not well-understood and existing research is equivocal. In response, in three studies, we examined the extent to which testosterone affected or was associated with several different facets of economic decision making. Study 1 was a double-blind, placebo-controlled, within-subjects study examining loss aversion and risk-taking (N = 26), whereas Study 2 was a larger double-blind, placebo-controlled, between-subjects study examining loss aversion and risk-taking behavior (N = 117). As a methodological compliment, Study 3 was a larger correlational design (N = 213) with a highly accurate measure of endogenous testosterone examining a wider range of economic behaviors and trait-like preferences. Broadly, the results of all three studies suggest no consistent relationship between testosterone and financial behavior or preferences. Although there were significant effects in specific cases, these findings did not replicate in other studies or would not remain significant when controlling for family-wise error rate. We consider potential contextual moderators that may determine under what circumstances testosterone affects economic decision making.

A causal role of estradiol in human reinforcement learning

The sex hormone estradiol is hypothesized to play a key role in human cognition, and reward processing specifically, via increased dopamine D1-receptor signalling. However, the effect of estradiol on reward processing in men has never been established. To fill this gap, we performed a double-blind placebo-controlled study in which men (N = 100) received either a single dose of estradiol (2 mg) or a placebo. Subjects performed a probabilistic reinforcement learning task where they had to choose between two options with varying reward probabilities to maximize monetary reward. Results showed that estradiol administration increased reward sensitivity compared to placebo. This effect was observed in subjects' choices, how much weight they assigned to their previous choices, and subjective reports about the reward probabilities. Furthermore, effects of estradiol were moderated by reward sensitivity, as measured through the BIS/BAS questionnaire. Using reinforcement learning models, we found that behavioral effects of estradiol were reflected in increased learning rates. These results demonstrate a causal role of estradiol within the framework of reinforcement learning, by enhancing reward sensitivity and learning. Furthermore, they provide preliminary evidence for dopamine-related genetic variants moderating the effect of estradiol on reward processing.

Not giving up: Testosterone promotes persistence against a stronger opponent

Recent research suggests that when we lack a sense of control, we are prone to motivational failures and early quitting in competitions. Testosterone, on the other hand, is thought to boost competitiveness. Here we investigate the interaction between these factors, testing the testosterone's potential to enhance persistence in a competition against a stronger opponent, depending on experimentally manipulated perceived control. Healthy participants were administered a single dose of testosterone or placebo. They first underwent a task designed to either induce low or high perceived control and then entered a costly competition against a progressively stronger opponent that they could quit at any time. In the placebo group, men with low perceived control quitted twice as early as those with high perceived control. Testosterone countered this effect, making individuals with low control persist in the competition for as long as those with high perceived control, and did so also despite raising participants' explicit awareness of the opponents' advantage. This psychoendocrinological effect was not modulated by basal cortisol levels, CAG repeat polymorphism of the androgen receptor gene, or trait dominance. Our results provide the first causal evidence that testosterone promotes competitive persistence in humans and demonstrate that this effect depends on the psychological state elicited prior to the competition, broadening our understanding of the complex relationships between testosterone and social behaviors.

Single dose testosterone administration enhances novelty responsiveness and short-term habituation in healthy males

The role of testosterone in sensory perception suggests that testosterone likely regulates adaptive responses to sensory changes, including habituation to repeated events and responsiveness to novel events. To test this hypothesis, we investigated how testosterone modulates brain responses to rapid changes in sensory inputs. Using a double-blind, placebo-controlled, within-participant design, each participant received a single dose of either testosterone or placebo, and then completed a passive auditory oddball task in which infrequent deviant tones were embedded in a series of frequent standard tones. Analysis of novelty-evoked potentials revealed smaller Mismatch Negativity (MMN) responses, but larger P3a responses in the testosterone session than in the placebo session. This suggests testosterone attenuates MMN responses that are associated with pre-attentive novelty detection and enhances P3a responses that are associated with involuntary attentional orientation toward novelty. Along with the repetition of standard tones, P2 responses on the auditory evoked potentials became significantly attenuated in the testosterone session, but not in the placebo session. This suggests testosterone enhances short-term habituation of P2 responses to recurring sensory events, which has been associated with bottom-up attention allocation. Mediation analysis further revealed that the role of testosterone in promoting attentional orientation toward novelty could be explained by the influence it exerts on short-term habituation and pre-attentive novelty detection. Overall, testosterone facilitated involuntary attention switching-withdrawal of attention from repeated sensory events and orientation toward novel sensory events-at the cost of attenuated pre-attentive novelty detection. This finding provides insight into the interplay between endocrinology and involuntary attentional processes.

Testosterone reduces generosity through cortical and subcortical mechanisms

Recent evidence has linked testosterone, a major sex hormone, to selfishness in economic decision-making. Here, we aimed to investigate the neural mechanisms through which testosterone reduces generosity by combining functional MRI with pharmacological manipulation among healthy young males in a double-blind, placebo-controlled, between-subject design. After testosterone or placebo gel administration, participants performed a social discounting task in which they chose between selfish options (benefiting only the participant) and generous options (providing also some benefit to another person at a particular social distance). At the behavioral level, testosterone reduced generosity compared to the placebo. At the neural level (n = 60), the temporoparietal junction (TPJ) encoded the other-regarding value of the generous option during generous choices, and this effect was attenuated by testosterone, suggesting that testosterone reduced the consideration of other's welfare as underpinned by TPJ activity. Moreover, TPJ activity more strongly reflected individual differences in generosity in the placebo than the testosterone group. Furthermore, testosterone weakened the relation between the other-regarding value of generous decisions and connectivity between the TPJ and a region extending from the insula into the striatum. Together, these findings suggest that a network encompassing both cortical and subcortical components underpins the effects of testosterone on social preferences.

Exogenous testosterone decreases men's sensitivity to vocal cues of male dominance

Assessing dominance is important for effective social interactions, and prior research suggests that testosterone is associated with men's dominance perceptions. The present study tested for a causal effect of exogenous testosterone on men's sensitivity to vocal cues of other men's dominance, an important parameter in male-male competition across species. One hundred and thirty-nine Chinese men received a single dose (150 mg) of testosterone or placebo gel in a double-blind, placebo-controlled, between-participant design. Participants reported their own dominance and judged other men's dominance from voices. Men's dominance sensitivity was significantly weaker in the testosterone group compared to those in the placebo group. Moreover, men's dominance sensitivity was negatively associated with their self-reported dominance in our Chinese sample, consistent with findings from Western populations. These results indicate that exogenous testosterone has a causal effect in decreasing men's dominance sensitivity, consistent with the Challenge Hypothesis, suggesting that the fluctuation of testosterone concentration mediates individuals' behaviors. Additionally, the present study could motivate further work on vocal assessment in the context of competition in humans and other species.

Single dose testosterone administration modulates the temporal dynamics of distractor processing

Some evidence suggests that testosterone can increase attentional orientation toward biologically relevant stimuli and increase sustained attention during goal-oriented behaviors. While rare irregular distractors often capture attention involuntarily and distract us away from the task at hand, we hypothesized that testosterone might (1) facilitate attentional orientation to novel distractors that are of potential behavioral relevance and (2) inhibit information processing of distractors that are irrelevant to the task. To test this hypothesis, we investigated the effects of testosterone on distractor processing in a novelty oddball task, during which infrequent target and distractor sounds were interspersed within a series of frequent non-target sounds. Using a double-blind, placebo-controlled within-participant design, we administered a single dose of either testosterone or placebo to 34 healthy male volunteers and compared their electroencephalographic responses to distractors. Increased amplitude of the early (260-310 ms) P3 component-which has been associated with phasic arousal and alertness triggered by novel stimuli-was observed in the testosterone session than in the placebo session. This early-P3 response mediated the effect of testosterone administration on target hit rate during the task. In addition, less α-oscillation suppression-which has been associated with the inhibition of task-irrelevant information processing-was observed in response to distractors later (538-757 ms) in the testosterone session than in the placebo session. These results suggest that testosterone facilitated phasic arousal to novel distractors during the early-latency stage, which might have influenced behavioral performance during the task. Furthermore, testosterone inhibited task-irrelevant information processing during the late-latency stage, which allowed better reorientation of attention back to the primary task. Our findings highlight the role of testosterone in distractor processing, and provide a theoretical basis for treating attention-related behavioral disorders with hormone therapies.

Exogenous testosterone increases the audience effect in healthy males: evidence for the social status hypothesis

Several studies have implicated testosterone in the modulation of altruistic behaviours instrumental to advancing social status. Independent studies have also shown that people tend to behave more altruistically when being watched (i.e. audience effect). To date, little is known about whether testosterone could modulate the audience effect. In the current study, we tested the effect of testosterone on altruistic behaviour using a donation task, wherein participants were asked to either accept or reject a monetary transfer to a charity organization accompanying a personal cost either in the presence or absence of an observer. We administered testosterone gel or placebo to healthy young men (n = 140) in a double-blind, placebo-controlled, mixed design. Our results showed that participants were more likely to accept the monetary transfer to the charity when being observed compared to when they completed the task alone. More importantly, this audience effect was amplified among people receiving testosterone versus placebo. Our findings suggest that testosterone administration increases the audience effect and further buttress the social status hypothesis, according to which testosterone promotes status-seeking behaviour in a context-dependent manner.

The effects of testosterone on the physiological response to social and somatic stressors

Higher testosterone levels in males have previously been linked to decreased stress reactivity, but in other cases, testosterone has been reported to increase the stress response. We addressed these inconsistencies in a placebo-controlled single-dose testosterone administration study, in which 120 male participants were randomly assigned to undergo a cold-pressor test (CPT, a non-social somatic stressor), a socially evaluated cold-pressor test (SECPT, a social-somatic stressor), or a lukewarm water test (LWT, a non-stressful control condition). Throughout the experiment, blood pressure and interbeat intervals were measured continuously, and saliva samples for hormonal analyses were taken repeatedly at predefined time points. When comparing the groups treated with placebo, the SECPT elicited a larger increase in the systolic blood pressure than CPT, in agreement with previous studies. However, testosterone administration altered this pattern. Compared to placebo, testosterone increased systolic blood pressure during the CPT, whereas the opposite effect was found during the SECPT. Cortisol reactivity was not affected by testosterone administration. The CAG repeat polymorphism of the androgen receptor gene was unrelated to the effects of testosterone on the stress response, but it was correlated with blood pressure across the whole sample. Our findings demonstrate that testosterone's effects on the stress response are dependent on the social context. Testosterone's ability to flexibly influence the response to stressors may be an important mechanism through which the hormone promotes adaptive behavior. Our results are also in line with research showing that testosterone decreases social anxiety and suggest it may help to modulate the effects of stress in socially challenging situations.

Testosterone administration in human social neuroendocrinology: Past, present, and future

Over the past 20 years, social neuroendocrinology researchers have developed pharmacological challenge paradigms to assess the extent to which testosterone plays a causal role in human psychological and behavioural processes. The current paper provides a brief summary of this research and offers recommendations for future research examining the neuroendocrine mechanisms underlying human behaviour.

Screening and identification of salivary biomarkers for assessing the effects of exogenous testosterone administration on HPG and HPA axes and ECS

The contents of steroids and endocannabinoids along with the ratios between them would be candidate biomarkers for sensitively and comprehensively assessing the role of testosterone in regulating the activities of the hypothalamus-pituitary-gonadal (HPG) axis, the hypothalamus-pituitaryadrenal (HPA) axis and endogenous cannabinoid system (ECS). However, previous studies mostly used the contents rather than the ratios as biomarkers. This study aimed to systematically screen and identify sensitive biomarkers from 21 candidates including both the contents of nine steroids and one endocannabinoid and their ratios in saliva. Three screening criteria were whether there were intergroup differences, time-dependent changes and considerable relative stability during a 4-h period after exogenous testosterone administration. This study used LC-APCI⁺-MS/MS to determine the salivary levels of the candidate biomarkers on 62 male healthy undergraduates who were divided into testosterone administration and placebo control groups. The results revealed that salivary testosterone, androstenedione, DHEA and the ratios of testosterone to estradiol and AEA, and of cortisol to testosterone and DHEA were sensitive biomarkers for assessing the effects of testosterone administration on the three neuroendocrine systems because they all showed significant intergroup differences and time-dependent changes and good relative stability. Salivary cortisol, cortisone and the ratios of testosterone to androstenedione and DHEA and of androstenedione to estrone, and of cortisol to cortisone, androstenedione and AEA might be suitable biomarkers because they met only two of the three criteria, but needed to be validated in the future. The rest biomarkers were unsuitable because they mostly showed no significant intergroup differences, blunt time-dependent changes and poor relative stability.

Single dose testosterone administration increases men's facial femininity preference in a Chinese population

Sex hormones are thought to influence human mate preferences. Previous studies have reported mixed results regarding the association between men's testosterone levels and their mate preferences. The present study investigated the effect of testosterone administration on men's facial femininity preference. Heterosexual Chinese male participants (n = 140) received a single dose of 150 mg testosterone or placebo gel in a double-blind, placebo-controlled, between-participant design. Results showed that Chinese men demonstrated general preferences for feminized women's faces, consistent with previous results from the Western population. More importantly, men showed stronger attraction to femininity in women's faces three hours after testosterone administration than at the beginning of the session. In the placebo group, no significant change in facial femininity preferences was found between time points. These results indicate that exogenous testosterone increases men's facial femininity preferences in a Chinese population.

Current approach to the clinical care of adolescents with gender dysphoria

Over the last decade, we have witnessed a significant rise in the number of transgender young people seeking endocrine treatment, of which clinical service and gender dysphoria terminology have attempted to keep pace both in matching demand and better describing the condition. Although helpful guidelines for pubertal suppression and gender affirming hormones have been developed, uncertainties remain regarding treatment and monitoring during treatment, often because the clinical needs of the transgender population have outpaced medical expertise and training. Recently, multidisciplinary team work has evolved due to the increasing complexity of diagnostic and treatment decision-making and has been instrumental in creating a unique service with input from a range of specialists. In this article, the current approach in clinical management of adolescents with gender dysphoria is reviewed, with focus on the endocrine aspect of care in children and adolescents. Questions on what defines optimal clinical care of children and adolescents with gender dysphoria remain and should be the focus of future research. (www.actabiomedica.it)

Exogenous testosterone increases status-seeking motivation in men with unstable low social status

Testosterone is associated with status-seeking behaviors such as competition, which may depend on whether one wins or loses status, but also on the stability of one's status. We examined (1) to what extent testosterone administration affects competition behavior in repeated social contests in men with high or low rank, and (2), whether this relationship is moderated by hierarchy stability, as predicted by the status instability hypothesis. Using a real effort-based design in healthy male participants (N = 173 males), we first found that testosterone (vs. placebo) increased motivation to compete for status, but only in individuals with an unstable low status. A second part of the experiment, tailored to directly compare stable with unstable hierarchies, indicated that exogenous testosterone again increased competitive motivation in individuals with a low unstable status, but decreased competition behavior in men with low stable status. Additionally, exogenous testosterone increased motivation in those with a stable high status. Further analysis suggested that these effects were moderated by individuals' trait dominance, and genetic differences assessed by the androgen receptor (CAG-repeat) and dopamine transporter (DAT1) polymorphisms. Our study provides evidence that testosterone specifically boosts status-related motivation when there is an opportunity to improve one's social status. The findings contribute to our understanding of testosterone's causal role in status-seeking motivation in competition behavior, and indicate that testosterone adaptively increases our drive for high status in a context-dependent manner. We discuss potential neurobiological pathways through which testosterone may attain these effects on behavior.

Single dose testosterone administration increases impulsivity in the intertemporal choice task among healthy males

Circulating levels of testosterone have been positively associated with impulsivity. The present study investigates the effect of testosterone administration on impulsivity in an intertemporal choice task, where participants are given a choice between smaller-sooner rewards and larger-later rewards. Healthy young male participants (n = 111) received a single-dose of 150 mg testosterone gel in a double-blind, placebo-controlled, between-subjects design. At 180 min post-administration, participants performed the decision-making task. Both model-free (i.e., higher indifference point) and model-based (i.e., steeper discounting rate) parameters revealed that testosterone administration increased impulsive choice. This finding supports the hypothesis that exogenous testosterone increases impulsivity among healthy young males in a laboratory task.

Serum Testosterone and Cortisol Concentrations After Single-Dose Administration of 100-Mg Transdermal Testosterone in Healthy Men

The growing interest in testosterone's effects on men's social behaviors, in particular aggressive, risk-taking, or status maintenance behaviors, is accompanied by a paucity of dose-dependent pharmacokinetic data. Examining the neurophysiological effects of transdermal testosterone typically includes a 4h delay before further brain-behavior measurements. Nevertheless, high heterogeneity regarding the timing of follow-up measurements and dosage remains. In a double-blind placebo-controlled design, we examined the short-term pharmacokinetic profile of 100-mg transdermal testosterone (Testotop^®) to determine the optimal time for detecting testosterone-mediated effects. Across two studies, 35 healthy men received a single dose of testosterone and placebo in two separate sessions. In study one (n = 16), serum testosterone and cortisol were assessed serially every 30 min up to 2 h posttreatment. In study two (n = 19), we assessed serum testosterone and cortisol at baseline, 2 h, and 4.15 h (255 min) posttreatment. Relative to baseline and placebo, transdermal testosterone significantly increased total serum testosterone concentrations 90 min posttreatment, reaching maximum concentration between 2 h and 3 h posttreatment. Albeit elevated, serum testosterone levels gradually decreased between 2 h and 4 h following treatment. Transdermal testosterone did not suppress cortisol release. Instead, cortisol concentrations decreased according to cortisol's known circadian rhythm. Unlike previous findings showing significant testosterone concentration increases as soon as 60 min and as late as 3 h post 150-mg testosterone treatment, our 100-mg testosterone manipulation significantly increased testosterone concentrations 90 min following treatment. These pharmacokinetic data are important in facilitating the optimization of timing parameters for future testosterone challenge studies.

Testosterone administration increases social discounting in healthy males

Although testosterone is thought to induce antisocial and aggressive behavior, research on social economic interactions has associated it with prosocial and affiliative behavior. Here, we investigated the effects of testosterone on social distance-dependent generosity in an economic discounting task where participants chose between selfish and generous alternatives. We administered testosterone gel or placebo to men in a double-blind, randomized design and measured how willing they were to share rewards with close and distant others. Across two studies (total n = 174), testosterone administration consistently increased social discounting, that is participants became more selfish, particularly with regard to distant others (vs. close others). This effect was not explained by testosterone-induced increases in social distance perception. Our findings provide causal evidence that-testosterone reduces generosity in human economic decision-making. Moreover, they suggest that the valuation and the perception of social distance are independently affected by testosterone.

Does testosterone impair men's cognitive empathy? Evidence from two large-scale randomized controlled trials

The capacity to infer others' mental states (known as 'mind reading' and 'cognitive empathy') is essential for social interactions across species, and its impairment characterizes psychopathological conditions such as autism spectrum disorder and schizophrenia. Previous studies reported that testosterone administration impaired cognitive empathy in healthy humans, and that a putative biomarker of prenatal testosterone exposure (finger digit ratios) moderated the effect. However, empirical support for the relationship has relied on small sample studies with mixed evidence. We investigate the reliability and generalizability of the relationship in two large-scale double-blind placebo-controlled experiments in young men (n = 243 and n = 400), using two different testosterone administration protocols. We find no evidence that cognitive empathy is impaired by testosterone administration or associated with digit ratios. With an unprecedented combined sample size, these results counter current theories and previous high-profile reports, and demonstrate that previous investigations of this topic have been statistically underpowered.

Exogenous Testosterone Increases Decoy Effect in Healthy Males

There is increasing interest in the role played by testosterone in economic decision-making and social cognition. However, despite the growing body of findings in this field of research, no empirical study to date has tested whether testosterone modulates decision-making when an asymmetrically dominated decoy option is introduced in a choice set. Within a choice set that comprises two options, an asymmetrically dominated decoy option is a third option that, when introduced in the choice set, is much worse than one of the existing options, but comparable to the other existing option. Introduction of a decoy option leads to a preference toward the dominating option (i.e., decoy effect). Healthy male participants (n = 63) received a single-dose of 150 mg testosterone gel in a double-blind, placebo-controlled, between-subjects design. At 180 min post-administration, participants took part in a decision-making task to elicit decoy effect. Results showed that participants in the testosterone group made less consistent choices and more target choices (i.e., decoy effect) than participants in the placebo group. These findings are interpreted in light of the dual-process theory and are in line with existing evidence suggesting that testosterone promotes more intuitive and automatic judgments in human decision-making.

Testing the influence of testosterone administration on men's honesty in a large laboratory experiment

The impact of testosterone on decision-making is a growing literature, with several reports of economically relevant outcomes. Similar to Wibral et al. (2012), we investigate the effects of exogenous testosterone administration on deception in a double-blind placebo controlled study. Participants (N = 242) were asked to roll a die in private and were paid according to their reported roll, which creates the opportunity to lie about the outcome to increase earnings. We find evidence for self-serving lying in both treatment and control groups and a statistically insignificant negative effect (d = −0.17, 95% CI[−0.42, 0.08]) indicating more honest behavior (i.e., lower reports) following testosterone administration. Although insignificant, the direction was the same as in the Wibral et al. study, and the meta-analytic effect of the two studies demonstrates lower reporting (i.e., more honesty) following testosterone (vs. placebo) administration, significant at the 0.05 level (d = −0.27, 95% CI[−0.49, −0.06]). We discuss how our results and methodology compare with Wibral et al. and identify potential causes for differences in findings. Finally, we consider several plausible connections between testosterone and lying that may be further investigated using alternative methodologies.

Human social neuroendocrinology: Review of the rapid effects of testosterone

Contribution to Special Issue on Fast effects of steroids. It is well documented that testosterone concentrations change rapidly within reproductively relevant contexts (e.g., competition, mate-seeking). It has been argued that such rapid changes in testosterone may serve to adaptively fine-tune ongoing and/or future social behaviour according to one's social environment. In this paper, we review human correlational and experimental evidence suggesting that testosterone fluctuates rapidly in response to competition and mate-seeking cues, and that such acute changes may serve to modulate ongoing and/or future social behaviours (e.g., risk-taking, competitiveness, mate-seeking, and aggression). Some methodological details, which limit interpretation of some of this human work, are also discussed. We conclude with a new integrative model of testosterone secretion and behaviour, the Fitness Model of Testosterone Dynamics. Although we focus primarily on human aggression in this review, we also highlight research on risk-taking, competitiveness, and mate-seeking behaviour.

Single-dose testosterone administration increases men's preference for status goods

In modern human cultures where social hierarchies are ubiquitous, people typically signal their hierarchical position through consumption of positional goods-goods that convey one's social position, such as luxury products. Building on animal research and early correlational human studies linking the sex steroid hormone testosterone with hierarchical social interactions, we investigate the influence of testosterone on men's preferences for positional goods. Using a placebo-controlled experiment (N = 243) to measure individuals' desire for status brands and products, we find that administering testosterone increases men's preference for status brands, compared to brands of similar perceived quality but lower perceived status. Furthermore, testosterone increases positive attitudes toward positional goods when they are described as status-enhancing, but not when they are described as power-enhancing or high in quality. Our results provide novel causal evidence for the biological roots of men's preferences for status, bridging decades of animal behavioral studies with contemporary consumer research.

Neuropsychopharmacological aesthetics: A theoretical consideration of pharmacological approaches to causative brain study in aesthetics and art

Recent developments in neuroaesthetics have heightened the need for causative approaches to more deeply understand the mechanism underlying perception, emotion, and aesthetic experiences. This has recently been the topic for empirical work, employing several causative methods for changing brain activity, as well as comparative assessments of individuals with brain damage or disease. However, one area of study with high potential, and indeed a long history of often nonscientific use in the area of aesthetics and art, employing psychopharmacological chemicals as means of changing brain function, has not been systematically utilized. This chapter reviews the literature on this topic, analyzing neuroendocrinological (neurochemical) approaches and mechanisms that might be used to causatively study the aesthetic brain. We focus on four relevant neuromodulatory systems potentially related to aesthetic experience: the dopaminergic, serotonergic, cannabinoid, and the opioidergic system. We build a bridge to psychopharmacological methods and review drug-induced behavioral and neurobiological consequences. We conclude with a discussion of hypotheses and suggestions for future research.

Short-term effects of transdermal estradiol in men undergoing androgen deprivation therapy for prostate cancer: a randomized placebo-controlled trial

OBJECTIVE

There is increasing recognition that, in men, some biological actions attributed to testosterone (TS) are mediated by estradiol (E2). This study used two low doses of daily transdermal E2 gel to assess the effects on circulating E2 concentrations in men with prostate cancer with suppressed endogenous E2 production arising from androgen deprivation therapy (ADT). Secondarily, we aimed to assess short-term biological effects of E2 add-back without increasing circulating TS.

DESIGN

28-day randomised, placebo-controlled trial.

METHODS

37 participants were randomised to either 0.9 or 1.8 mg of 0.1% E2 gel per day or matched placebo gel. Fasting morning serum hormones, quality of life questionnaires, and treatment side effects were evaluated at baseline, days 14 and 28. Hot flush diaries and other biochemical measurements were completed at baseline and study end.

RESULTS

Transdermal E2 significantly raised serum E2 from baseline to day 28 compared to placebo in the 0.9 mg dose group (median: 208 pmol/L; interquartile range: 157-332) and in the 1.8 mg dose group (median: 220 pmol/L; interquartile range: 144-660). E2 treatment reduced hot flush frequency and severity as well as beta carboxyl-terminal type 1 collagen telopeptide.

CONCLUSION

In men with castrate levels of E2 and TS, daily transdermal E2: 0.9-1.8 mg increased median serum E2 concentrations into the reference range reported for healthy men, but with substantial variability. E2 treatment reduced hot flushes and bone resorption. Larger studies will be required to test whether low-dose E2 treatment can mitigate ADT-associated adverse effects without E2-related toxicity.

Single dose testosterone administration modulates emotional reactivity and counterfactual choice in healthy males

Testosterone has been implicated in the regulation of emotional responses and risky decision-making. However, the causal effect of testosterone upon emotional decision-making, especially in non-social settings, is still unclear. The present study investigated the role of testosterone in counterfactual thinking: regret is an intense negative emotion that arises from comparison of an obtained outcome from a decision against a better, non-obtained (i.e. counterfactual) alternative. Healthy male participants (n = 64) received a single-dose of 150 mg testosterone Androgel in a double-blind, placebo-controlled, between-participants design. At 180 min post-administration, participants performed the counterfactual thinking task. We applied a computational model derived from behavioral economic principles to uncover latent decision-making mechanisms that may be invisible in simple choice analyses. Our data showed that testosterone increased the ability to use anticipated regret to guide choice behavior, while reducing choice based on expected value. On affective ratings, testosterone increased sensitivity to both obtained and counterfactual outcomes. These findings provide evidence that testosterone causally modulates emotional decision-making, and highlight the role of testosterone in affective sensitivity.

Exogenous testosterone enhances cortisol and affective responses to social-evaluative stress in dominant men

Stress often precedes the onset of mental health disorders and is linked to negative impacts on physical health as well. Prior research indicates that testosterone levels are related to reduced stress reactivity in some cases but correlate with increased stress responses in other cases. To resolve these inconsistencies, we tested the causal influence of testosterone on stress reactivity to a social-evaluative stressor. Further, prior work has failed to consider status-relevant individual differences such as trait dominance that may modulate the influence of testosterone on responses to stressors. Participants (n=120 males) were randomly assigned to receive exogenous testosterone or placebo (n=60 testosterone treatment group) via topical gel prior to a well-validated social-evaluative stressor. Compared to placebo, testosterone significantly increased cortisol and negative affect in response to the stressor, especially for men high in trait dominance (95% confidence intervals did not contain zero). The findings suggest that the combination of high testosterone and exposure to status-relevant social stress may confer increased risk for stress-mediated disorders, particularly for individuals high in trait dominance.

Exogenous testosterone in a non-social provocation paradigm potentiates anger but not behavioral aggression

Animal studies suggest a causal link between testosterone and aggression. However, in human research the exact role of this hormone is still unclear, having been linked to dominance and approach behavior rather than to aggression per se. In a social context, the induction of aggression might be confounded with dominance or status changes, which potentially influence the association between aggression and testosterone. The objective of the current study was to investigate the influence of testosterone on non-social aggression in a double-blind, placebo-controlled experiment including 90 healthy male participants. To this end, we developed an innovative paradigm in which participants were provoked by a malfunctioning joystick restraining them from a promised reward. As measures for aggression throughout the task the joystick amplitude was recorded and anger was assessed via emotional self-ratings. Participants reacted to the provocation with a significant shift to more negative emotions and increased implicit aggressive behavior, reflected in the force exerted to pull the joystick following provocation. Importantly, the study demonstrated first evidence for a modulating influence of testosterone on non-social aggression in males: Self-rated anger was significantly elevated in the testosterone group compared to the placebo group as a function of provocation. Testosterone administration did not significantly influence the implicit aggressive response. These findings demonstrate a potentiating effect of testosterone on provocation-related anger in a non-social context. Furthermore, the results highlight the importance of disentangling different components of aggression and characterizing different influencing factors when inferring on hormonal effects.

Endocrine Treatment of Gender-Dysphoric/Gender-Incongruent Persons: An Endocrine Society Clinical Practice Guideline

OBJECTIVE

To update the "Endocrine Treatment of Transsexual Persons: An Endocrine Society Clinical Practice Guideline," published by the Endocrine Society in 2009.

PARTICIPANTS

The participants include an Endocrine Society-appointed task force of nine experts, a methodologist, and a medical writer.

EVIDENCE

This evidence-based guideline was developed using the Grading of Recommendations, Assessment, Development, and Evaluation approach to describe the strength of recommendations and the quality of evidence. The task force commissioned two systematic reviews and used the best available evidence from other published systematic reviews and individual studies.

CONSENSUS PROCESS

Group meetings, conference calls, and e-mail communications enabled consensus. Endocrine Society committees, members and cosponsoring organizations reviewed and commented on preliminary drafts of the guidelines.

CONCLUSION

Gender affirmation is multidisciplinary treatment in which endocrinologists play an important role. Gender-dysphoric/gender-incongruent persons seek and/or are referred to endocrinologists to develop the physical characteristics of the affirmed gender. They require a safe and effective hormone regimen that will (1) suppress endogenous sex hormone secretion determined by the person's genetic/gonadal sex and (2) maintain sex hormone levels within the normal range for the person's affirmed gender. Hormone treatment is not recommended for prepubertal gender-dysphoric/gender-incongruent persons. Those clinicians who recommend gender-affirming endocrine treatments-appropriately trained diagnosing clinicians (required), a mental health provider for adolescents (required) and mental health professional for adults (recommended)-should be knowledgeable about the diagnostic criteria and criteria for gender-affirming treatment, have sufficient training and experience in assessing psychopathology, and be willing to participate in the ongoing care throughout the endocrine transition. We recommend treating gender-dysphoric/gender-incongruent adolescents who have entered puberty at Tanner Stage G2/B2 by suppression with gonadotropin-releasing hormone agonists. Clinicians may add gender-affirming hormones after a multidisciplinary team has confirmed the persistence of gender dysphoria/gender incongruence and sufficient mental capacity to give informed consent to this partially irreversible treatment. Most adolescents have this capacity by age 16 years old. We recognize that there may be compelling reasons to initiate sex hormone treatment prior to age 16 years, although there is minimal published experience treating prior to 13.5 to 14 years of age. For the care of peripubertal youths and older adolescents, we recommend that an expert multidisciplinary team comprised of medical professionals and mental health professionals manage this treatment. The treating physician must confirm the criteria for treatment used by the referring mental health practitioner and collaborate with them in decisions about gender-affirming surgery in older adolescents. For adult gender-dysphoric/gender-incongruent persons, the treating clinicians (collectively) should have expertise in transgender-specific diagnostic criteria, mental health, primary care, hormone treatment, and surgery, as needed by the patient. We suggest maintaining physiologic levels of gender-appropriate hormones and monitoring for known risks and complications. When high doses of sex steroids are required to suppress endogenous sex steroids and/or in advanced age, clinicians may consider surgically removing natal gonads along with reducing sex steroid treatment. Clinicians should monitor both transgender males (female to male) and transgender females (male to female) for reproductive organ cancer risk when surgical removal is incomplete. Additionally, clinicians should persistently monitor adverse effects of sex steroids. For gender-affirming surgeries in adults, the treating physician must collaborate with and confirm the criteria for treatment used by the referring physician. Clinicians should avoid harming individuals (via hormone treatment) who have conditions other than gender dysphoria/gender incongruence and who may not benefit from the physical changes associated with this treatment.

The Effect of Testosterone Administration and Digit Ratio (2D:4D) on Implicit Preference for Status Goods in Healthy Males

Testosterone has been linked to social status seeking in humans. The present study investigated the effects of testosterone administration on implicit and explicit preferences for status goods in healthy male participants (n = 64), using a double-blind, placebo-controlled, between-subjects design. We also investigated the interactive effect between second-to-fourth digit ratio (2D:4D; i.e., a proximal index of prenatal testosterone) and testosterone treatment on status preferences. Results showed that testosterone administration has no discernable influence on self-reported willingness-to-pay (i.e., the explicit measure) or implicit attitudes towards status goods. Individuals with lower 2D:4D (i.e., more masculine) had more positive attitudes for high-status goods on an Implicit Association Task, and this association was abolished with testosterone administration. These data suggest interactive effects of acute testosterone administration and prenatal testosterone exposure on human social status seeking, and highlight the utility of implicit methods for measuring status-related behavior.

The role of social status and testosterone in human conspicuous consumption

Conspicuous consumption refers to the phenomenon where individuals purchase goods for signalling social status, rather than for its inherent functional value. This study (n = 166 male participants) investigated how the outcome of a social competition influenced conspicuous consumption, and its association with competition-induced testosterone reactivity. Winning a competition increased both explicit and implicit preferences for higher-status vs. lower-status products, using both natural stimuli (prestigious cars) and laboratory-tagged stimuli of matched value (university T-shirts). Competition also influenced behaviour in an Ultimatum Game, such that winners were more likely to reject unfair offers. Competition outcomes had no discernible influence upon salivary testosterone levels, and neither basal testosterone levels nor testosterone reactivity induced by competition predicted the conspicuous consumption measures. Our data indicate that winning a competition lead to more dominant behaviour, albeit in a manner that is not statistically regulated by testosterone, possibly through increased feeling of entitlement.

Single-Dose Testosterone Administration Impairs Cognitive Reflection in Men

In nonhumans, the sex steroid testosterone regulates reproductive behaviors such as fighting between males and mating. In humans, correlational studies have linked testosterone with aggression and disorders associated with poor impulse control, but the neuropsychological processes at work are poorly understood. Building on a dual-process framework, we propose a mechanism underlying testosterone’s behavioral effects in humans: reduction in cognitive reflection. In the largest study of behavioral effects of testosterone administration to date, 243 men received either testosterone or placebo and took the Cognitive Reflection Test (CRT), which estimates the capacity to override incorrect intuitive judgments with deliberate correct responses. Testosterone administration reduced CRT scores. The effect remained after we controlled for age, mood, math skills, whether participants believed they had received the placebo or testosterone, and the effects of 14 additional hormones, and it held for each of the CRT questions in isolation. Our findings suggest a mechanism underlying testosterone’s diverse effects on humans’ judgments and decision making and provide novel, clear, and testable predictions.

Testosterone promotes either dominance or submissiveness in the Ultimatum Game depending on players' social rank

Endogenous testosterone promotes behaviours intended to enhance social dominance. However, recent research suggests that testosterone enhances strategic social behaviour rather than dominance seeking behaviour. This possibility has not been tested in a population whose members are known to vary in social status. Here, we explored the relationship between pre-existing social status and salivary testosterone level among members of a rugby team at a Japanese university, where a strong seniority norm maintains hierarchical relationships. Participants played a series of one-shot Ultimatum Games (UG) both as proposer and responder. Opponents were anonymised but of known seniority. We analysed participants' acquiescence (how much more they offered beyond the lowest offer they would accept). The results showed that, among the most senior participants, higher testosterone was associated with lower acquiescence. Conversely, higher testosterone among the lower-status participants was associated with higher acquiescence. Our results suggest that testosterone may enhance socially dominant behaviour among high-status persons, but strategic submission to seniority among lower-status persons.

The Point Subtraction Aggression Paradigm as a laboratory tool for investigating the neuroendocrinology of aggression and competition

A contribution to a special issue on Hormones and Human Competition.The ease of measuring steroids in saliva has led to an increase in investigating their role in competition and aggression in laboratory settings and using behavioral measures of aggression. We review here the Point-Subtraction-Aggression-Paradigm (PSAP) as a measure of costly aggression and we compare and contrast the PSAP to other aggression measures. We describe our use of the PSAP, highlighting how it can be modified to investigate a broad array of experimental questions. We review studies that have investigated neuroendocrine function and the PSAP, and we conclude that across studies the relationship between fluctuations in testosterone and PSAP aggression scores are directionally positive, and are likely specific to men. Investigations of other neuroendocrine measures and the PSAP are fewer, limiting conclusions that can be drawn for other hormones. We provide two versions of the PSAP that can be used with E-PRIME® software for researchers interested in this measure for their laboratories.

Testosterone and androgen receptor gene polymorphism are associated with confidence and competitiveness in men

A contribution to a special issue on Hormones and Human Competition. Studies in non-human animals and humans have demonstrated the important role of testosterone in competitive interactions. Here, we investigated whether endogenous testosterone levels predict the decision to compete, in a design excluding spite as a motive underlying competitiveness. In a laboratory experiment with real monetary incentives, 181 men solved arithmetic problems, first under a noncompetitive piece rate, followed by a competition incentive scheme. We also assessed several parameters relevant to competition, such as risk taking, performance, and confidence in one's own performance. Salivary testosterone levels were measured before and 20min after the competition task using mass spectrometry. Participants were also genotyped for the CAG repeat polymorphism of the androgen receptor gene, known to influence the efficacy of testosterone signaling in a reciprocal relationship to the number of CAG repeats. We observed a significant positive association between basal testosterone levels and the decision to compete, and that higher testosterone levels were related to greater confidence in one's own performance. Whereas the number of CAG repeats was not associated with the choice to compete, a lower number of CAG repeats was related to greater confidence in those who chose to compete, but this effect was attributable to the polymorphism's effect on actual performance. An increase in testosterone levels was observed following the experiment, and this increase varied with self-reported high-school math grades. We expand upon the latest research by documenting effects of the androgen system in confidence in one's own ability, and conclude that testosterone promotes competitiveness without spite.