The endocrine effects of visual erotic stimuli in normal men

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.

Sexual incentive motivation, sexual behavior, and general arousal: Do rats and humans tell the same story?

Sexual incentive stimuli activate sexual motivation and heighten the level of general arousal. The sexual motive may induce the individual to approach the incentive, and eventually to initiate sexual acts. Both approach and the ensuing copulatory interaction further enhance general arousal. We present data from rodents and humans in support of these assertions. We then suggest that orgasm is experienced when the combined level of excitation surpasses a threshold. In order to analyze the neurobiological bases of sexual motivation, we employ the concept of a central motive state. We then discuss the mechanisms involved in the long- and short-term control of that state as well as those mediating the momentaneous actions of sexual incentive stimuli. This leads to an analysis of the neurobiology behind the interindividual differences in responsivity of the sexual central motive state. Knowledge is still fragmentary, and many contradictory observations have been made. Nevertheless, we conclude that the basic mechanisms of sexual motivation and the role of general arousal are similar in rodents and humans.

Functional significance of men's testosterone reactivity to social stimuli

Rapid testosterone fluctuations in response to social stimuli are observed across a wide range of species, and the highly conserved nature of these fluctuations suggests an adaptive function. This paper reviews the current literature on testosterone reactivity, primarily in human males, and illustrates how life-history theory provides an adequate theoretical framework to interpret findings. The review is structured around supporting evidence suggesting that situations implicated in mating effort either directly (e.g., interactions with a mate) or indirectly (e.g., intrasexual competition) are generally associated with a brief elevation of testosterone, while situations implicated in parenting effort (e.g., nurturant interactions with offspring) are generally associated with a decline in testosterone. Further, we discuss how these fluctuations in testosterone have been linked to future behaviors, and how situational, motivational, and physiological variables moderate the interplay between social stimuli, testosterone reactivity, and behavior. Supporting the notion that testosterone can play a causal role in modulating behavior in response to social stimuli, we also summarize recent single administration studies examining the effects of testosterone on physiology, neurobiology, and behavior. A conceptual model provides links between supported findings, and hypothesized pathways requiring future testing.

Placebo and Nocebo Effects in Sexual Medicine: An Experimental Approach

Few studies have investigated placebo and nocebo effects in a human sexuality context. Studying placebo and nocebo responses in this context may provide insight into their potential to modulate sexual drive and function. To examine such effects in sexual medicine, 48 healthy, male heterosexual participants were divided into four groups. Each group received instruction to expect stimulating effects, no effect, or an inhibitory effect on sexual functions. Only one group received the dopamine agonist cabergoline; all other groups received placebo or nocebo. Modulations in sexual experience were examined through an established experimental paradigm of sexual arousal and masturbation-induced orgasm during erotic film sequences with instruction to induce placebo or nocebo effects. Endocrine data, appetitive, consummatory, and refractory sexual behavior parameters were assessed using the Arizona Sexual Experience Scale (ASEX) and the Acute Sexual Experience Scale (ASES). Results showed increased levels of sexual function after administration of cabergoline with significant effects for several parameters. Placebo effects were induced only to a small degree. No negative effects on sexual parameters in the nocebo condition were noted. This paradigm could induce only small placebo and nocebo effects. This supports the view that healthy male sexual function seems relatively resistant to negative external influences.

Interest in Babies Negatively Predicts Testosterone Responses to Sexual Visual Stimuli Among Heterosexual Young Men

Men's testosterone may be an important physiological mechanism mediating motivational and behavioral aspects of the mating/parenting trade-off not only over time but also in terms of stable differences between mating-oriented and parenting-oriented individuals. In this study, we tested the hypothesis that self-reported interest in babies is inversely related to testosterone reactivity to cues of short-term mating among heterosexual young men. Among 100 participants, interest in babies was related to a slow life-history strategy, as assessed by the Mini-K questionnaire, and negatively related to testosterone responses to an erotic video. Interest in babies was not associated with baseline testosterone levels or with testosterone reactivity to nonsexual social stimuli. These results provide the first evidence that differential testosterone reactivity to sexual stimuli may be an important aspect of individual differences in life-history strategies among human males.

Normal male sexual function: emphasis on orgasm and ejaculation

Orgasm and ejaculation are two separate physiological processes that are sometimes difficult to distinguish. Orgasm is an intense transient peak sensation of intense pleasure creating an altered state of consciousness associated with reported physical changes. Antegrade ejaculation is a complex physiological process that is composed of two phases (emission and expulsion), and is influenced by intricate neurological and hormonal pathways. Despite the many published research projects dealing with the physiology of orgasm and ejaculation, much about this topic is still unknown. Ejaculatory dysfunction is a common disorder, and currently has no definitive cure. Understanding the complex physiology of orgasm and ejaculation allows the development of therapeutic targets for ejaculatory dysfunction. In this article, we summarize the current literature on the physiology of orgasm and ejaculation, starting with a brief description of the anatomy of sex organs and the physiology of erection. Then, we describe the physiology of orgasm and ejaculation detailing the neuronal, neurochemical, and hormonal control of the ejaculation process.

Risks and benefits of testosterone therapy in older men

In young men (defined as age<50 years) with classic hypogonadism caused by known diseases of the hypothalamus, pituitary or testes, testosterone replacement therapy induces a number of beneficial effects, for example, the development of secondary sex characteristics, improvement and maintenance of sexual function, and increases in skeletal muscle mass and BMD. Moreover, testosterone treatment in this patient population is associated with a low frequency of adverse events. Circulating testosterone levels decline progressively with age, starting in the second and third decade of life, owing to defects at all levels of the hypothalamic-pituitary-testicular axis. In cohort studies, testosterone levels are associated weakly but consistently with muscle mass, strength, physical function, anaemia, BMD and bone quality, visceral adiposity, and with the risk of diabetes mellitus, coronary artery disease, falls, fractures and mortality. However, the clinical benefits and long-term risks of testosterone therapy--especially prostate-related and cardiovascular-related adverse events--have not been adequately assessed in large, randomized clinical trials involving older men (defined as age>65 years) with androgen deficiency. Therefore, a general policy of testosterone replacement in all older men with age-related decline in testosterone levels is not justified.

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.

Growth hormone, prolactin, and sexuality

GH and PRL, although not considered as 'classi cal' sexual hormones, could play a role in the endocrine control of sexual function both in men and women. Physiologically, PRL seems to be involved in the central control of sexual behavior and activity, by modulating mainly the effects of dopaminergic and serotoninergic systems on sexual function. Indeed, circulating PRL levels increase after orgasm and may potentially play a role in the acute regulation of further sexual arousal following orgasm both in men and women. On the other hand, either short-term or long-term PRL in crease can modulate central nervous system areas involved in the control of sexual function and, peripherally, can directly influence mechanisms of penile erection in men, and presently only as an hypothesis, mechanisms related to the sexual response of genitalia in women. Furthermore, chronic hyperprolactinemia is classically associated with hypogonadotropic hypogonadism and sexual dysfunction in both sexes. Successful treatment of chronic hyperprolactinemia generally restores normal sexual function both in men and women although this effect is not only related to relapse of gonadal function. Hypoprolactinemia is recently recognised as a possible risk factor of arteriogenic erectile dysfunction while a possible role on female sexual function is not known. The physiological role of GH on sexual function is not fully elucidated. GH is an important regulator of hypothalamus-pituitary-gonadal axis and seems to participate in the regulation of the sexual response of genitalia in men, and potentially also in women. Sexual function in men and women with GH deficiency (GHD) and GH excess, particularly in acromegaly, is scantily studied and GH- or IGF-I-dependent effects are difficult to quantify. Nevertheless, a decrease of desire and arousability both in men and women, together with an impairment of erectile function in men, have been described both in patients with GHD and acromegaly, although it is not clear whether they are dependent directly on the hormone defect or excess or they are consequence of the hypogonadism or the different clinical complications or the physical disfigurement and psychological imbalance, which are associated with the diseases, and are potentially affecting sexual function. Data on beneficial effects of GH replacement therapy and specific surgical or pharmacological approach for acromegaly are far to be fully elucidated although restoring normal GH/IGF-I levels have been associated to improvement of sexual function.

The hormonal control of ejaculation

Hormones regulate all aspects of male reproduction, from sperm production to sexual drive. Although emerging evidence from animal models and small clinical studies in humans clearly point to a role for several hormones in controlling the ejaculatory process, the exact endocrine mechanisms are unclear. Evidence shows that oxytocin is actively involved in regulating orgasm and ejaculation via peripheral, central and spinal mechanisms. Associations between delayed and premature ejaculation with hypothyroidism and hyperthyroidism, respectively, have also been extensively documented. Some models suggest that glucocorticoids are involved in the regulation of the ejaculatory reflex, but corresponding data from human studies are scant. Oestrogens regulate epididymal motility, whereas testosterone can affect the central and peripheral aspects of the ejaculatory process. Overall, the data of the endocrine system in regulating the ejaculatory reflex suggest that widely available endocrine therapies might be effective in treating sexual disorders in these men. Indeed, substantial evidence has documented that treatments of thyroid diseases are able to improve some ejaculatory difficulties.

On the intricate relationship between sexual motivation and arousal

Sexual motivation and sexual arousal are widely used concepts. While there seem to be considerable agreement as to the meaning of sexual motivation, there is certain confusion about the exact meaning of sexual arousal. Some use it as a synonym to sexual motivation and others make it equivalent to erection or vaginal lubrication. An unresolved question is the relationship between sexual arousal and general arousal as well as that between arousal and motivation. I present arguments for the view that arousal refers to the general state of alertness of the organism. Consequently, there is no such thing as a specific sexual arousal. I suggest that this term should be abandoned, or if that is not feasible, to make it a synonym to enhanced genital blood flow. The notion of a subjective sexual arousal, some kind of vaguely described mental state, seems to lack all explanatory value. I then show that general arousal is an important determinant of sexual motivation, and that the execution of copulatory acts leads to increased general arousal. This increase leads to enhanced sexual motivation, making the activation of sexual reflexes requiring high levels of motivation possible. Examples of such reflexes may be ejaculation in males of many species, and perhaps the psychic state of orgasm in women.

Contact with attractive women affects the release of cortisol in men

Previous studies have shown that situations relevant for human mating can affect the levels of many hormones. This study focused on the hypothalamus-pituitary-adrenal axis by measuring salivary cortisol levels in 84 young men prior to and after a period of short social contact with a woman or man. Results showed that after contact with another man the cortisol levels of the participants declined according to the circadian release pattern of cortisol. However, cortisol levels in men declined less when they had contact with a woman. Furthermore, cortisol levels of men increased when they perceived the woman with whom they had contact as attractive. Our findings provide indirect evidence for the role of the hypothalamus-pituitary-adrenal axis in human courtship. During social contact with attractive women, moderate increases in cortisol levels may reflect apprehension over an opportunity for courtship.

Relationship between testosterone and interest in sexual stimuli: the effect of experience

Testosterone is commonly thought to drive male sexual interest, but little experimental evidence demonstrates a direct relationship between natural variation in testosterone and sexual interest in healthy young men. This study measured young men's testosterone levels and their interest in visual sexual stimuli across three test sessions within 1 month. Fifteen men aged 23-28 viewed pictures of couples engaged in sexually explicit activity. Each session included a unique set of 72 pictures depicting heterosexual oral sex or intercourse presented in randomized order. Participants controlled how long they viewed each picture, with viewing time indicating sexual interest. Men's testosterone (T) levels were assayed from blood spots obtained prior to viewing the pictures. Overall, T and viewing time were positively correlated; however, the strength of this relationship varied by test session. T was marginally correlated with viewing time during the first session (r=0.43) and not significantly correlated with viewing time on the second session (r=0.16). During the final test session, when habituation might influence male interest in the stimuli, T was strongly correlated with viewing time (r=0.80). Thus, the current study demonstrates a direct but context dependent relationship between testosterone and sexual interest in healthy young males.

Rapid endocrine responses of young men to social interactions with young women

It is well-established that males of many nonhuman vertebrate species exhibit hormonal reactions to stimuli from potential mates. The present studies were designed to test replication of preliminary findings suggesting that human males may exhibit such reactions as well. In Experiment 1, young men (n=115) provided saliva samples before and after either conversing with a woman confederate or sitting alone for 15 min. Changes from baseline in salivary testosterone concentrations were significantly greater among the men exposed to women, but only among subjects tested in the afternoon. In Experiment 2, male subjects (n=99) interacted with either a male or a female confederate with saliva samples collected before and after these interactions and all experimental sessions conducted in the afternoon. Men who interacted with women exhibited significant elevations of testosterone relative to both their own baseline concentrations and to change scores among the men who interacted with other men. In addition, women confederates' ratings of men's extraversion and degree of self-disclosure were positively correlated with changes in testosterone. In both experiments, furthermore, changes in cortisol concentrations from baseline were significantly greater among men who spoke with women relative to men in the control conditions. The results provide evidence that social interactions with potential mates can in fact trigger specific patterns of endocrine responses in human males.

Associations between testosterone secretion and sexual activity in women

Some studies show an increase in testosterone (T) after sexual activity; this literature has inconsistent findings, focuses mostly on men, and does not employ control activities. The present study examined within-subject effects of intercourse versus control activities (cuddling; exercise) on salivary T. The initial sample included 49 women (mostly heterosexual), though not all participants returned all samples or engaged in all activities, leaving a smaller sample for endocrine analyses (n=16). Participants attended an initial session in the laboratory where they completed questionnaires, and then engaged in the activities on their own. On three separate nights, they provided pre-activity, post-activity, and next-morning saliva samples and completed brief questionnaires at the last two timepoints. Women's T was higher pre-intercourse than pre-control activity. Women's T was also higher post-intercourse than post-control activity, though the percent change in T from pre- to post-activity was highest for cuddling, then intercourse, then exercise. Next-morning T did not differ by activity. Data pointed to an association between T and orgasming, sexual desire, and relationship commitment. Analyses on post-activity appraisals suggest that the close intimate physicality of a sexual and non-sexual nature can affect T and be beneficial in short-term and perhaps longer-lasting ways for women's sexuality and relationships.

Neuroendocrine response to female ovulatory odors depends upon social condition in male common marmosets, Callithrix jacchus

Male mammals show rapid behavioral and hormonal responses to signals from sexually receptive females. However, rapid endocrine responses to female signals have not been observed in a nonhuman primate. Here, we tested the behavioral and hormonal response of male common marmosets (Callithrix jacchus) to isolated scent secretions from ovulatory females or to vehicle control scent. Fifteen males were tested in their home cage for behavioral and hormonal responses. These males showed increased investigative and arousal behaviors to the ovulatory scent compared to the vehicle scent. Time sniffing the scent substrate and the duration of erections were significantly elevated in relation to the vehicle scent. Thirty minutes after presentation of ovulatory scent, males showed a significant increase in testosterone compared to the vehicle, but there was no difference in cortisol values. To better control for scent presentation, 15 additional males were tested under a controlled scent exposure. Current social housing condition influenced the male's testosterone response to the ovulatory scent. Single and paired males showed significant increases in testosterone levels with the ovulatory scent but did not increase cortisol levels. Single males also showed the highest change in testosterone with the ovulatory scent, but fathers showed no changes. These results indicate that a rapid hormonal response to sexually arousing cues occurs in marmosets, and the data suggest that a male's social condition influences how he responds to sexually relevant cues.

Emotional perception and neuroendocrine changes

The present study was designed to investigate the neuroendocrine modifications during affective states. In particular, we investigate if the pleasantness of the stimuli has a different effect on neuroendocrine responses. To address this issue, we compared the effects of pleasant, neutral, and unpleasant pictures on catecholamine, adrenocorticotrophic hormone (ACTH), cortisol, and prolactin plasma levels. Ten male participants were submitted to three experimental sessions, each on one of the three experimental days, a week apart in a counterbalanced order. Although in the subjective arousal rating, pleasant (erotic pictures) and unpleasant stimuli (pictures of mutilated bodies) receive the same high score, a different neuroendocrine pattern was obtained: unpleasant stimuli elicited a decrease in prolactin concentration and increases in noradrenaline, cortisol, and ACTH levels, whereas pleasant slide set viewing induced an increase in prolactin levels. The results suggest that the neuroendocrine system responds selectively to affective motivationally relevant pictures.

Neuroendocrine response to film-induced sexual arousal in men and women

The psychoneuroendocrine responses to sexual arousal have not been clearly established in humans. However, we have demonstrated previously that masturbation-induced orgasm stimulates cardiovascular activity and induces increases in catecholamines and prolactin in blood of both males and females. We presently investigated the role of orgasm in producing these effects. Therefore, in this study parallel analysis of prolactin, adrenaline, noradrenaline, and cortisol concentrations, together with cardiovascular variables of systolic/diastolic blood pressure and heart rate were undertaken during film-induced sexual arousal in nine healthy adult men and nine healthy adult women. Blood was drawn continuously via an indwelling cannula and connected tubing system passed through a mini-pump. In parallel, the cardiovascular parameters were recorded continuously via a computerised finger-cuff sensor. Subjective sexual arousal increased significantly in both men and women during the erotic film, with sexual arousal eliciting an increase in blood pressure in both males and females, and plasma noradrenaline in females only. In contrast, adrenaline, cortisol and prolactin levels were unaffected by sexual arousal. These data further consolidate the role of sympathetic activation in sexual arousal processes. Furthermore, they demonstrate that increases in plasma prolactin during sexual stimulation are orgasm-dependent, suggesting that prolactin may regulate a negative-feedback sexual-satiation mechanism.

Cardiovascular and endocrine alterations after masturbation-induced orgasm in women

OBJECTIVE

The present study investigated the cardiovascular, genital, and endocrine changes in women after masturbation-induced orgasm because the neuroendocrine response to sexual arousal in humans is equivocal.

METHODS

Healthy women (N = 10) completed an experimental session, in which a documentary film was observed for 20 minutes, followed by a pornographic film for 20 minutes, and another documentary for an additional 20 minutes. Subjects also participated in a control session, in which participants watched a documentary film for 60 minutes. After subjects had watched the pornographic film for 10 minutes in the experimental session, they were asked to masturbate until orgasm. Cardiovascular (heart rate and blood pressure) and genital (vaginal pulse amplitude) parameters were monitored continuously throughout testing. Furthermore, blood was drawn continuously for analysis of plasma concentrations of adrenaline, noradrenaline, cortisol, prolactin, luteinizing hormone (LH), beta-endorphin, follicle-stimulating hormone (FSH), testosterone, progesterone, and estradiol.

RESULTS

Orgasm induced elevations in cardiovascular parameters and levels of plasma adrenaline and noradrenaline. Plasma prolactin substantially increased after orgasm, remained elevated over the remainder of the session, and was still raised 60 minutes after sexual arousal. In addition, sexual arousal also produced small increases in plasma LH and testosterone concentrations. In contrast, plasma concentrations of cortisol, FSH, beta-endorphin, progesterone, and estradiol were unaffected by orgasm.

CONCLUSIONS

Sexual arousal and orgasm produce a distinct pattern of neuroendocrine alterations in women, primarily inducing a long-lasting elevation in plasma prolactin concentrations. These results concur with those observed in men, suggesting that prolactin is an endocrine marker of sexual arousal and orgasm.

Neuroendocrine and cardiovascular response to sexual arousal and orgasm in men

Data regarding the neuroendocrine response pattern to sexual arousal and orgasm in man are inconsistent. In this study, ten healthy male volunteers were continuously monitored for their cardiovascular and neuroendocrine response to sexual arousal and orgasm. Blood was continuously drawn before, during and after masturbation-induced orgasm and analyzed for plasma concentrations of adrenaline, noradrenaline, cortisol, luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin, growth hormone (GH), beta-endorphin and testosterone. Orgasm induced transient increases in heart rate, blood pressure and noradrenaline plasma levels. Prolactin plasma levels increased during orgasm and remained elevated 30 min after orgasm. In contrast, none of the other endocrine variables were significantly affected by sexual arousal and orgasm.

Sexual rehabilitation after treatment for prostate cancer

Although there is little evidence that sexual behavior causes prostate cancer, men with prostate cancer often have sexual dysfunction before the cancer diagnosis is made. Each treatment for prostate cancer increases the prevalence of sexual problems. After nerve-sparing radical prostatectomy, the chance of recovering erections is better for men who are younger and in whom both neurovascular bundles can be spared. Definitions of "potency" after nerve-sparing surgery have not specified the rigidity of the erections achieved. Thus, some men classified as "potent" may wish additional sexual rehabilitation. The chance that definitive radiation therapy will cause erectile dysfunction probably has been overestimated. The prevalence rate may be closer to 25% of men with new problems compared with the 50% often cited in the literature. Men are more at risk to have erection problems after radiation therapy if the quality of erections before treatment was borderline. Hormonal therapy has an impact on the central mechanisms mediating sexual desire and arousability. Therefore, with most treatment methods, only approximately 20% of men remain sexually functional. Newer antiandrogenic drugs interfere less with sexual function, but their long-term ability to control prostate cancer is still under investigation. Sexual rehabilitation should be addressed by the primary care team. Sexual partners should be included in brief sexual counseling, even when a mechanical treatment for erectile dysfunction is prescribed.

LH pulsatile secretion and testosterone blood levels are influenced by sexual arousal in human males

To determine whether changes in LH and testosterone (T) blood levels and pulse signals were induced by sexual arousal, nine healthy young males were presented on two different days with a sexually arousing (S) and a sexually neutral control (C) film. On both sessions, blood was sampled every 10 min for 12 hr. The Cluster and the Detect pulse identification algorithms were used to characterize the peaks in LH and T series. The second plasma LH peak following the beginning of the film was higher in the S than in the C condition (percent increases above preceding nadir: 322.1 +/- 183.9% vs. 202.6 +/- 108.7%). The area of the second pituitary peak of LH instantaneous secretion rate, which corresponded to the second plasma LH peak, was also greater in the S condition (6.2 +/- 3.3 vs. 3.4 +/- 2.3 UI/l). Compared with the C condition, T blood levels were increased within the first 10 min of sexual arousal (25.2 +/- 6.3 vs. 22.2 +/- 5.6 nmol/l). These results, consistent with the findings of animal studies, indicate that LH pulsatile secretion and T blood levels are influenced by changes in the state of sexual arousal in human males.