Coitus-induced orgasm stimulates prolactin secretion in healthy subjects

Low prolactin level identifies hypoactive sexual desire disorder women with a reduced inhibition profile

PURPOSE

Data on the role of prolactin (PRL) in the physiologic range in the female sexual response are scanty. We aimed at investigating the association between PRL and sexual function as assessed by the Female Sexual Function Index (FSFI). We explored the presence of a cut-off level of PRL able to identify Hypoactive Sexual Desire Disorder (HSDD).

METHODS

277 pre- and post-menopausal women consulting for Female Sexual Dysfunction (FSD) and sexually active were enrolled in an observational, retrospective study. 42 women were used as no-FSD controls. A clinical, biochemical and psychosexual evaluation was performed. The main outcome measures were: FSFI, Female Sexual Distress Scale-Revised, Middlesex Hospital Questionnaire and Sexual excitation/sexual inhibition scale (SIS/SES).

RESULTS

Normo-PRL FSD women (n = 264) showed lower FSFI Desire score than controls (n = 42), and higher than hyper-PRL FSD women (n = 13). These differences emerged both in pre-menopausal and post-menopausal subjects. In the normo-PRL FSD group, those with PRL in the higher quintile reported higher FSFI Desire scores than those with PRL in the lowest quintile. Women with HSDD presented a lower PRL level than those without (p = 0.032). A ROC curve analysis for PRL showed an accuracy of 0.610 ± 0.044 (p = 0.014) in predicting HSDD. With a threshold of < 9.83 μg/L, sensitivity and specificity for HSDD were 63% and 56%, respectively. Subjects with PRL < 9.83 μg/L also reported lower sexual inhibition (p = 0.006) and lower cortisol levels (p = 0.003) than those with PRL >  = 9.83 μg/L.

CONCLUSIONS

Hyper-PRL is associated with low desire; however, among normo-PRL FSD women, those with the lowest levels demonstrated a poorer desire than those with the highest levels. PRL < 9.83 μg/L predicted HSDD and a lower sexual inhibitory trait.

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.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

The effect of baculum shape and mating behavior on mating-induced prolactin release in female house mice

Male genitalia are subject to rapid divergent evolution, and sexual selection is believed to be responsible for this pattern of evolutionary divergence. Genital stimulation during copulation is an essential feature of sexual reproduction. In mammals, the male intromittent genitalia induces a cascade of physiological and neurological changes in females that promote pregnancy. Previous studies of the house mouse have shown that the shape of the baculum (penis bone) influences male reproductive success and responds to experimentally imposed variation in sexual selection. Here, we test the hypothesis that the baculum is subject to sexual selection due to a stimulatory function during copulation. We selected male and female house mice (Mus musculus domesticus) from families with breeding values at the extremes of baculum shape and performed two series of experimental matings following which we examined the concentration of prolactin in the blood of females either 15 (“early”) or 75 (“late”) min after ejaculation. Our results provide evidence of a mating-induced release of prolactin in the female house mouse early after ejaculation, the level of which is dependent on an interaction between the shape of the baculum and male sexual behavior. Our data thereby provide novel insight into the mechanism(s) of sexual selection acting on the mammalian baculum.

No evidence for prolactin's involvement in the post-ejaculatory refractory period

In many species, ejaculation is followed by a state of decreased sexual activity, the post-ejaculatory refractory period. Several lines of evidence have suggested prolactin, a pituitary hormone released around the time of ejaculation in humans and other animals, to be a decisive player in the establishment of the refractory period. However, data supporting this hypothesis is controversial. We took advantage of two different strains of house mouse, a wild derived and a classical laboratory strain that differ substantially in their sexual performance, to investigate prolactin's involvement in sexual activity and the refractory period. First, we show that there is prolactin release during sexual behavior in male mice. Second, using a pharmacological approach, we show that acute manipulations of prolactin levels, either mimicking the natural release during sexual behavior or inhibiting its occurrence, do not affect sexual activity or shorten the refractory period, respectively. Therefore, we show compelling evidence refuting the idea that prolactin released during copulation is involved in the establishment of the refractory period, a long-standing hypothesis in the field of behavioral endocrinology.

Secretion and Function of Pituitary Prolactin in Evolutionary Perspective

The hypothalamo-pituitary system developed in early vertebrates. Prolactin is an ancient vertebrate hormone released from the pituitary that exerts particularly diverse functions. The purpose of the review is to take a comparative approach in the description of prolactin, its secretion from pituitary lactotrophs, and hormonal functions. Since the reproductive and osmoregulatory roles of prolactin are best established in a variety of species, these functions are the primary subjects of discussion. Different types of prolactin and prolactin receptors developed during vertebrate evolution, which will be described in this review. The signal transduction of prolactin receptors is well conserved among vertebrates enabling us to describe the whole subphylum. Then, the review focuses on the regulation of prolactin release in mammals as we have the most knowledge on this class of vertebrates. Prolactin secretion in response to different reproductive stimuli, such as estrogen-induced release, mating, pregnancy and suckling is detailed. Reproduction in birds is different from that in mammals in several aspects. Prolactin is released during incubation in avian species whose regulation and functional significance are discussed. Little information is available on prolactin in reptiles and amphibians; therefore, they are mentioned only in specific cases to explain certain evolutionary aspects. In turn, the osmoregulatory function of prolactin is well established in fish. The different types of pituitary prolactin in fish play particularly important roles in the adaptation of eutherian species to fresh water environments. To achieve this function, prolactin is released from lactotrophs in hyposmolarity, as they are directly osmosensitive in fish. In turn, the released prolactin acts on branchial epithelia, especially ionocytes of the gill to retain salt and excrete water. This review will highlight the points where comparative data give new ideas or suggest new approaches for investigation in other taxa.

Patterns of prolactin secretion

Prolactin is pleotropic in nature affecting multiple tissues throughout the body. As a consequence of the broad range of functions, regulation of anterior pituitary prolactin secretion is complex and atypical as compared to other pituitary hormones. Many studies have provided insight into the complex hypothalamic-pituitary networks controlling prolactin secretion patterns in different species using a range of techniques. Here, we review prolactin secretion in both males and females; and consider the different patterns of prolactin secretion across the reproductive cycle in representative female mammals with short versus long luteal phases and in seasonal breeders. Additionally, we highlight changes in the pattern of secretion during pregnancy and lactation, and discuss the wide range of adaptive functions that prolactin may have in these important physiological states.

Sexual Behavior and Synaptic Plasticity

Although sex drive is present in many animal species, sexual behavior is not static and, like many other behaviors, can be modified by experience. This modification relies on synaptic plasticity, a sophisticated mechanism through which neurons change how they process a given stimulus, and the neurophysiological basis of learning. This review addresses the main plastic effects of steroid sex hormones in the central nervous system (CNS) and the effects of sexual experience on the CNS, including effects on neurogenesis, intracellular signaling, gene expression, and changes in dendritic spines, as well as behavioral changes.

Sexually dimorphic neuronal inputs to the neuroendocrine dopaminergic system governing prolactin release

Prolactin (PRL) is a pleiotropic hormone that was identified in the context of maternal care and its release from the anterior pituitary is primarily controlled by neuroendocrine dopaminergic (NEDA) neurones of the arcuate nucleus of the hypothalamus. The sexually dimorphic nature of PRL physiology and associated behaviours is evident in mammals, even though the number and density of NEDA neurones is reported as not being sexually dimorphic in rats. However, the underlying circuits controlling NEDA neuronal activity and subsequent PRL release are largely uncharacterised. Thus, we mapped whole-brain monosynaptic NEDA inputs in male and female mice. Accordingly, we employed a rabies virus based monosynaptic tracing system capable of retrogradely mapping inputs into genetically defined neuronal populations. To gain genetic access to NEDA neurones, we used the dopamine transporter promoter. Here, we unravel 59 brain regions that synapse onto NEDA neurones and reveal that male and female mice, despite monomorphic distribution of NEDA neurones in the arcuate nucleus of the hypothalamus, receive sexually dimorphic amount of inputs from the anterior hypothalamic nucleus, anteroventral periventricular nucleus, medial preoptic nucleus, paraventricular hypothalamic nucleus, posterior periventricular nucleus, supraoptic nucleus, suprachiasmatic nucleus, lateral supramammillary nucleus, tuberal nucleus and periaqueductal grey. Beyond highlighting the importance of considering sex as a biological variable when evaluating connectivity in the brain, these results illustrate a case where a neuronal population with similar anatomical distribution has a subjacent sexually dimorphic connectivity pattern, potentially capable of contributing to the sexually dimorphic nature of PRL release and function.

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.

Social behavior, hormones and adult neurogenesis

A variety of experiences have been shown to affect the production of neurons in the adult hippocampus. These effects may be mediated by experience-driven hormonal changes, which, in turn, interact with factors such as sex, age and life history to alter brain plasticity. Although the effects of physical experience and stress have been extensively characterized, various types of social experience across the lifespan trigger profound neuroendocrine changes in parallel with changes in adult neurogenesis. This review article focuses on the influence of specific social experiences on adult neurogenesis in the dentate gyrus and the potential role of hormones in these effects.

Cabergoline in the Treatment of Male Orgasmic Disorder-A Retrospective Pilot Analysis

Introduction

Male orgasmic disorder is common, with few treatment options. Cabergoline is a dopamine agonist that acts centrally to normalize serum prolactin that could improve orgasmic dysfunction.

Aims

To determine whether cabergoline increases the potential for orgasm in men with orgasmic disorder.

Methods

A retrospective chart review of men treated in a single andrology clinic for delayed orgasm or anorgasmia in a pilot study using cabergoline 0.5 mg twice weekly was performed. Duration of treatment and response were noted. Medical records were examined for other factors including history of prostatectomy and concomitant androgen supplementation.

Main Outcome Measures

Subjective improvement in orgasmic function resulting from cabergoline treatment.

Results

Of 131 men treated with cabergoline for orgasmic disorder, 87 (66.4%) reported subjective improvement in orgasm and 44 (33.6%) reported no change in orgasm. Duration of therapy (P = .03) and concomitant testosterone therapy (P = .02) were associated with a significant positive response to cabergoline treatment. No differences were found between injectable and non-injectable testosterone formulations (P = .90), and neither age (P = .90) nor prior prostatectomy (P = .41) influenced the outcome of cabergoline treatment. Serum testosterone levels before (P = .26) and after (P = .81) treatment were not significantly different in responders vs non-responders.

Conclusion

Cabergoline is a potentially effective and easy-to-administer treatment for male orgasmic disorder, the efficacy of which appears to be independent of patient age or orgasmic disorder etiology. Prospective randomized trials are needed to determine the true role of cabergoline in the treatment of this disorder.

Multiple Orgasms in Men-What We Know So Far

INTRODUCTION

There is much popular discussion on strategies to facilitate multiple orgasms in men (ie, 100,000+ hits in Google), yet the topic has not received an objective comprehensive review in the literature.

AIM

To review the literature on male multiple orgasms.

METHODS

We searched the literature for publications on "male multiple orgasms" and factors influencing male multiple orgasms in Google, PubMed, and PsychINFO. This yielded 15 relevant publications.

MAIN OUTCOME MEASURES

A comprehensive overview on the topic of male multiple orgasms and factors that influence the propensity of men to experience multiple orgasms.

RESULTS

Few men are multiorgasmic: <10% for those in their 20s, and <7% after the age of 30. The literature suggests 2 types of male multiple orgasms: "sporadic" multiorgasms, with interorgasmic intervals of several minutes, and "condensed" multiorgasms, with bursts of 2-4 orgasms within a few seconds to 2 minutes. Multiple orgasms appear physiologically similar to the single orgasm in mono-orgasmic men. However, in a single case study, a multiorgasmic man did not experience with his first orgasm the prolactin surge that usually occurs with orgasm in mono-orgasmic men. Various factors may facilitate multiple orgasms: (1) practicing to have an orgasm without ejaculation; (2) using psychostimulant drugs; (3) having multiple and/or novel sexual partners; or (4) using sex toys to enhance tactile stimulation. However, confirmatory physiological data on any of these factors are few. In some cases, the ability to experience multiple orgasms may increase after medical procedures that reduce ejaculation (eg, prostatectomy or castration), but what factor(s) influence this phenomenon is poorly investigated.

CONCLUSION

Despite popular interest, the topic of male multiple orgasms has received surprisingly little scientific assessment. The role of ejaculation and physiological change during the refractory period in inhibiting multiple orgasms has barely been investigated.

Animal Models for the Study of Female Sexual Dysfunction

INTRODUCTION

Significant progress has been made in elucidating the physiological and pharmacological mechanisms of female sexual function through preclinical animal research. The continued development of animal models is vital for the understanding and treatment of the many diverse disorders that occur in women.

AIM

To provide an updated review of the experimental models evaluating female sexual function that may be useful for clinical translation.

METHODS

Review of English written, peer-reviewed literature, primarily from 2000 to 2012, that described studies on female sexual behavior related to motivation, arousal, physiological monitoring of genital function and urogenital pain.

MAIN OUTCOMES MEASURES

Analysis of supporting evidence for the suitability of the animal model to provide measurable indices related to desire, arousal, reward, orgasm, and pelvic pain.

RESULTS

The development of female animal models has provided important insights in the peripheral and central processes regulating sexual function. Behavioral models of sexual desire, motivation, and reward are well developed. Central arousal and orgasmic responses are less well understood, compared with the physiological changes associated with genital arousal. Models of nociception are useful for replicating symptoms and identifying the neurobiological pathways involved. While in some cases translation to women correlates with the findings in animals, the requirement of circulating hormones for sexual receptivity in rodents and the multifactorial nature of women's sexual function requires better designed studies and careful analysis. The current models have studied sexual dysfunction or pelvic pain in isolation; combining these aspects would help to elucidate interactions of the pathophysiology of pain and sexual dysfunction.

CONCLUSIONS

Basic research in animals has been vital for understanding the anatomy, neurobiology, and physiological mechanisms underlying sexual function and urogenital pain. These models are important for understanding the etiology of female sexual function and for future development of pharmacological treatments for sexual dysfunctions with or without pain. Marson L, Giamberardino MA, Costantini R, Czakanski P, and Wesselmann U. Animal models for the study of female sexual dysfunction. Sex Med Rev 2013;1:108-122.

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.

Copulation is reactivated by bromocriptine in male rats after reaching sexual satiety with a same sexual mate

Male sexual satiety has been associated with a decrease in dopamine levels. Spontaneous recovery of copulatory behavior begins at least 72 h after sexual satiety is reached or in the condition in which a sexually-satiated male is exposed to a new receptive female distinct from the one with which sexual satiety was reached. The aim of the present study was to explore whether dopaminergic activation by bromocriptine (BrCr) can reactivate copulatory behavior with the same sexual mate immediately after sexual satiety is reached. Male rats were divided into three groups exposed to one of the following three conditions: 1) administration of 2 mg/kgs.c. of BrCr and exposure to the same female with whom sexual satiety was previously reached; 2) administration of 0.3 mLs.c. of the vehicle solution with exposure to the same female with whom sexual satiety was reached; and, 3) exposure to a new receptive female after sexual satiety was reached. Results showed that BrCr significantly reactivated copulatory capability in sexually-satiated males with the same receptive female. In contrast, no males in the vehicle group ejaculated with the same female after reaching sexual exhaustion. Copulation was reactivated by BrCr in a way similar to that observed in untreated males exposed to a new receptive female (i.e., the Coolidge effect). The reversal of sexual satiety in the males treated with BrCr could be explained by its action on D2 family receptors, which promotes a reactivation of sexual motivation at a level sufficient to allow renewed copulation with the same female mate.

Differential effects of intranasal oxytocin on sexual experiences and partner interactions in couples

Knowledge about the effects of the neuropeptide oxytocin (OXT) on human sexual behaviors and partner interactions remains limited. Based on our previous studies, we hypothesize that OXT should be able to positively influence parameters of sexual function and couple interactions. Employing a naturalistic setting involving 29 healthy heterosexual couples (n=58 participants), we analyzed the acute effects of intranasally administered OXT (24IU) on sexual drive, arousal, orgasm and refractory aspects of sexual behavior together with partner interactions. Data were assessed by psychometric instruments (Acute Sexual Experiences Scale, Arizona Sexual Experience Scale) as well as biomarkers, such as cortisol, α-amylase and heart rate. Intranasal OXT administration did not alter "classical" parameters of sexual function, such as sexual drive, arousal or penile erection and lubrication. However, analysis of variance and a hierarchical linear model (HLM) revealed specific effects related to the orgasmic/post-orgasmic interval as well as parameters of partner interactions. According to HLM analysis, OXT increased the intensity of orgasm, contentment after sexual intercourse and the effect of study participation. According to ANOVA analysis, these effects were more pronounced in men. Men additionally indicated higher levels of sexual satiety after sexual intercourse with OXT administration. Women felt more relaxed and subgroups indicated better abilities to share sexual desires or to empathize with their partners. The effect sizes were small to moderate. Biomarkers indicated moderate psychophysiological activation but were not affected by OXT, gender or method of contraception. Using a naturalistic setting, intranasal OXT administration in couples exerted differential effects on parameters of sexual function and partner interactions. These results warrant further investigations, including subjects with sexual and relationship problems.

Female orgasm but not male ejaculation activates the pituitary. A PET-neuro-imaging study

The pituitary gland plays an important role in basic survival mechanisms by releasing fluctuating amounts of hormones into the bloodstream, depending on the circumstances the individual finds itself. However, despite these changes in pituitary hormonal production, neuroimaging studies have never been able to demonstrate changes in the activation level of the pituitary. The most apparent reason is the much higher blood flow rate in the pituitary than in the brain. However, the present PET-scanning study demonstrates for the first time that neuroimaging techniques can identify increased pituitary activity. In a study with 11 healthy women sexual orgasm compared to rest caused an increased blood supply to the pituitary. We assume that this increase signifies elevated pituitary activation in order to produce higher plasma concentrations of oxytocin and prolactin. These hormones induce vaginal and uterus movements, ovulation and enhancement of sperm and egg transport. No increased blood supply was observed comparing clitoral stimulation, orgasm attempt, and faked orgasm with rest. In a study with 11 healthy men comparing ejaculation with rest did not reveal increased pituitary activation, probably because ejaculation causes a much lower increase of oxytocin and prolactin plasma concentration than female orgasm.

Extracellular signal-regulated kinase 5 (ERK5) mediates prolactin-stimulated adult neurogenesis in the subventricular zone and olfactory bulb

Prolactin-stimulated adult neurogenesis in the subventricular zone (SVZ) and olfactory bulb (OB) mediates several reproductive behaviors including mating/pregnancy, dominant male pheromone preference in females, and paternal recognition of offspring. However, downstream signaling mechanisms underlying prolactin-induced adult neurogenesis are completely unknown. We report here for the first time that prolactin activates extracellular signal-regulated kinase 5 (ERK5), a MAP kinase that is specifically expressed in the neurogenic regions of the adult mouse brain. Knockdown of ERK5 by retroviral infection of shRNA attenuates prolactin-stimulated neurogenesis in SVZ-derived adult neural stem/progenitor cells (aNPCs). Inducible erk5 deletion in adult neural stem cells of transgenic mice inhibits neurogenesis in the SVZ and OB following prolactin infusion or mating/pregnancy. These results identify ERK5 as a novel and critical signaling mechanism underlying prolactin-induced adult neurogenesis.

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.

The role of oxytocin in mating and pregnancy

The hormone oxytocin (OT) is released both centrally and peripherally during and after mating. Although research in humans suggests a central role in sexuality, the most reliable findings to date involve peripheral activation. This review will discuss these results and will particularly focus on understanding the most recent findings from fMRI data and the effects of exogenous peripheral OT administration. We will then consider hypotheses of the roles played by central and systemic OT release as well as their control and modulation in the female, summarizing recent findings from animal research. Finally, we will discuss the contribution of OT to the initiation of pregnancy in rodents. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Is there a significance of histamine in the control of the human male sexual response?

Although histamine has been suggested to be involved in the control of male sexual function, including the induction of penile erection, its role in the human corpus cavernosum penis is still poorly understood. The aim of our study was to evaluate the course of histamine plasma levels through different stages of sexual arousal in the systemic and cavernous blood of healthy male subjects. Thirty four (34) healthy men were exposed to erotic stimuli to elicit penile erection. Blood was aspirated from the corpus cavernosum and a cubital vein during the penile conditions flaccidity, tumescence, rigidity and detumescence. Blood was also collected in the post-ejaculatory period. Plasma levels of histamine (ng ml(-1)) were determined by means of a radioimmunoassay. Histamine slightly decreased in the cavernous blood when the penis became tumescent. During rigidity, histamine decreased further but remained unaltered in the phase of detumescence and after ejaculation. In the systemic circulation, no alterations were observed with the initiation or termination of penile erection, whereas a significant drop was registered following ejaculation. Results are not in favour of the hypothesis of an excitatory role of histamine in the control of penile erection. Nevertheless, the amine might mediate biological events during the post-ejaculatory period.

Factors associated with ejaculatory and orgasmic dysfunction in men with erectile dysfunction: analysis of clinical trials involving the phosphodiesterase type 5 inhibitor tadalafil

OBJECTIVE

To determine frequencies of, and risk factors for, ejaculatory dysfunction (EjD) and orgasmic dysfunction (OD) in men with different degrees of erectile dysfunction (ED).

PATIENTS AND METHODS

Baseline data from 28 ED trials were integrated and analysed. The International Index of Erectile Function Question 9 (IIEF-Q9; 'When you had sexual stimulation or intercourse, how often did you ejaculate?') and IIEF-Q10 ('How often did you have the feeling of orgasm with or without ejaculation?') were used to evaluate ejaculatory and orgasmic functions. Responses of 'almost never or never' or 'a few times (much less than half the time)' were taken as evidence of EjD or OD, respectively, whereas responses of 'almost always or always' or 'most times (much more than half the time)' were taken as evidence of normal function. Estimates of the relative risks (RRs) of EjD or OD were determined for multiple patient characteristics.

RESULTS

Among 12,130 study participants with available data, only 5117 (42.2%) reported normal ejaculatory function, and 4321 (35.6%) normal orgasm, regardless of ED severity. Among subjects with poor ejaculatory function, 16.7% had mild ED, and among subjects with poor sensation of orgasm, 21.9% had mild ED. Frequencies of EjD and OD increased with increasing ED severity. Of the 5117 individuals with normal ejaculatory function, 796 (15.6%) had poor sensation of orgasm. Of the 4321 subjects with normal orgasm, 226 (5.2%) had poor ejaculatory function. Men with (vs without) EjD or OD tended to be younger: 53.7 vs 56.9 years and 54.2 vs 56.2 years, respectively. Factors associated with increased RRs of EjD and OD included cardiomyopathy (RR for EjD 1.74; RR for OD 1.59); cardiac failure (RR 1.40; 1.22); and baseline use (or history of use) of antipsychotics (RR 1.45; 1.30), selective serotonin reuptake inhibitors (RR 1.31; 1.27), and tricyclic antidepressants (RR 1.34; 1.28).

CONCLUSIONS

EjD and OD occurred at baseline in more than one in three men enrolled in tadalafil trials. Even men with mild ED reported EjD or OD. Further studies are warranted to better understand the impacts of EjD and OD on male sexuality and quality of life.

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.

In the mood for love or vice versa? Exploring the relations among sexual activity, physical affection, affect, and stress in the daily lives of mid-aged women

How do physical affection, sexual activity, mood, and stress influence one another in the daily lives of mid-aged women? Fifty-eight women (M age, 47.6 yrs) recorded physical affection, several different sexual behaviors, stressful events, and mood ratings every morning for 36 weeks. Using multilevel modeling, we determined that physical affection or sexual behavior with a partner on one day significantly predicted lower negative mood and stress and higher positive mood on the following day. The relation did not hold for orgasm without a partner. Additionally, positive mood on one day predicted more physical affection and sexual activity with a partner, but fewer solo orgasms the following day. Negative mood was mostly unrelated to next-day sexual activity or physical affection. Sexual orientation, living with a partner, and duration of relationship moderated some of these effects. Results support a bidirectional causal model in which dyadic sexual interaction and physical affection improve mood and reduce stress, with improved mood and reduced stress in turn increasing the likelihood of future sex and physical affection.

Serial neurochemical measurement of cerebrospinal fluid during the human sexual response cycle

Recent studies examining the neuroendocrine response pattern underlying the human sexual response cycle revealed transient activation of the sympathoadrenal system and a substantial, long-lasting increase in plasma prolactin concentrations following orgasm in men and women. Prolactin has been discussed as being part of a feedback mechanism that signals centers in the central nervous system, such as the dopaminergic system controlling sexual arousal. To further elucidate the central role of neuropeptides, biogenic monoamines and neurotransmitters in human sexual behavior, a serial cerebrospinal fluid (CSF)-sampling technique was implemented using a previously established experimental paradigm for sexual activity in a laboratory setting. In parallel with peripheral endocrine measures, lumbar CSF was drawn via an indwelling spinal catheter during the sexual response cycle in 10 healthy males and 10 age-matched controls, and analysed for prolactin, oxytocin, biogenic monoamines and/or their metabolites as well as inhibitory and excitatory neurotransmitter concentrations. Parallel to raised peripheral sympathetic activity, norepinephrine also increased in CSF during audiovisual, masturbation-induced sexual arousal and orgasm, and remained elevated for the remainder of the session (F(4,72) = 8.79, P = 0.000). In contrast, none of the other measures, in particular prolactin and dopamine or its metabolites, reflected significant alteration. In conclusion, the human sexual response cycle is characterized by an increase in sympathetic activity in plasma and CSF, and by pronounced secretion of plasma prolactin after orgasm. However, alterations in dopaminergic or peptidergic activity are not found in lumbar CSF, possibly due to local and restricted release in diencephalic and mesencephalic brain regions.

Elevated Prolactin Levels among Adult Male Sex Offenders

A sample of 528 successive admissions to the Phoenix Program, a voluntary inpatient treatment program for sex offenders, was studied in regards to serum prolactin levels. Serum prolactins were obtained as part of a battery of endocrine tests. A substantial number of patients had prolactin levels above the normal range, i.e., 21.0 μg/L. In this sample, fully 10.0% of the men showed elevated prolactin levels (the maximum being 41.0 μg/L), compared with an expected 2.5% according to laboratory norms. None of these individuals had clinical manifestations of prolactinoma. The significance of this increased rate of hyperprolactinemia in this sample of sexual offenders is unclear. There was a negative correlation with age and no correlation with other endocrine tests.

The post-orgasmic prolactin increase following intercourse is greater than following masturbation and suggests greater satiety

Research indicates that prolactin increases following orgasm are involved in a feedback loop that serves to decrease arousal through inhibitory central dopaminergic and probably peripheral processes. The magnitude of post-orgasmic prolactin increase is thus a neurohormonal index of sexual satiety. Using data from three studies of men and women engaging in masturbation or penile-vaginal intercourse to orgasm in the laboratory, we report that for both sexes (adjusted for prolactin changes in a non-sexual control condition), the magnitude of prolactin increase following intercourse is 400% greater than that following masturbation. The results are interpreted as an indication of intercourse being more physiologically satisfying than masturbation, and discussed in light of prior research reporting greater physiological and psychological benefits associated with coitus than with any other sexual activities.

SEXUAL DYSFUNCTION IN WOMEN WITH HYPERPROLACTINEMIA: A PILOT STUDY REPORT

PURPOSE

Hyperprolactinemia is a common hormonal disorder in women that may affect the phases of female sexual function (FSD). We investigated sexual function in patients with hyperprolactinemia.

MATERIAL AND METHODS

A total of 25 women with primary hyperprolactinemia and 16 age matched voluntary healthy women who served as the as control group were evaluated with a detailed medical and sexual history, including a female sexual function index (FSFI) questionnaire and the Beck Depression Inventory. Serum prolactin, dehydroepiandrosterone sulfate, free testosterone, androstenedione, 17alpha-hydroxyprogesterone, estradiol, free thyroxin and thyrotropin were measured. These variables were compared statistically between the 2 groups.

RESULTS

Except for prolactin serum hormone levels in women with hyperprolactinemia were not different from those in the control group. The median total FSFI score was 23.40 (IQR 17.70 to 27.30) in the hyperprolactinemic group, whereas healthy women had a median total FSFI score of 31.10 (IQR 27.55 to 32.88, p < 0.0001). FSD was diagnosed in 22 of 25 patients (88%), while 4 of 16 healthy women (25%) had FSD (p = 0.03). Desire (p = 0.001), arousal (p < 0.0001), lubrication (p = 0.001), orgasm (p = 0.001), satisfaction (p = 0.07) and pain (p = 0.003) domain scores were also significantly lower in women with hyperprolactinemia. Total FSFI (p = 0.009, r = -0.405), desire (p = 0.001, r = -0.512), arousal (p = 0.002, r = -0.466), orgasm (p = 0.026, r = 0.348) and satisfaction (p = 0.041, r = -0.320) scores negatively correlated with mean prolactin but not with the other hormones measured.

CONCLUSIONS

A significant percent of women with hyperprolactinemia whom we evaluated had sexual dysfunction. No hormonal changes other than prolactin and no depression was found as a cause of FSD.

Ecstasy (MDMA) mimics the post-orgasmic state: impairment of sexual drive and function during acute MDMA-effects may be due to increased prolactin secretion

Methylenedioxymethamphetamine (MDMA or "Ecstasy") is a major stimulant drug of abuse worldwide. MDMA produces euphoria, enhances interpersonal communication and feelings of closeness with others. In contrast to the induced emotions of affection and sensual enhancement, clinical studies show that it impairs sexual drive and functioning. In drug-free humans, sexual stimulation with orgasm induces a pronounced secretion of prolactin, which may mediate the post-orgasmic state. The phenomenological features of the psychological state induced by MDMA show some similarities with features of the post-orgasmic state. In addition, MDMA also induces a prominent increase of prolactin plasma levels with a similar time kinetic compared to the post-orgasmic prolactin increase. Here, we present the hypothesis that the impairment of sexual parameters after MDMA may be mediated by increased prolactin.

Prolactinergic and dopaminergic mechanisms underlying sexual arousal and orgasm in humans

Dopaminergic mechanisms play a major role in modulating sexual behavior in humans and animals. Animal data demonstrate important interactions between the dopaminergic and prolactinergic system. As recently demonstrated, dopamine agonists have facilitatory properties for penile erection but may also enhance sexual drive and orgasmic quality. In contrast, chronic elevations of prolactin inhibit appetitive as well as consummatory parameters of sexual behavior. Recent human studies show a marked increase in prolactin after orgasm in males and females. Concerning the biological relevance of acute prolactin alterations after orgasm, prolactin might serve as a neuroendocrine reproductive reflex for peripheral reproductive organs. Alternatively, prolactin may feedback to dopaminergic neurons in the central nervous system and thereby modulate sexual drive and satiation. Here, we provide a brief overview of the physiology of dopamine and prolactin in regulating sexual behavior. In addition, recent experimental and clinical evidence for a postulated feedback mechanism for prolactin and its implications for orgasmic disorders are discussed.

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.

Effects of sexual arousal on lymphocyte subset circulation and cytokine production in man

OBJECTIVE

Sexual arousal and orgasm induce an increase in sympathetic activity as well as in catecholamine and prolactin plasma concentrations. However, the effects of sexual arousal and orgasm on immune functions in man are unknown. Thus, this study investigated the effects of masturbation-induced orgasm on lymphocyte circulation and cytokine production in healthy young males.

METHODS

In a crossover design, 11 volunteers completed an experimental condition in which they were asked to masturbate until orgasm and to participate in a control condition without sexual activity. Blood was drawn continuously for determination of endocrine parameters. In addition, leukocyte and lymphocyte subsets were analyzed via flow cytometry, and the production of lipopolysaccharide-induced interleukin 6 and tumor necrosis factor alpha was measured before and then 5 and 45 min after the orgasm.

RESULTS

The results confirmed transient increases in adrenaline and prolactin plasma concentrations. Sexual arousal and orgasm increased the absolute number of leukocytes, in particular natural killer cells (CD3-CD16+CD56+), in the peripheral blood. In contrast, T cell (CD3+) and B cell (CD3-CD20+) subpopulations as well as the production of interleukin 6 and tumor necrosins factor alpha remained unaffected by sexual activity.

CONCLUSION

These findings demonstrate that components of the innate immune system are activated by sexual arousal and orgasm.

Hyperprolactinaemia and antipsychotic therapy in schizophrenia

Prolactin is a polypeptide hormone that exists as a number of isoforms and is involved in a multitude of physiological processes. Prolactin secretion is promoted by various physiological stimuli and pathological processes and is inhibited by the action of dopamine on the lactotroph cells of the hypothalamus. Hyperprolactinaemia, an elevation of prolactin levels above the norm, is a physiological occurrence and is not of concern (including sexual dysfunction and decreased bone mineral density). Treatment of hyperprolactinaemia is usually confined to the removal of the primary cause of the disease, but several dopamine agonists have been investigated. Hyperprolactinaemia is also a side-effect of the conventional, and some of the second-generation, antipsychotics used in the treatment of schizophrenia. These agents rely on their dopamine antagonistic properties to provide their antipsychotic effects. However, this also removes the brake on prolactin secretion, leading to hyperprolactinaemia. While antipsychotic use has been linked to certain hyperprolactinaemia-related side-effects (sexual dysfunction), its link to others (decreased bone mineral density) has proved more controversial. The association of symptoms with antipsychotic use is further complicated by the fact that patients with schizophrenia can suffer from some of these symptoms because of the disease itself. In managing antipsychotic-induced hyperprolactinaemia, the initial step is to exclude other causes of hyperprolactinaemia while monitoring the occurrence of adverse effects. The physician should also engage in close consultation with the patient with regard to the benefits of the antipsychotic medication and the impact of any adverse effects. A regular risk-benefit discussion will allow the clinician to achieve optimal outcomes in each case.

Acute neuroendocrine response to sexual stimulation in sexual offenders

BACKGROUND

Several pharmacotherapeutic approaches have confirmed the influence of neuroendocrine parameters on sexual desire, function, and fantasies in men; however, the relevance of acute neuroendocrine changes in mediating heightened sexual drive remains unknown. We recently demonstrated that plasma prolactin substantially increases following orgasm in healthy men, suggesting a feedback mechanism for peripheral prolactin in the control of acute sexual arousal. Because prolactin appears to play a regulatory role in acute sexual drive, we initiated this study to see whether sexual offenders with a high sexual drive have a different neuroendocrine response to sexual arousal. This study compares the prolactin response to orgasm of sexual offenders with high sexual drive and that of healthy subjects with average sexual drive.

METHODS

From a subject pool of 150 inpatients held because of sexual crimes, we recruited 10 volunteers, based on their high sexual drive according to an intensive, semistructured clinical interview. We defined sexual drive by a short refractory period and strong sexualization, or a high frequency of sexual stimulation. We analyzed the acute psychoneuroendocrine response to sexual arousal and orgasm continuously before, during, and after masturbation-induced orgasm in patients and control subjects.

RESULTS

Sexual offenders demonstrated higher sexual desire (P < 0.001) and function (P < 0.001) and a more positively perceived refractory period (P < 0.05). Both groups displayed a prolonged, significant increase in prolactin plasma levels after orgasm (P < 0.001). Sexual offenders did not differ from control subjects in neuroendocrine response to sexual arousal and orgasm.

CONCLUSIONS

These data demonstrate that sexual offenders with a high sexual drive do not differ from control subjects in the postorgasmic neuroendocrine response, particularly in prolactin release. This study confirms that factors other than peripheral hormones influence deviant sexual behaviour.

Mating attenuates aging-associated increase of lipid peroxidation activity in C57BL/6J mice

In the frame of the free-radical hypothesis of aging and literature data on increased life span of mated animals, we evaluated brain, kidney, and liver lipid peroxidation in C57Bl/6J mice of various ages and compared lipid peroxidation activity in mated and non-mated mice of both genders. An aging-associated increase (from 3 to 12 months of age) of lipid peroxidation, as measured by malonaldehyde and 4-hydroxyalkenals (MDA + HAE) levels, was observed in the liver and kidney, but not in the brain. Tissue MDA + HAE levels were lower in 12-month old mated mice (housed with animals of opposite gender from three to five months of age) than in 12-month old non-mated animals. There were no gender differences in the observed effect. It is suggested that mating might attenuate the increase of lipid peroxidation associated with aging.

Pregnancy-stimulated neurogenesis in the adult female forebrain mediated by prolactin

Neurogenesis occurs in the olfactory system of the adult brain throughout life, in both invertebrates and vertebrates, but its physiological regulation is not understood. We show that the production of neuronal progenitors is stimulated in the forebrain subventricular zone of female mice during pregnancy and that this effect is mediated by the hormone prolactin. The progenitors then migrate to produce new olfactory interneurons, a process likely to be important for maternal behavior, because olfactory discrimination is critical for recognition and rearing of offspring. Neurogenesis occurs even in females that mate with sterile males. These findings imply that forebrain olfactory neurogenesis may contribute to adaptive behaviors in mating and pregnancy.

High-dose ascorbic acid increases intercourse frequency and improves mood: a randomized controlled clinical trial

BACKGROUND

Ascorbic acid (AA) modulates catecholaminergic activity, decreases stress reactivity, approach anxiety and prolactin release, improves vascular function, and increases oxytocin release. These processes are relevant to sexual behavior and mood.

METHODS

In this randomized double-blind, placebo-controlled 14 day trial of sustained-release AA (42 healthy young adults; 3000 mg/day Cetebe) and placebo (39 healthy young adults), subjects with partners recorded penile-vaginal intercourse (FSI), noncoital partner sex, and masturbation in daily diaries, and also completed the Beck Depression Inventory before and after the trial.

RESULTS

The AA group reported greater FSI (but, as hypothesized, not other sexual behavior) frequency, an effect most prominent in subjects not cohabiting with their sexual partner, and in women. The AA but not placebo group also experienced a decrease in Beck Depression scores.

CONCLUSIONS

AA appears to increase FSI, and the differential benefit to noncohabitants suggests that a central activation or disinhibition, rather than peripheral mechanism may be responsible.

Absence of orgasm-induced prolactin secretion in a healthy multi-orgasmic male subject

In several studies we have recently demonstrated that orgasm induces prolactin secretion in healthy males and females. This suggests that prolactin may form a feedback regulator of the refractory period following orgasm. To examine this position we investigated the prolactin response of a healthy multi-orgasmic male subject. Blood was drawn continuously during masturbation-induced orgasm. The prolactin response of the case-subject was compared with that of nine healthy adult men with a normal refractory period. The case-subject showed no prolactin response to three orgasms. Data from this multi-orgasmic subject support the hypothesized role of plasma prolactin in contributing to sexual-satiation mechanisms.