[h=1]Steroids & Sexual Performance - The Hard Truth[/h]
Animal studies and media headlines have colored the image of testosterone as a barbaric, orgy-inducing, manic-phase hormone that causes civil men to pillage and destroy in the throes of lust-driven rage while sporting anatomically disproportionate erections.[SUP]1-4[/SUP] If such behavior were so dependent upon über-high testosterone surges, then one would conclude that most video game players and developers are spiking testosterone levels that would shame Mr. Olympia contestants.[SUP]5[/SUP]
Before there was interest in using testosterone or anabolic-androgenic steroids (AAS) to promote muscle mass or strength, sages and kings searched desperately for the “male factor” that would restore, enhance or prolong sexual performance.[SUP]6[/SUP] Bizarre recipes containing dried genitals from predatory and promiscuous animals or any plant that is vagina- or penis-shaped abound in ancient literature. It is little different from today’s focus, where erectile dysfunction treatment is one of the most profitable categories in pharmaceutical sales, production and research; muscle hypertrophy and strength enhancement through exogenous factors is essentially taboo, neglected at best.
Researchers Rise to the Occasion
The essence of testosterone research in the fields of attraction, sexual arousal and function, is that testosterone promotes and enables a man to engage in intercourse— be it for enjoyment (recreational) or family planning (procreational). The aspects involved are more than “getting a boner,” though that is a well-studied phenomenon.[SUP]7-9[/SUP] It begins with the effect of testosterone on a man’s ability to “compete” for the attention of a suitable mate; his desire and motivation to attain his desired mate’s interest; confidence and self-esteem sufficient to present himself; anthropometric features of masculinity (e.g., facial, voice, frame, build); dominance as it relates to his area of expertise (e.g., recognized as a leader or authority); libido and sexual desire; ease of arousal (physiologic as well as genital); erectile function; and sexual function (e.g., avoiding premature or delayed ejaculation). Sexual violence is a different topic, tragically present in society and often blamed on “testosterone,” though the research suggests that other associations are much more relevant.
Sure, life is a lot easier if sex is just about “getting a boner,” but most of us don’t live a promiscuous, reality show lifestyle. Further, social conditioning and cues, as well as psychological and relationship issues, complicate the sexual act to the point where many individuals suffer anxiety entering or exiting relationships. In Japan, this has led to a nationwide disinterest in sex with a partner, or at all— a condition called sekkusu shinai shōkōgun or “celibacy syndrome.”[SUP]10[/SUP] In the United States, this has encouraged the trend among young adults and adolescents to “hook up” rather than attempt to experience sexual intercourse as part of a relationship. Hypersexuality is associated with personal distress and functional impairment.[SUP]11[/SUP]Anecdotal reports abound of a frighteningly high number of applicants to online dating sites being married or in a “committed relationship” and seeking affairs, or seeking “hook-ups” with no intention of developing the relationships any further than between the sheets. It is not a new thing.[SUP]12[/SUP]
Body, Mind and Libido
Comparing the sexual disadvantages of hypogonadal men (low testosterone) with the research on testosterone’s effects on related mood, anatomy and physiology, it is clear that men with below normal testosterone are at an “apples to apples” disadvantage to men with normal or slightly supraphysiologic testosterone. This is particularly evident in those who suffered from low testosterone prior to birth or from an early age due to genetic conditions, toxic exposure, trauma or other causes.
For the sake of clarity, consider the issues in general terms: physical development— the body; mood and cognitive effects— the mind; sexual desire and arousal— the libido; erectile and ejaculatory function— the “package.”
Testosterone shapes the physical development of the fetus early in pregnancy, resulting in genital development, mental response to stimuli and programming for later physiologic response to hormonal, metabolic or environmental cues. The development of the penis as a distinctly male structure begins in the seventh week of pregnancy, and continues until approximately the 17th week.[SUP]13[/SUP] This is the time that the fetus begins to produce testosterone and the androgenic metabolite DHT. These hormones are responsible for the development of the penile erectile tissue, scrotum and urethral opening— the “hole” that urine and ejaculate exit.
One issue that is drastically “under the radar” is the effect of endocrine disruptors on the developing fetus in humans. It has been shown that these chemicals, present in our water supply, food packaging, food products and other environmental sources, affect the receptors that respond to estrogens and testosterone. There is observational data suggesting this has negatively affected the development of the human fetus. In addition, animal and tracking data shows that men produce less testosterone than prior generations.[SUP]14-17[/SUP]
Penile Size and Testosterone
Two conditions involving penile size or structure relate (and respond) to testosterone— micropenis and hypospadias. Micropenis is what it sounds like, an abnormally undersized penis, commonly between one-half to one inch in length. Hypospadias is when the urethral opening is not near the end of the penis, but on the underside somewhere closer to the body. Both conditions are treated with testosterone in children, with the greatest response during the infancy or preschool years. With treatment, adult penile length averages 10 centimeters (four inches stretched length, the equivalent of the erect length), whereas “normal” men have an average stretched penile length of 12.4 centimeters (five inches).[SUP]18[/SUP] Yes, there is for the lifetime of most males an interest in penile measurement standards, due to the social reward of being “well hung.” Anxiety about genital size causes many men great distress, and it is not restricted to the Western culture. A sample of 367 men in the military between ages 21 and 40 revealed that “genital self-image” (no, that is not a crotch-selfie posted on social media) was strongly associated with sexual anxiety and erectile dysfunction.[SUP]19[/SUP] A related study on the same group determined that almost nine percent in this group of young to middle-aged adults suffered sexual performance problems, and one-third of all men reported experiencing erectile dysfunction.[SUP]20[/SUP]Clearly, penis size affects not only a man’s actual dimensions, but can also greatly impact his ability to enjoy and perform sexually. This affects not only him, but also his spouse/partner.
Testosterone does not have much additional effect on adult penis size. If it did, the Mr. Olympia competitors would not be wearing those posing trunks onstage. However, testosterone deficiency can reduce the girth and rigidity of the penis. In part, this happens because smooth muscle cells that participate in maintaining an erection are replaced with fat cells.[SUP]21[/SUP] Most people are conditioned to think of Viagra-like drugs (PDE5 inhibitors) to treat erectile dysfunction. Interestingly, PDE5i drugs raise testosterone in addition to dilating blood vessels, and some people still do not respond to PDE5i drugs without testosterone treatment.[SUP]22[/SUP] Raising testosterone within the “normal range” increases the vasodilatory (increasing blood flow) signaling system called eNOS. However, this effect is lost with supraphysiologic testosterone or DHT dosing.[SUP]23[/SUP] This may account for the reports of erectile dysfunction in some individuals misusing anabolic steroids in concentrations well above “normal.”
Other Problems Down Under
Another sexual aspect fascinating to most is ejaculation; an act filled with intense physical, mental and emotional effect. Ejaculation occurs with various delay and stimulation, even for the same person. There is a typical duration of intercourse prior to ejaculating, contrary to locker room bragging about marathon sessions of intercourse. According to published research, the average man ejaculates approximately seven minutes after initiating intercourse.[SUP]24[/SUP] Premature ejaculation, defined as ejaculating quicker than desired and causing distress (within one to two minutes or less), affects between 15 and 20 percent of all adult men.[SUP]24-26[/SUP] Various treatments for premature ejaculation are underway, including topical anesthetics and PDE5i drugs.[SUP]27[/SUP]
One might imagine that premature ejaculators have low testosterone, given the self-imposed shame associated with the condition. However, it is the opposite— they have higher (normal) testosterone; and delayed ejaculation can be a sign of testosterone deficiency.[SUP]28,29 [/SUP]In terms of success as a breeder, those who can complete the act quickly are more likely not to be interrupted by hostile competitors (or a cellphone nowadays), and may be able to “rise to the occasion” again more rapidly.
Attraction is based upon one person's appreciation of another’s physical appearance, implied health and potential, and demeanor. Most research has looked at how women rate a man’s appearance or attraction. It should be of little surprise that there is a lot of variability in response, but some general trends are present. Women are attracted to a man with masculine facial features, voice, broad shoulders, a narrow waist and the implied ability to be healthy and able to work. This is particularly true if they are interested in uncommitted sexual relationships.[SUP]30[/SUP] These features all reflect testosterone’s effect during maturation, as anyone who has had a teenager going through the physical changes of adolescence can attest. Muscle building requires substantially higher testosterone than the average level, so a well-developed body reflects optimally functioning testes.
Arousal, Desire and Sexual Progression
Testosterone is involved in providing a man the equipment, ability and programming to perform sexually. The last ingredient is desire, or becoming aroused. Arousal is often defined as having an erection in a sexual context. However, arousal begins with signs that precede the onset of an erection many times, in underappreciated ways. Animal studies depend upon certain “mating calls” or the production of pheromones. Though it is not as well studied in humans, arousal is the most testosterone-dependent feature of the sexual progression. Based on animal data, it appears that the ability to develop an erection, and “mount” a sexually receptive female is well preserved, even in males with below-normal testosterone. However, being in a “sexy” environment, in and of itself, will not induce arousal as easily when testosterone is low.[SUP]31[/SUP] It is a consideration in diagnosing men with testosterone deficiency. Humans are socially conditioned, and respond to cues that overcome hormonal deficiencies at times. Lack of libido and difficulty in becoming aroused are signs of testosterone deficiency, but many men will not recognize the change as it is insidious (i.e., subtle or slowly progressing), and they develop a routine with a partner of Saturday night sex or whatever as a scheduled event. The arousal is replaced with an expectation based upon cues.
Testosterone is a sex steroid hormone, and has critical functions in that aspect of life for nearly all men. The muscle building and body composition effects are not necessarily relevant to perhaps a majority of adults. However, without adequate testosterone, a highly valued component of life, relationships, and pleasure are detrimentally affected.
References:
1. McGinnis MY. Anabolic androgenic steroids and aggression: studies using animal models. Ann NY Acad Sci 2004;1036:399-415.
2. Turner D, Schöttle D, et al. Assessment methods and management of hypersexuality and paraphilic disorders. Curr Opin Psychiatry 2014;27:413-22.
3. Pope HG Jr, Kouri EM, et al. Effects of supraphysiologic doses of testosterone on mood and aggression in normal men: a randomized controlled trial. Arch Gen Psychiatry. 2000;57:133-40;155-6.
4. Herbert J. How raging hormones can turn a red-hot male blue … and help you on the trading floor, on the sport's field or in an election. Daily Mail. April 30, 2015. www.dailymail.co.uk/home/books/arti...elp-trading-floor-sport-s-field-election.html, accessed May 27, 2015.
5. Beck VS, Boys S, et al. Violence against women in video games: a prequel or sequel to rape myth acceptance? J Interpers Violence 2012;27:3016-31.
6. Shamloul R. Natural aphrodisiacs. J Sex Med 2010;7:39-49.
7. Traish AM, Guay AT. Are androgens critical for penile erections in humans? Examining the clinical and preclinical evidence. J Sex Med 2006;3:382-404;404-7.
8. Traish A, Kim N. The physiological role of androgens in penile erection: regulation of corpus cavernosum structure and function. J Sex Med 2005;2:759-70.
9. Alexander GM, Swerdloff RS, et al. Androgen-behavior correlations in hypogonadal men and eugonadal men. I. Mood and response to auditory sexual stimuli. Horm Behav 1997;31:110-9.
10. Haworth A. Why have young people in Japan stopped having sex? The Guardian October 20, 2013. www.theguardian.com/world/2013/oct/20/young-people-japan-stopped-having-sex, access June 2, 2015.
11. Spenhoff M, Kruger TH, et al. Hypersexual behavior in an online sample of males: associations with personal distress and functional impairment. J Sex Med 2013;10:2996-3005.
12. Dowsett GW. “And next, just for your enjoyment!”: sex, technology and the constitution of desire. Cult Health Sex 2015;17:527-39.
13. Yiee JH, Baskin LS. Penile embryology and anatomy. Scientific World Journal 2010;10:1174-9.
14. El Kholy M, Hamza RT, et al. Penile length and genital anomalies in Egyptian male newborns: epidemiology and influence of endocrine disruptors. J Pediatr Endocrinol Metab 2013;26:509-13.
15. Gaspari L, Sampaio DR, et al. High prevalence of micropenis in 2710 male newborns from an intensive-use pesticide area of Northeastern Brazil. Int J Androl 2012;35:253-64.
16. Sonne C, Dyck M, et al. Penile density and globally used chemicals in Canadian and Greenland polar bears. Environ Res 2015;137:287-91.
17. Travison TG, Araujo AB, et al. Temporal trends in testosterone levels and treatment in older men. Curr Opin Endocrinol Diabetes Obes 2009;16:211-7.
18. Bin-Abbas B, Conte FA, et al. Congenital hypogonadotropic hypogonadism and micropenis: effect of testosterone treatment on adult penile size why sex reversal is not indicated. J Pediatr 1999;134:579-83.
19. Wilcox SL, Redmond S, et al. Genital image, sexual anxiety, and erectile dysfunction among young male military personnel. J Sex Med 2015 Apr 30. [Epub, ahead of print]
20. Wilcox SL, Redmond S, et al. Sexual functioning in military personnel: preliminary estimates and predictors. J Sex Med 2014;11:2537-45.
21. Traish A, Kim N. The physiological role of androgens in penile erection: regulation of corpus cavernosum structure and function. J Sex Med 2005;2:759-70.
22. Spitzer M, Bhasin S, et al. Sildenafil increases serum testosterone levels by a direct action on the testes. Andrology 2013;1:913-8.
23. Goglia L, Tosi V, et al. Endothelial regulation of eNOS, PAI-1 and t-PA by testosterone and dihydrotestosterone in vitro and in vivo. Mol Hum Reprod 2010;16:761-9.
24. Patrick DL, Althof SE. et al. Premature ejaculation: an observational study of men and their partners. J Sex Med 2005;2:358-67.
25. Rowland D, Perelman M, et al. Self-reported premature ejaculation and aspects of sexual functioning and satisfaction. J Sex Med 2004;1:225-32.
26. Son H, Song SH, et al. Self-reported premature ejaculation prevalence and characteristics in Korean young males: community-based data from an Internet survey. J Androl 2010;31:540-6.
27. Aversa A, Pili M, et al. Effects of vardenafil administration on intravaginal ejaculatory latency time in men with lifelong premature ejaculation. Int J Impot Res 2009;21:221-7.
28. Lotti F, Corona G, et al. Clinical correlates of erectile dysfunction and premature ejaculation in men with couple infertility. J Sex Med 2012;9:2698-707.
29. Corona G, Jannini EA, et al. Different testosterone levels are associated with ejaculatory dysfunction. J Sex Med 2008;5:1991-8.
30. Boothroyd LG, Brewer G. Self-reported impulsivity, rather than sociosexuality, predicts women's preferences for masculine features in male faces. Arch Sex Behav 2014;43:983-8.
31. Harding SM, Velotta JP. Comparing the relative amount of testosterone required to restore sexual arousal, motivation, and performance in male rats. Horm Behav 2011;59:666-73.
Animal studies and media headlines have colored the image of testosterone as a barbaric, orgy-inducing, manic-phase hormone that causes civil men to pillage and destroy in the throes of lust-driven rage while sporting anatomically disproportionate erections.[SUP]1-4[/SUP] If such behavior were so dependent upon über-high testosterone surges, then one would conclude that most video game players and developers are spiking testosterone levels that would shame Mr. Olympia contestants.[SUP]5[/SUP]
Before there was interest in using testosterone or anabolic-androgenic steroids (AAS) to promote muscle mass or strength, sages and kings searched desperately for the “male factor” that would restore, enhance or prolong sexual performance.[SUP]6[/SUP] Bizarre recipes containing dried genitals from predatory and promiscuous animals or any plant that is vagina- or penis-shaped abound in ancient literature. It is little different from today’s focus, where erectile dysfunction treatment is one of the most profitable categories in pharmaceutical sales, production and research; muscle hypertrophy and strength enhancement through exogenous factors is essentially taboo, neglected at best.
Researchers Rise to the Occasion
The essence of testosterone research in the fields of attraction, sexual arousal and function, is that testosterone promotes and enables a man to engage in intercourse— be it for enjoyment (recreational) or family planning (procreational). The aspects involved are more than “getting a boner,” though that is a well-studied phenomenon.[SUP]7-9[/SUP] It begins with the effect of testosterone on a man’s ability to “compete” for the attention of a suitable mate; his desire and motivation to attain his desired mate’s interest; confidence and self-esteem sufficient to present himself; anthropometric features of masculinity (e.g., facial, voice, frame, build); dominance as it relates to his area of expertise (e.g., recognized as a leader or authority); libido and sexual desire; ease of arousal (physiologic as well as genital); erectile function; and sexual function (e.g., avoiding premature or delayed ejaculation). Sexual violence is a different topic, tragically present in society and often blamed on “testosterone,” though the research suggests that other associations are much more relevant.
Sure, life is a lot easier if sex is just about “getting a boner,” but most of us don’t live a promiscuous, reality show lifestyle. Further, social conditioning and cues, as well as psychological and relationship issues, complicate the sexual act to the point where many individuals suffer anxiety entering or exiting relationships. In Japan, this has led to a nationwide disinterest in sex with a partner, or at all— a condition called sekkusu shinai shōkōgun or “celibacy syndrome.”[SUP]10[/SUP] In the United States, this has encouraged the trend among young adults and adolescents to “hook up” rather than attempt to experience sexual intercourse as part of a relationship. Hypersexuality is associated with personal distress and functional impairment.[SUP]11[/SUP]Anecdotal reports abound of a frighteningly high number of applicants to online dating sites being married or in a “committed relationship” and seeking affairs, or seeking “hook-ups” with no intention of developing the relationships any further than between the sheets. It is not a new thing.[SUP]12[/SUP]
Body, Mind and Libido
Comparing the sexual disadvantages of hypogonadal men (low testosterone) with the research on testosterone’s effects on related mood, anatomy and physiology, it is clear that men with below normal testosterone are at an “apples to apples” disadvantage to men with normal or slightly supraphysiologic testosterone. This is particularly evident in those who suffered from low testosterone prior to birth or from an early age due to genetic conditions, toxic exposure, trauma or other causes.
For the sake of clarity, consider the issues in general terms: physical development— the body; mood and cognitive effects— the mind; sexual desire and arousal— the libido; erectile and ejaculatory function— the “package.”
Testosterone shapes the physical development of the fetus early in pregnancy, resulting in genital development, mental response to stimuli and programming for later physiologic response to hormonal, metabolic or environmental cues. The development of the penis as a distinctly male structure begins in the seventh week of pregnancy, and continues until approximately the 17th week.[SUP]13[/SUP] This is the time that the fetus begins to produce testosterone and the androgenic metabolite DHT. These hormones are responsible for the development of the penile erectile tissue, scrotum and urethral opening— the “hole” that urine and ejaculate exit.
One issue that is drastically “under the radar” is the effect of endocrine disruptors on the developing fetus in humans. It has been shown that these chemicals, present in our water supply, food packaging, food products and other environmental sources, affect the receptors that respond to estrogens and testosterone. There is observational data suggesting this has negatively affected the development of the human fetus. In addition, animal and tracking data shows that men produce less testosterone than prior generations.[SUP]14-17[/SUP]
Penile Size and Testosterone
Two conditions involving penile size or structure relate (and respond) to testosterone— micropenis and hypospadias. Micropenis is what it sounds like, an abnormally undersized penis, commonly between one-half to one inch in length. Hypospadias is when the urethral opening is not near the end of the penis, but on the underside somewhere closer to the body. Both conditions are treated with testosterone in children, with the greatest response during the infancy or preschool years. With treatment, adult penile length averages 10 centimeters (four inches stretched length, the equivalent of the erect length), whereas “normal” men have an average stretched penile length of 12.4 centimeters (five inches).[SUP]18[/SUP] Yes, there is for the lifetime of most males an interest in penile measurement standards, due to the social reward of being “well hung.” Anxiety about genital size causes many men great distress, and it is not restricted to the Western culture. A sample of 367 men in the military between ages 21 and 40 revealed that “genital self-image” (no, that is not a crotch-selfie posted on social media) was strongly associated with sexual anxiety and erectile dysfunction.[SUP]19[/SUP] A related study on the same group determined that almost nine percent in this group of young to middle-aged adults suffered sexual performance problems, and one-third of all men reported experiencing erectile dysfunction.[SUP]20[/SUP]Clearly, penis size affects not only a man’s actual dimensions, but can also greatly impact his ability to enjoy and perform sexually. This affects not only him, but also his spouse/partner.
Testosterone does not have much additional effect on adult penis size. If it did, the Mr. Olympia competitors would not be wearing those posing trunks onstage. However, testosterone deficiency can reduce the girth and rigidity of the penis. In part, this happens because smooth muscle cells that participate in maintaining an erection are replaced with fat cells.[SUP]21[/SUP] Most people are conditioned to think of Viagra-like drugs (PDE5 inhibitors) to treat erectile dysfunction. Interestingly, PDE5i drugs raise testosterone in addition to dilating blood vessels, and some people still do not respond to PDE5i drugs without testosterone treatment.[SUP]22[/SUP] Raising testosterone within the “normal range” increases the vasodilatory (increasing blood flow) signaling system called eNOS. However, this effect is lost with supraphysiologic testosterone or DHT dosing.[SUP]23[/SUP] This may account for the reports of erectile dysfunction in some individuals misusing anabolic steroids in concentrations well above “normal.”
Other Problems Down Under
Another sexual aspect fascinating to most is ejaculation; an act filled with intense physical, mental and emotional effect. Ejaculation occurs with various delay and stimulation, even for the same person. There is a typical duration of intercourse prior to ejaculating, contrary to locker room bragging about marathon sessions of intercourse. According to published research, the average man ejaculates approximately seven minutes after initiating intercourse.[SUP]24[/SUP] Premature ejaculation, defined as ejaculating quicker than desired and causing distress (within one to two minutes or less), affects between 15 and 20 percent of all adult men.[SUP]24-26[/SUP] Various treatments for premature ejaculation are underway, including topical anesthetics and PDE5i drugs.[SUP]27[/SUP]
One might imagine that premature ejaculators have low testosterone, given the self-imposed shame associated with the condition. However, it is the opposite— they have higher (normal) testosterone; and delayed ejaculation can be a sign of testosterone deficiency.[SUP]28,29 [/SUP]In terms of success as a breeder, those who can complete the act quickly are more likely not to be interrupted by hostile competitors (or a cellphone nowadays), and may be able to “rise to the occasion” again more rapidly.
Attraction is based upon one person's appreciation of another’s physical appearance, implied health and potential, and demeanor. Most research has looked at how women rate a man’s appearance or attraction. It should be of little surprise that there is a lot of variability in response, but some general trends are present. Women are attracted to a man with masculine facial features, voice, broad shoulders, a narrow waist and the implied ability to be healthy and able to work. This is particularly true if they are interested in uncommitted sexual relationships.[SUP]30[/SUP] These features all reflect testosterone’s effect during maturation, as anyone who has had a teenager going through the physical changes of adolescence can attest. Muscle building requires substantially higher testosterone than the average level, so a well-developed body reflects optimally functioning testes.
Arousal, Desire and Sexual Progression
Testosterone is involved in providing a man the equipment, ability and programming to perform sexually. The last ingredient is desire, or becoming aroused. Arousal is often defined as having an erection in a sexual context. However, arousal begins with signs that precede the onset of an erection many times, in underappreciated ways. Animal studies depend upon certain “mating calls” or the production of pheromones. Though it is not as well studied in humans, arousal is the most testosterone-dependent feature of the sexual progression. Based on animal data, it appears that the ability to develop an erection, and “mount” a sexually receptive female is well preserved, even in males with below-normal testosterone. However, being in a “sexy” environment, in and of itself, will not induce arousal as easily when testosterone is low.[SUP]31[/SUP] It is a consideration in diagnosing men with testosterone deficiency. Humans are socially conditioned, and respond to cues that overcome hormonal deficiencies at times. Lack of libido and difficulty in becoming aroused are signs of testosterone deficiency, but many men will not recognize the change as it is insidious (i.e., subtle or slowly progressing), and they develop a routine with a partner of Saturday night sex or whatever as a scheduled event. The arousal is replaced with an expectation based upon cues.
Testosterone is a sex steroid hormone, and has critical functions in that aspect of life for nearly all men. The muscle building and body composition effects are not necessarily relevant to perhaps a majority of adults. However, without adequate testosterone, a highly valued component of life, relationships, and pleasure are detrimentally affected.
References:
1. McGinnis MY. Anabolic androgenic steroids and aggression: studies using animal models. Ann NY Acad Sci 2004;1036:399-415.
2. Turner D, Schöttle D, et al. Assessment methods and management of hypersexuality and paraphilic disorders. Curr Opin Psychiatry 2014;27:413-22.
3. Pope HG Jr, Kouri EM, et al. Effects of supraphysiologic doses of testosterone on mood and aggression in normal men: a randomized controlled trial. Arch Gen Psychiatry. 2000;57:133-40;155-6.
4. Herbert J. How raging hormones can turn a red-hot male blue … and help you on the trading floor, on the sport's field or in an election. Daily Mail. April 30, 2015. www.dailymail.co.uk/home/books/arti...elp-trading-floor-sport-s-field-election.html, accessed May 27, 2015.
5. Beck VS, Boys S, et al. Violence against women in video games: a prequel or sequel to rape myth acceptance? J Interpers Violence 2012;27:3016-31.
6. Shamloul R. Natural aphrodisiacs. J Sex Med 2010;7:39-49.
7. Traish AM, Guay AT. Are androgens critical for penile erections in humans? Examining the clinical and preclinical evidence. J Sex Med 2006;3:382-404;404-7.
8. Traish A, Kim N. The physiological role of androgens in penile erection: regulation of corpus cavernosum structure and function. J Sex Med 2005;2:759-70.
9. Alexander GM, Swerdloff RS, et al. Androgen-behavior correlations in hypogonadal men and eugonadal men. I. Mood and response to auditory sexual stimuli. Horm Behav 1997;31:110-9.
10. Haworth A. Why have young people in Japan stopped having sex? The Guardian October 20, 2013. www.theguardian.com/world/2013/oct/20/young-people-japan-stopped-having-sex, access June 2, 2015.
11. Spenhoff M, Kruger TH, et al. Hypersexual behavior in an online sample of males: associations with personal distress and functional impairment. J Sex Med 2013;10:2996-3005.
12. Dowsett GW. “And next, just for your enjoyment!”: sex, technology and the constitution of desire. Cult Health Sex 2015;17:527-39.
13. Yiee JH, Baskin LS. Penile embryology and anatomy. Scientific World Journal 2010;10:1174-9.
14. El Kholy M, Hamza RT, et al. Penile length and genital anomalies in Egyptian male newborns: epidemiology and influence of endocrine disruptors. J Pediatr Endocrinol Metab 2013;26:509-13.
15. Gaspari L, Sampaio DR, et al. High prevalence of micropenis in 2710 male newborns from an intensive-use pesticide area of Northeastern Brazil. Int J Androl 2012;35:253-64.
16. Sonne C, Dyck M, et al. Penile density and globally used chemicals in Canadian and Greenland polar bears. Environ Res 2015;137:287-91.
17. Travison TG, Araujo AB, et al. Temporal trends in testosterone levels and treatment in older men. Curr Opin Endocrinol Diabetes Obes 2009;16:211-7.
18. Bin-Abbas B, Conte FA, et al. Congenital hypogonadotropic hypogonadism and micropenis: effect of testosterone treatment on adult penile size why sex reversal is not indicated. J Pediatr 1999;134:579-83.
19. Wilcox SL, Redmond S, et al. Genital image, sexual anxiety, and erectile dysfunction among young male military personnel. J Sex Med 2015 Apr 30. [Epub, ahead of print]
20. Wilcox SL, Redmond S, et al. Sexual functioning in military personnel: preliminary estimates and predictors. J Sex Med 2014;11:2537-45.
21. Traish A, Kim N. The physiological role of androgens in penile erection: regulation of corpus cavernosum structure and function. J Sex Med 2005;2:759-70.
22. Spitzer M, Bhasin S, et al. Sildenafil increases serum testosterone levels by a direct action on the testes. Andrology 2013;1:913-8.
23. Goglia L, Tosi V, et al. Endothelial regulation of eNOS, PAI-1 and t-PA by testosterone and dihydrotestosterone in vitro and in vivo. Mol Hum Reprod 2010;16:761-9.
24. Patrick DL, Althof SE. et al. Premature ejaculation: an observational study of men and their partners. J Sex Med 2005;2:358-67.
25. Rowland D, Perelman M, et al. Self-reported premature ejaculation and aspects of sexual functioning and satisfaction. J Sex Med 2004;1:225-32.
26. Son H, Song SH, et al. Self-reported premature ejaculation prevalence and characteristics in Korean young males: community-based data from an Internet survey. J Androl 2010;31:540-6.
27. Aversa A, Pili M, et al. Effects of vardenafil administration on intravaginal ejaculatory latency time in men with lifelong premature ejaculation. Int J Impot Res 2009;21:221-7.
28. Lotti F, Corona G, et al. Clinical correlates of erectile dysfunction and premature ejaculation in men with couple infertility. J Sex Med 2012;9:2698-707.
29. Corona G, Jannini EA, et al. Different testosterone levels are associated with ejaculatory dysfunction. J Sex Med 2008;5:1991-8.
30. Boothroyd LG, Brewer G. Self-reported impulsivity, rather than sociosexuality, predicts women's preferences for masculine features in male faces. Arch Sex Behav 2014;43:983-8.
31. Harding SM, Velotta JP. Comparing the relative amount of testosterone required to restore sexual arousal, motivation, and performance in male rats. Horm Behav 2011;59:666-73.
