Are men aware of normal penile length and sexual function? A narrative review of the literature

Abstract

Men frequently present to their health practitioners with concerns that they are not “normal” in the domains of sexual anatomy and function. This narrative review aims to synthesize the existing evidence on the general male population’s perception of normative sexual anatomy (penile length) and function (erectile and ejaculatory function). A structured literature search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, limited to English language studies that involved adult participants from non-medical backgrounds. Of the 1098 studies identified, only seven met the predefined inclusion and exclusion criteria, indicating an insufficiency in research directly addressing men’s perceptions of normative sexual anatomy and function. The studies included in this review found that there was an inaccurate understanding of what empirically constitutes “normal”. Men considered above-average penis lengths to be common and perceived themselves as “small” despite being within the normal range. They tended to overestimate typical intercourse durations and were inaccurate in self-diagnosing ejaculatory dysfunction and erectile dysfunction. The inability to differentiate normal and abnormal sexual function reflects a poor understanding of what constitutes normal. These findings may inform future research and provide guidance for educating clinicians and the public to improve sexual health.

INTRODUCTION

Men often visit their health practitioners with concerns that they are not “normal” concerning sexual anatomy or function.1 These concerns encompass various domains, including penile length or girth, libido, erectile function, and time to ejaculation. While the normal distribution of these parameters has been established empirically,2,3,4,5 it is unclear what the general male population perceives as “normal”.

Pornography is one source of misinformation regarding sexual activity. Unrealistic depictions of male anatomy and intercourse form the basis of sexual education for many, fostering unrealistic expectations.6 However, some countries limit access to pornography for political, cultural, or religious reasons. In such places, pornography may minimally impact their perception. Instead, other sources of misinformation, such as unrealistic portrayals of sex in popular media, contribute to inflated expectations.7 Furthermore, comparison among peers and social interactions where men are ridiculed regarding their sexual ability or genitalia may negatively influence perceptions. Similar sociopolitical dynamics may restrict sexual education in schools in some countries.8,9 As a consequence, men may have a skewed perception of what is normal. This dissatisfaction is reflected in a study finding that 68% of men desired a larger penis.10 These concerns may be exacerbated by the association of sexual ability and penile size with masculinity by popular media11 and the significant historical and cultural significance placed upon sexual function and penile size.12 Therefore, men consider sexual function and anatomy to be important, and a distorted understanding of normal parameters may result in negative self-perception and insecurity.13 Conditions that are associated with significant anxiety, such as small-penis syndrome,14 may develop. Furthermore, lack of awareness may be a barrier in accessing the treatment for sexual dysfunctions, which are associated with depression and anxiety.5

This narrative review aims to synthesize the existing evidence regarding the general male population’s perception of normative sexual anatomy and function. This would be compared with the empirical standard to determine if there is an inaccurate understanding of what constitutes “normal.” Normative is defined as what is assumed to be normal and will be inferred from the findings of the studies included in the review. In contrast, the empirical “normal” will be determined more objectively by scientific articles. Additionally, this review aims to briefly explore the implications of these findings on sexual health practice and education, as well as directions for future research.

METHODS

A structured literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Three electronic databases were explored, including Ovid Medline, PsycINFO, and CINAHL. The key terms of the search included “male”, “sexual anatomy”, “sexual function”, “penis length”, “erectile function”, “premature ejaculation”, “survey”, “awareness”, and “perception”. English language studies published before June 2025 were considered.

The criteria for inclusion were studies written in English, involving male participants aged 18 years or above, and assessing participants’ perception and awareness of normal male sexual anatomy and function. Studies were excluded if recruited participants had medical backgrounds or if they solely assessed epidemiology, pathology, or awareness of management options for male sexual dysfunctions. Titles and abstracts were reviewed, and studies meeting the inclusion criteria were retrieved in full. Relevant studies were then included in this review. The reference lists of relevant studies were manually examined to identify additional studies not identified in the electronic search.

RESULTS

A total of 1098 studies were identified through the search after duplicates were removed. Following title and abstract scanning, 32 reports were retrieved for further review, and seven additional studies were identified through a manual search of reference lists, resulting in a total of 39 studies for full-text review. A total of seven studies were included in this review; these fulfilled the inclusion criteria and were relevant to the theme of the search. Figure 1 summarizes the search strategy and screening process. Table 1 summarizes the methodologies and results of the included studies.

Figure 1.

PRISMA flowchart of study screening and selection. PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

Table 1.

Summary of the included studies

Studya	Participantsb	Methodologyc	Relevant findingsd
Mondaini et al.15 2002 (Italy)	67 men; median age: 27 years, range: 16–55 years; penile length	Mixed qualitative-quantitative/history focused on the time of onset and perceived reason for “short penis” concerns, participants asked to estimate measurement of “normal” sized penis, genital exam and measurement of penile length and circumference in flaccid and fully stretched states	Penile length  44 patients (65.7%) complained of short penis only in flaccid state, and 22 patients (32.8%) complained of short penis in both flaccid and erect state  57 men (85%) over-estimated the “normal” penis size in flaccid state as being 12 cm; 10 patients (15%) had no idea of a “normal” penis length  None of the participants were under the 2.5 percentile of the penis length nomogram; 89.5% (flaccid) and 91% (erect) of patients were between the 10th and 90th percentile in penis length
Sanches et al.16 2018 (Brazil)	689 men; mean age: 59.64 (s.d.: 9.66) years; penile length	Mixed qualitative–quantitative cross-sectional study/IIEF-5 questionnaire, objective penile length, subjective penile size	Penile length  Penis objective length (stretched flaccid) was 13.08±2.32 cm (mean±s.d.) and 67 (9.72%) patients referred small penis self-perception  Mean objective penile length was not different when comparing patients that have the subjective impression of small (12.94 cm) and normal (13.48 cm) penis (P=0.54)
Shaeer and Shaeer17 2012 (Egypt)	804 men; mean age: 35.2 (s.d.: 7.6; range: 20–65) years; premature ejaculation and penile length	Mixed qualitative–quantitative Internet-based survey/total of 66 questions regarding ejaculatory control, IELT and related distress and expectations, penile erect length, satisfaction with penile size, expectations of normal size etc.	Premature ejaculation  82.6% subjectively reported premature ejaculation  Self-reported IELT was 9.06±10.2 min (mean±s.d.), with a median of 5 (95% CI: 8.4–9.8) min  Male subjects also reported that the expected normal for this domain was 16.5±12.9 min (mean±s.d.), and median: 15 (95% CI: 15.6–17.4) min  There is a 66.7% difference from their self-reported median (P<0.001) Penile length  Self-measured erect penile length from pubic symphysis to glans (mean±s.d.: 15.6±4.1 cm; 95% CI: 15.4–15.9 cm). This was not significantly different from expected normal penile length (mean ± s.d.: 15.9 ± 4 cm)  OR for having ED and dissatisfaction with penile size was 4.5 (95% CI: 2.4–8.6)  Males with concerns over penile size had a statistically significant shorter length (mean±s.d.: 12.1±3.9 cm) compared to the unconcerned (mean±s.d.: 15.9±4 cm; P<0.001)
McMahon et al.22 2012 (Australia and Asia-Pacific region)	4997 men; 43% aged 18–35 years, 25% aged 36–45 years, and 21% aged 46–55 years; premature ejaculation and ED	Qualitative survey done online or in-person (survey and recruitment methodologies varied by location)/total of 48 questions including PEDT, SHIM, and IPE. Separately, men self-reported having premature ejaculation or ED	Premature ejaculation  PEDT diagnosed PE in 16% of respondents and probable PE in a further 15%; however, only 13% self-reported PE  The majority of respondents with PEDT-diagnosed PE (60%) and probable PE (81%) self-reported as not having PE  Most frequently self-reported IELT was 5–10 min  34% of respondents with PEDT-diagnosed PE self-reported IELTs of more than 5 min and 14% reported IELTs of more than 10 min  Only 11% of men with PEDT-diagnosed PE and 7% of men with probable PE reported an IELT of 1 min or less ED  More respondents self-reported ED (8%) than had SHIM-diagnosed moderate or severe ED (5%)
Wang et al.26 2024 (China)	592 men (control; n=126; PE: n=466); mean age: 29.6 (s.d.: 6.2) years; premature ejaculation	Qualitative survey performed in-person and detailed assessment of participant’s sexual function performed by health care providers, including PEDT score, self-assessed IELT at baseline (PIELT), subjective perception of NIELT and EIELT after PE treatment	Premature ejaculation  The mean PIELT of the PE and control groups were 1.6±1.3 min and 14.5±6.7 min (mean±s.d.), respectively; the control group reported their PIELT to be “normal”  The mean NIELT for the PE group was 14.0±7.1 min (mean±s.d.)  The mean EIELT in the PE and the control groups were 15.4±7.5 min and 19.1±7.2 min (mean±s.d.), respectively; the control group’s EIELT is 5 min longer than the PE group’s EIELT  In the PE group, 69.5% reported an EIELT equal or greater to NIELT.   Indicating that they expect PE treatment to result in better sexual performance than what they consider normal  There is a strong positive correlation between NIELT and EIELT in patients with PE, with correlation coefficient of 0.844; this suggests that EIELT is influenced by NIELT and inaccurate expectations of normal can create unrealistic expectations
Takeuchi et al.27 2021 (Japan)	66 men; mean age: 60 years, range: 40–69 years; ED	Cross-sectional mixed qualitative and quantitative self-administered survey distributed at suburban family medicine clinic/11-item survey addressing sexual dysfunction including self-report, IIEF-5 and open-ended questioning	ED  39% (26/66) self-reported having sexual dysfunction; 92% met ED criteria of the IIEF-5: mild (n=27), mild-to-moderate (n=15), moderate (n=7), or severe (n=12)  Common themes among written comments were considering sexual dysfunction as normal aging (unaware that sexual dysfunction is a medical problem) and attributing sexual dysfunction to decreased libido
Shabsigh et al.28 2010 (USA)	1053 men; mean age: 52 years, range: 29–85 years; ED	Mixed qualitative and quantitative survey/screening question “do you have ED?” and IIEF-EF were administered	ED  139 men responded “yes” to the ED screening question; of these, 96% had IIEF-EF scores consistent with some degree of ED  Of 388 men who answered “no” to the screening question, 36% also had IIEF-EF scores which indicated some degree of ED  Of 526 men who answered “unsure” to the screening question, 90% had IIEF-EF scores which indicated some degree of ED

^aAuthor(s), year of publication (country of study). ^bNumber of participants/age profile/aspect of sexual anatomy or function awareness investigated (i.e., penis length/ED/premature ejaculation). ^cType of study/study design and outcome measures. ^dSome studies were broader in scope, so only relevant outcome measures to assessing patient awareness were extracted). PE: premature ejaculation; ED: erectile dysfunction; PEDT: Premature Ejaculation Diagnostic Tool; IPE: Index of Premature Ejaculation; IIEF-5: International Index of Erectile Function-5; IIEF-EF: IIEF-erectile function domain; PIELT: self-assessed IELT at baseline; IELT: intravaginal ejaculatory latency time; EIELT: expected IELT after PE treatment; NIELT: normal IELT; SHIM: Sexual Health Inventory for Men; ISSM: International Society of Sexual Medicine; s.d.: standard deviation; CI: confidence interval; OR: odds ratio

The seven studies included in this review represented diverse populations from various countries, including Italy, Brazil, Egypt, Japan, America, Australia, China, and other countries in the Asia-Pacific region. There was a wide distribution in participants’ age across the studies (Table 1). In total, three articles assessed perception of normal sexual anatomy concerning penile length, three articles assessed perception of normal ejaculatory function through assessing premature ejaculation (PE), and three articles assessed perception of normal erectile function by assessing erectile dysfunction (ED). All studies included in this review were mixed quantitative and qualitative cross-sectional studies. In most of the studies, assessing perception was not a primary aim and was indirectly inferred from the outcomes.

Mondaini et al.15 assessed the penile length of 67 Italian men attending an andrological clinic with concerns of a “short penis”.

Regarding objective penile length, in the study by Mondaini et al.,15 physicians recorded flaccid and fully stretched, but not erect, lengths. Penile length was defined as the linear distance along the dorsal side of the penis extending from the pubopenile skin junction to the tip of the glans. It was found that 89.5% of participants when flaccid, and 91% when stretched, fell between the 10^th percentile (6.5 cm flaccid and 9 cm stretched) and the 90^th percentile (11 cm flaccid and 15 cm stretched) in penile length. These measurements are congruent with those described in a systematic review exploring penile length by Veale et al.,3 therefore could be considered within the range of “normal” penile length. Despite this, Mondaini et al.15 found 65.7% of the participants complained of “short penis” in the flaccid state, while 32.8% complained in both the flaccid and erect state. It should be noted that Veale et al.3 and Mondaini et al.15 measured penile lengths using the same technique. Furthermore, Mondaini et al.15 found that 85% of the participants overestimated the length of a “normal” penis in a flaccid state as being 12 (range: 10–17) cm, which corresponds to the 95^th percentile on the nomogram, and 10% were unable to estimate a “normal” length. This highlights that participants had an inaccurate, positively skewed perception of penile length and often perceived themselves as having a “short penis” despite being within the normative range.

Sanches et al.16 performed a cross-sectional study involving 689 men during a routine urological evaluation in Brazil, which assessed participants’ penile length.

In this study, urologists measured objective penile length using a rigid centimeter scale ruler located in the pubic region and stretched until the penis tip. Sanches et al.16 found that objective penis length was 13.08 ± 2.32 cm (mean ± standard deviation [s.d.]) in the stretched flaccid state. Despite differing techniques, this finding is similar to those recorded by Mondaini et al.15 and also congruent with the findings in the systematic review by Veale et al.3 However, Sanches et al.16 found significantly lower rates of small penis self-perception or dissatisfaction compared to Mondaini et al.,15 with a rate of 9.72%. Regarding perception of normative penile length, Sanches et al.16 found that mean objective penile length was not significantly different when comparing patients who have self-perception of “small” (12.94 cm) and “normal” (13.48 cm) penis (P = 0.54). Therefore, similarly to Mondaini et al.,15 participants who were objectively within the normative range of penile length subjectively perceived themselves to be “small”.

The study by Shaeer and Shaeer17 had 804 male participants and involved an Internet-based survey among Arabic-speaking Internet users in the Middle East and Egypt, which assessed participants’ penile length and ejaculatory function.

Regarding penile length, Shaeer and Shaeer17 found that participants’ self-measured erect penile length from pubic symphysis to glans was 15.6 ± 4.1 cm (mean ± s.d.; 95% confidence interval [CI]: 15.4–15.9 cm). This is significantly greater than the measurements from Mondaini et al.15 and Sanches et al.16 as well as the mean of 13.12 cm identified in a systematic review by Veale et al.3 This difference could be due to ethnic variation in penile length as suggested by Lynn18 and Mostafaei et al.19 However, there is contention to this as Veale et al.3 did not find a significant difference between racial groups. The difference may be due to Shaeer and Shaeer17 measuring erect penile length, whereas the previous two studies measured stretched flaccid length. Alternatively, social desirability and volunteer bias could contribute to this difference as this study’s methodology involved participant self-measure reported through an Internet survey as opposed to objective measurement by a researcher in clinical settings, as seen in the studies by Mondaini et al.15 and Sanches et al.16 Furthermore, the discrepancies may be due to imprecise measurement methodology by the participants.

Despite participants self-reporting larger than average penile lengths, Shaeer and Shaeer17 found a 30% rate of small penis self-perception or dissatisfaction. They also found that participants expected normal penile length to be 15.9 ± 4 cm (mean ± s.d.), and it was found that participants dissatisfied with the size of their penis had a penile length of 12.1 ± 3.9 cm (mean ± s.d.), which could be considered within the range of normal at the 25^th percentile. Therefore, similar to the findings by Mondaini et al.15 and Sanches et al.,16 the participants had an inaccurate perception of “normal” penile length and had a self-perception of a small penis despite being within the normal range.

Regarding ejaculatory function, participants’ self-reported intravaginal ejaculatory latency time (IELT) was 9.06 ± 10.2 min (mean ± s.d.), with a median time of 5 min. These IELT measurements were similar to empirical findings in a larger study by Waldinger et al.2 which implies that the participants were essentially “normal” in time to ejaculation. However, 82.6% of participants subjectively self-reported PE of varying degrees of severity, despite their IELT measurements being significantly longer than the 1-min diagnostic threshold as defined by the International Society of Sexual Medicine (ISSM) for PE.20 This suggests participants are over-reporting the presence of PE and are not aware of the normative range of IELT and ejaculatory function. This is further reinforced by the participants reporting that they expected the normal IELT to be 16.5 ± 12.9 min (mean ± s.d.), with a median of 15 (95% CI: 15.6–17.4) min. These findings diverge significantly from the self-reported median of 5 min, which is more normative and congruent with the findings by Waldinger et al.2 Participants’ incorrect self-assessment of their PE, despite falling within the normal IELT range, along with the belief that a normal IELT exceeds the 90^th percentile, indicates a poor understanding of typical ejaculatory function and IELT. This also implies that men unrealistically expect longer intercourse to be the norm. However, PE diagnosis is multifactorial, and participants’ feelings of loss of control and distress were not explored in detail in this study.20,21 Therefore, it is possible that participants may have met the criteria for subclinical PE and were partially accurate in their self-assessment.

McMahon et al.22 conducted a cross-sectional study involving 4997 men across Australia and the Asia-Pacific region (China, Indonesia, Malaysia, New Zealand, the Philippines, South Korea, and Thailand) using a computer-assisted survey administered online or in-person, with methodology varying by location. This study assessed both ejaculatory and erectile function.

Regarding ejaculatory function and PE, McMahon et al.22 found that PE was under-reported by participants. Only 13% of participants self-reported having PE, despite approximately 31% of participants having PE according to the Premature Ejaculation Diagnostic Tool (PEDT) survey.23,24 This contrasts with the findings of Shaeer and Shaeer.17 Furthermore, of those who had PE according to the PEDT, 60% self-reported as not having PE. Participants failing to accurately self-report PE highlight an inaccurate perception or lack of understanding of normative ejaculatory function and IELT.

However, there may be some uncertainty in the diagnosis as 74% of participants with PEDT-diagnosed PE self-reported an IELT >2 min, which is above the diagnostic threshold for PE. This might suggest the presence of subclinical PE, as, unlike the study by Shaeer and Shaeer,17 this study incorporated all three dimensions of PE diagnosis, including feelings of loss of control and distress, which are included in the PEDT. Alternatively, as times were self-reported, social desirability and volunteer biases may have contributed to inflated times. There is evidence in the literature that suggests self-reported IELTs are often longer than stopwatch-measured IELT.24 Therefore, the self-reported IELT values may be inaccurate in the studies by Shaeer and Shaeer17 and McMahon et al.22 Ultimately, PE diagnosis in this study by McMahon et al.22 was supported by respondents with PEDT-PE qualitatively reporting low levels of sexual satisfaction and high levels of frustration regarding time to ejaculation as well as lack of control over ejaculation.

The study by McMahon et al.22 also indirectly assessed erectile function. It was found that 20% of participants were found to have mild-severe ED, as defined by the International Index of Erectile Function-5 (IIEF-5),25 according to a survey, but only 8% self-reported as having ED. Participants’ failure to accurately self-report the presence of ED implies a lack of information and possibly an inaccurate perception of normative erectile function.

McMahon et al.22 also found that there was comorbidity of PE and ED, as only 40% of participants with PEDT-diagnosed PE were confident in getting and keeping an erection. This may be a factor impeding accuracy in assessing perception and understanding of the individual conditions.

Wang et al.26 conducted a cross-sectional study in China involving 592 male participants that assessed ejaculatory function. Unlike the previous two studies,17,22 this study involved 466 participants with PE and 126 non-PE individuals who served as controls. All the participants completed a questionnaire and underwent a detailed assessment of their sexual function with a healthcare professional.

Unlike the study by Shaeer and Shaeer,17 Wang et al.26 found that participants with PE self-reported an IELT of 1.6 ± 1.3 min (mean ± s.d.) and a median of 1 min, which is more in keeping with the ISSM diagnostic criteria for PE. This is likely because the PE group was recruited from patients who presented with complaints of PE to the Department of Infertility and Sexual Medicine, and the inclusion criteria required a PEDT score greater than nine or an existing diagnosis of PE. In comparison, Shaeer and Shaeer17 randomly offered an online general survey.

However, similar to Shaeer and Shaeer,17 Wang et al.26 found that participants with PE had an inaccurate understanding of normal ejaculatory function. They expected “normal” IELT to be 14.0 ± 7.1 min (mean ± s.d.) with a median of 14 min, which is significantly greater than the more normative median of 5.4 min defined by Waldinger et al.2

Participants in the control group, who did not have PE, were recruited from individuals seeking reproductive counseling, undergoing health examinations, and healthy volunteers. Wang et al.26 found that the control group self-reported an IELT of 14.5 ± 6.7 min (mean ± s.d.), which participants perceived as “normal”. However, as times were self-reported and not recorded by a stopwatch, these values may be inflated due to social desirability bias. Regardless, the control participants’ perception of “normal” was significantly greater than the empirical findings by Waldinger et al.2 highlighting that they also had a poor understanding of “normal” ejaculatory function.

Furthermore, Wang et al.26 found that the mean expected IELT after treatment for PE in the PE and control groups was 15.4 ± 7.5 min and 19.1 ± 7.2 min (mean ± s.d.), respectively, indicating that participants anticipated better ejaculatory function and performance than what they consider “normal”. In addition, a strong positive correlation was found between perceived normal IELT and expected IELT after treatment in patients with PE, with a correlation coefficient of 0.844. This suggests that patients’ expectations of the outcomes of PE treatment are strongly influenced by their perception of “normal”. Therefore, an inaccurate understanding of “normal” can foster unrealistic expectations of PE treatment, which may negatively impact treatment satisfaction.

Takeuchi et al.27 performed a study assessing the erectile function of 66 men in Japan via self-administered surveys distributed at a suburban family medicine clinic.

Takeuchi et al.27 found that 92% of respondents met ED criteria of the IIEF-5, but only 39% self-reported having sexual dysfunction. These findings are similar to the study by McMahon et al.,22 again implying an inaccurate perception of normative erectile function.

Shabsigh et al.28 completed a study assessing the erectile function of 1053 men in the USA, where men were recruited for a men’s health study at the screening visit for a separate drug trial for sildenafil.

In the study by Shabsigh et al.,28 96% of participants who self-reported ED had IIEF scores indicative of ED. This suggests a highly accurate perception of normative and abnormal erectile function and a high degree of self-awareness. However, these patients were recruited from a cohort attending the clinic for a sildenafil drug trial. Thus, selection bias may have contributed to this accuracy, as they may already have some insight into their sexual dysfunction and may be seeking help through the trial. Shabsigh et al.28 also found that 36% of participants who self-reported “no ED” and 90% of participants who self-reported “unsure” about ED state had IIEF scores indicating positive ED status. Therefore, there is still some degree of uncertainty and inaccurate perception regarding normative erectile function, in concordance with the findings by McMahon et al.22 and Takeuchi et al.27

DISCUSSION

This review has revealed that there is limited research into men’s perception and understanding of normative sexual anatomy and function. Only seven relevant studies were identified in this review, which used a mixture of qualitative and quantitative methodology to assess men’s perception of normative penile length, ejaculatory function, and erectile function.

For penile length, it was found that there was an inaccurate perception of normal, with many men having a small penis self-perception despite being within the empirical range of normal. It was also found that men expected significantly longer than average penis lengths to be common.

The perception of normative ejaculatory function was assessed indirectly through understanding and awareness of PE. It was found that there was an inaccurate self-diagnosis of PE status, and men also expected significantly longer intercourse durations to be common. Thus, this implies an inaccurate perception of normative time to ejaculation.

Similarly, perception of normative erectile function was assessed indirectly through understanding and awareness of ED. Participants’ poor self-diagnosis of ED when compared against the IIEF-5, an empirical standardized survey, implies an inaccurate understanding of normative erectile function, as they have difficulty in distinguishing between “normal” and dysfunction.

Clinical implications

The implications of these findings are many. Firstly, a lack of understanding of normative penile length can lead to dissatisfaction and inaccurate self-perception of a small penis. This can contribute to the development of conditions such as small-penis syndrome,14 which is associated with significant anxiety and can negatively impact a patient’s personal relationships and significantly impair quality of life. Interestingly, Lever et al.13 found that 85% of women were satisfied with their partner’s penis size, whereas only 55% of men were satisfied with their size, and 45% of men wanted to be larger. Suggesting that female sexual satisfaction and positive relationship outcomes are less dependent on penile length than men assume. Furthermore, patients sometimes pursue surgical management to address this perceived deficiency, and King4 found that most men seeking penile lengthening surgery have normal-sized penises. Unfortunately, penile enhancement surgery can be associated with major disabling complications, including deformity and functional compromise. Even when successful, the outcomes are often suboptimal.29,30 Therefore, there are potential psychiatric, social, and surgical complications that can arise from a poor understanding of normal penile length.

Secondly, this review has shown that a poor understanding of normal sexual function, such as ejaculatory and erectile function, can also lead to inadequate awareness of sexual dysfunction. Patients in the studies included in this review were often unable to identify their own sexual dysfunctions accurately. This can be a barrier in seeking treatment for conditions such as ED and PE. ED can cause significant anxiety and difficulties in intimate relationships for men.5 ED and PE negatively impact the quality of life of both men and their partners. Therefore, identifying and treating these conditions is imperative, and this may be aided by a better understanding of what constitutes normal sexual function among the general male population.

Ultimately, the findings of this review suggest that education of clinicians and patients is required to address the inadequate understanding of normal sexual anatomy and function among the general male population. A recent systematic review found that counseling and patient education were often effective in convincing men who are worried about having a small penis that they are of normal size.30 Counseling can play an important role in both treating and improving diagnosis of sexual dysfunctions.5 As Wang et al.26 identified, unrealistic expectations of “normal” IELT are associated with unrealistic expectations for PE treatment outcomes, which contributed to treatment dissatisfaction and incompletion. Therefore, further education of clinicians, who can disseminate this knowledge amongst patients, may help correct misinformation. This would aid in improving self-perception and improving the diagnosis and management of sexual dysfunction. In exploring avenues for education, it may also be pertinent to investigate the sources of misinformation regarding sexual anatomy and function. Pornography is one potential source for misinformation for young men in the modern age.6,8 Sexual education of children and teenagers in school can also be variable and also absent in some political and cultural settings.9 There are likely multiple factors contributing to a lack of understanding of normative sexual anatomy and function. Identifying these sources of misinformation will be vital in guiding the development of patient-centered education programs to address this issue.

Further research is also required to identify effective methodologies for counseling and educating patients. Sexual health can be a sensitive topic and may not be acceptable discourse in particular political, cultural, or religious environments. Therefore, the ideal environment for counseling might include private settings such as General Practice (GP) clinics. Health professionals should approach such discussions in a non-judgmental manner, focusing on creating a safe and open environment to facilitate honest and culturally sensitive discourse. For physical aspects such as penile length, the use of anatomically correct models demonstrating realistic “normal” parameters for the appropriate population may help correct misinformation. Validated educational handouts, presented in simple language, may also help reinforce the knowledge. In places where sexual health education is provided in schools, this may be the ideal time point to provide counseling to prevent the development of inaccurate perceptions of “normal” in adolescents.

Implications for future research

This review has revealed that there is limited research into men’s perception of normative sexual anatomy and function. Further research is required to confirm and build upon these findings. Social desirability and volunteering biases, as well as confounding between PE and ED, were identified as the barriers to accurate research in this review.

Social desirability bias could lead to inflated and inaccurate measurements of values, such as penile length and IELT, in studies where participants self-measure or self-report values, as seen in the study by Shaeer and Shaeer.17 Volunteering bias can also lead to inaccuracies in studies where participants are not sampled randomly. For instance, a study by King4 found inaccuracies when comparing self-measured penile lengths with those measured by researchers. The study further elaborated that volunteer bias leads to men with larger penises being more likely to engage in such research. In addition, social desirability bias led to over-reporting of measurements to match masculine ideals.10,13 Therefore, it could be inferred that to optimize validity in future research, objective measurements taken by a researcher using a consistent technique should be considered. Furthermore, for ejaculatory function, there is evidence in the literature that suggests that self-reported IELTs are often longer than stopwatch-measured IELT.24 Therefore, the IELT values in the studies by Shaeer and Shaeer17 and McMahon et al.22 may be inaccurate. In future research, accuracy may be improved by using stopwatch-recorded IELT values.

To minimize social desirability and volunteer biases, primary research could be conducted through anonymously submitted surveys and, ideally, distributed randomly to men in clinical settings, such as GP clinics.

Another limitation of the study by Shaeer and Shaeer17 is that the functional and emotional outcomes of PE were not ascertained. Therefore, PE diagnosis is based solely on the IELT, which can be misleading. In future studies exploring PE, a validated questionnaire such as PEDT,23 as well as qualitative questioning regarding patient experiences, should be performed in conjunction with objective measures of IELT to achieve greater validity in diagnosis.

In the study by McMahon et al.,22 a significant proportion of participants with PE were found to have erectile difficulties. PE and ED may be comorbid in some men.31 This may be a confounding factor in assessing understanding of “normal” in ejaculatory and erectile function, as they may confuse symptoms between the conditions. For instance, some men may rush to ejaculate due to fear of losing their erection and subsequently perceive themselves to have PE rather than ED. Therefore, in future studies involving self-reports of PE or ED, it may be necessary to have participants describe their symptoms to assess the validity of their self-reports. Additionally, it may be pertinent to include participants with subclinical ED and PE in future research. While they may not meet the arbitrary criteria for formal ED and PE diagnosis, they may have significant dysfunction and will likely have an inaccurate perception of “normal”.

Limitations

Limiting the literature search to the English language may have resulted in relevant studies and evidence being overlooked. Therefore, future reviews on this topic should aim to search for relevant studies in other languages to identify any overlooked evidence.

Moreover, this review was limited to adult men only; therefore, the perspectives and level of understanding of normal sexual function or anatomy in adolescents have not been explored. Discovery of sexuality during adolescence may trigger concerns regarding sexual normality, and further research may help confirm this as well as identify sources of misinformation to address through patient-centered intervention. Psychological stress resulting from poor self-perception is likely to be greater during adolescence compared to adulthood; therefore, early intervention may lead to more favorable outcomes.

The included studies focused on exploring normality in the domains of penile length, ejaculatory function, and erectile function. Therefore, other aspects of sexual function and anatomy, such as libido or penile girth, have not been evaluated in this study. Research into these topics may also be similarly limited, and further research evaluating these topics may prove insightful.

Finally, regarding PE, most studies included in this review focused on IELT, which only represents outcomes in vaginal intercourse. Inclusion of other outcome measures of PE, such as anal, oral, and masturbation, in future research may improve the validity of PE assessment.

CONCLUSIONS

This review has revealed that there is limited research in the literature into men’s understanding of “normal” sexual anatomy and function. The findings of this review suggest that there may be an inaccurate understanding of what comprises “normal” in the domains of penile length, ejaculatory function, and erectile function. Further research is required to confirm these findings and potentially expand to assess awareness in other aspects of sexuality as well as in different cohorts, such as adolescents. Furthermore, research into sources of misinformation regarding sexual anatomy and function, such as pornography and cultural beliefs, may help guide education programs. There are potentially harmful sexual health, psychiatric, social, and surgical outcomes that may result from an inaccurate understanding of normal sexual anatomy and function. Ultimately, to improve sexual health, further sexual education of clinicians and the public may be necessary to combat misinformation and increase awareness of “normal”.

AUTHOR CONTRIBUTIONS

All authors have contributed significantly to the design of this narrative review. YF conducted the structured literature search, data extraction, analysis, and drafting of the manuscript. YF and WW edited the review. All authors contributed to the synthesis and discussions of the results. DK and KS were vital in the coordination of the project. All authors have read and approved the final manuscript.

COMPETING INTERESTS

All authors declare no competing interests.