cross-sectional analysis of penile length in males 13 to 15 years old according to pubertal...
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Cross-Sectional Analysis of Penile Length in Males 13 to 15 Years
Old According to Pubertal Development Stages
Hasan Soydan,* Ilker Akyol, Ferhat Ates, Omer Yilmaz, Furkan Dursunand Kadir BaykalFrom the Urology Department, Haydarpasa Teaching Hospital, Gulhane Military Medical Academy, Uskudar, Istanbul, Turkey
Purpose: Genital development is affected by pubertal process to a great extent,and puberty is a complex phenomenon that is influenced by multiple factorsresulting in individual differences. We studied penile length and its relationshipto pubertal stage in boys 13 to 15 years old.Materials and Methods: Healthy boys who were candidates for military highschool were evaluated between June and July 2011. Age, residence and bodymass index were recorded. Stretched penile length was measured. Pubic hair wasassessed according to Tanner and Marshall staging. Genital puberty stage wasdefined by measurement of testicular volume with Prader orchidometer. Rela-tionship of penile length to age, residence, pubertal stages and body mass indexwas evaluated statistically.Results: A total of 1,539 boys were included in the study. Mean ages and numberof patients according to genital stage were as follows. Mean age was 14 years forgenital stage 1 (5 patients), 13.9 years (range 13 to 15) for stage 2 (194), 14.07years (13 to 15) for stage 3 (965) and 14.11 years (13 to 15) for stage 4 (375).Linear regression analysis revealed a significant effect of body mass index,genital stage and pubic hair stage on penile length (p �0.001) but no significanteffect of age or residence. Mean penile length was significantly different amongdifferent age groups and among pubertal stages. However, mean penile lengths ofdifferent age groups within the same pubertal stage were similar.Conclusions: Penile length during puberty should be evaluated individuallyaccording to the current pubertal stage. Our study offers a reliable reference tableof penile length for pubertal age group.
Abbreviations
and Acronyms
G � genital
GDS � genital developmentstage
PH � pubic hair
PL � penile length
Submitted for publication February 8, 2012.Study received institutional review board ap-
proval.* Correspondence: Urology Department, Haydar-
pasa Teaching Hospital, Gulhane Military MedicalAcademy, Uskudar, Istanbul, 34668 Turkey (tele-phone: 90-216-542-2000-4306; FAX: 90-216-348-7880; e-mail: [email protected]).
Key Words: penis, puberty, sexual development
MONITORING of genital development isa part of routine health care and canprovide clues to systemic disease. Nor-mal penile length in the prepubertalperiod is well defined. However, pe-nile length during puberty is some-what controversial, and good studieson the topic are lacking. Puberty is acomplex phenomenon that is influ-enced by multiple factors, and genitaldevelopment is greatly affected by the
pubertal process.0022-5347/12/1884-1319/0THE JOURNAL OF UROLOGY®
© 2012 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION AND RES
The onset of puberty may be differ-ent among individuals with similarlifestyles. Genetics, socioeconomic fac-tors, lifestyle, nutrition and ethnicitymay have roles in the onset and pro-gression of puberty.1 Generally testic-ular volume exceeding 3 ml indicatesthe onset of puberty. Testicular en-largement precedes rapid lengtheningof the penis. For this reason the crite-rion for onset of puberty depends on
testicular volume, not penile length.2http://dx.doi.org/10.1016/j.juro.2012.06.047Vol. 188, 1319-1323, October 2012
EARCH, INC. Printed in U.S.A.www.jurology.com 1319
PENILE LENGTH IN MALES 13 TO 15 YEARS OLD1320
Due to individual differences in pubertal develop-ment, it would be inaccurate to define normal PLaccording to age. Rather, it should be determinedwhether puberty has started at the appropriatetime, and then penile length should be assessed forcompatibility with pubertal stage.
Sexual development has been defined in previousstudies by stage.2–5 There are a number of studieson prepubertal and adult penile size.6–8 However,specific figures for the pubertal period are lacking.We studied PL and its relationship to pubertal stagein boys 13 to 15 years old. A secondary outcome ofthe study was determination of micropenis limitsaccording to age and pubertal stage.
MATERIALS AND METHODS
Boys who were candidates for military high school wereevaluated between June and July 2011. Institutional re-view board approval for the study was obtained. All pa-tients were healthy, with no apparent medical conditions.Age, height, weight and body mass index were recorded.Obese subjects and those with a history of metabolic syn-drome were excluded, and no further biochemical analysiswas performed.
Stretched PL (distance between symphysis pubis anddistal edge of glans penis) was measured. Pubic hairwas assessed according to Tanner and Marshall stag-ing.2,3 Genital puberty stage was defined by measure-ment of testicular volume with Prader orchidometer.Size of the larger testis was recorded whenever thevolumes of testes differed. Genital stage was definedaccording to testicular volume such that testicular vol-umes 1 to 3.9 cc, 4 to 11.9 cc, 12 to 20 cc and larger than20 cc were graded as stage 1, 2, 3 and 4, respectively.9 Atesticular volume of 4 cc was regarded as a marker forthe onset of puberty.2
Relationship of PL to age and pubertal stage was eval-uated using SPSS®, version 16.0 and MedCalc®, version10.2. The independent samples t test, Kruskal-Wallis testand Pearson correlation analysis were used to compare
Table 1. Mean penile lengths by age and genital stage
1
No. age (yrs):13 0 1114 5 17415 0 9
Mean � SD penile length (cm):*13 Yrs — 7.14 Yrs 6 � 0.68 8.15 Yrs — 8.
Total mean � SE penile length (95% CI)† 6.00 � 0.30 (5.14–6.85) 8.p Value — 0.Mean �2.5 SD penile length (cm) 4.8 3.
Mean penile length below 2 SD was 5.4 cm in patients 13 years, 6.4 cm in pat* p �0.001 among age groups.
† p � 0.0001 among G stages.the groups. Possible factors affecting PL were assessedwith linear regression analysis. A p value of less than 0.05was accepted as the threshold for statistical significance.
RESULTS
A total of 1,539 boys were evaluated. Of the patients52 (3.4%) were 13 years, 1,329 (86.2%) were 14 yearsand 158 (10.3%) were 15 years old (mean 14.05).Testicular development and pubic hair stage accord-ing to age group are shown in tables 1 and 2. Only 90boys (0.58%) were at PH stage 1. Mean ages andnumber of patients according to genital stage wereas follows. Mean age was 14 years for genital stage1 (5 patients), 13.9 years (range 13 to 15) for stage 2(194), 14.07 years (13 to 15) for stage 3 (965) and14.11 years (13 to 15) for stage 4 (375). Subjects werefrom all over the country, and all were white. Therewere no overweight subjects in terms of body massindex values. Significant positive correlation wasdetected between testis volume and Tanner PH stage(r � 0.751, p �0.001, see figure).
Table 1 demonstrates mean PL according to ageand G stage. Mean PL was significantly differentamong the age groups and G stages. However, PLs ofdifferent age groups within the same G stage weresimilar. Linear regression analysis revealed a sig-nificant effect of G stage and PH stage on PL(p �0.001) but no effect of age (p � 0.457). Meanpenile lengths according to age, genital stage andpubic hair stages are outlined in tables 1 and 2.
DISCUSSION
Puberty is a series of phenomena taking place in agiven period, and is staged according to pubic hairand genital growth as defined by Tanner and Mar-shall.2,3 Tanner staging performed by health careprofessionals has been suggested as the gold stan-
Genital Stage
2 3 4
31 10835 31599 50
19 11.23 � 1.24 12.09 � 0.7394 11.48 � 1.52 12.37 � 1.2502 11.77 � 1.49 12.46 � 1.2313 (8.00–8.54) 11.50 � 0.04 (11.41–11.60) 12.37 � 0.06 (12.25–12.50)
0.075 0.6517.7 9.3
years and 7.5 cm in patients 15 years old.
3 � 1.3 � 1.85 � 3.27 � 0.1534
ients 14
PENILE LENGTH IN MALES 13 TO 15 YEARS OLD 1321
dard compared to other scales.10 Genital stage 2,which is accepted as the beginning of puberty,11 isdetermined by testis volume, PL and scrotal skin.Others have suggested a testicular volume thresh-old of 3 ml to define the onset of puberty.12 In thisstudy we define G stage 2 as testis volume reaching4 ml.
Semiz et al reported the mean � SD ages of Gstages 2 and 5 as 12.81 � 1.0 years and 13.87 �0.98 years, respectively.5 Another study from Tur-key described mean � SD ages of 11.6 � 0.15 yearsand 12.2 � 0.16 years for G stage 2 and PH stage2, respectively, and 15.7 � 0.11 years for G stage5 and PH stage 5.13 Age range in our study was 13to 15 years (mean 14.05), with all patients but 5being at G stage 2 to 4 and all but 90 being at PHstage 2 to 4.
Table 2. Mean penile lengths by age and pubic hair stage
1 2
No. age (yrs):13 6 614 79 10715 5 4
Mean � SD penilelength (cm):*
13 Yrs 6.90 � 1.13 8.26 � 1.4014 Yrs 7.16 � 1.02 8.39 � 1.3215 Yrs 7.06 � 2.30 7.82 � 0.36
Total mean � SE penilelength (95% CI)
7.14 � 0.11 (6.91–7.37) 8.36 � 0.12 (8.12–8.60)
p Value 0.715 0.528Mean �2.5 SD penile
length (cm)4.365 5.095
* p �0.001 among age groups and among PH stages.
Pubic hair stages accordin
Race is another factor in pubertal developmentand PL.14 There are various reference tables fromdifferent countries in the literature covering thistopic.7,8 In the Turkish literature the beginning ofpuberty based on the appearance of pubic hairranges from 11.8 to 12.3 years.4,5 According to re-ports from different countries, G stages 2 and 3begin at ages 10.1 to 12.4 and 12.4 to 13.5 years,respectively, and PH stages 2 and 3 begin at 11.7 to12.7 and 13.2 to 14.1 years, respectively.1,15–19
Age at G stage 2 in our study was similar to thatsuggested in other studies. In a United States studyfull genital maturity was reached at 16 years in nonHispanic whites, 15 years in Mexican-Americansand 15.7 years in non Hispanic blacks.20 In a studyon penile size in Brazilian males mean � SD penilelengths were 8.6 � 1.2 cm at age 12, 10.1 � 1.2 cm
Pubic Hair Stage
3 4 5
13 16390 568
38 96
1.15 11.80 � 1.02 12.01 � 0.851.29 11.69 � 1.30 12.31 � 1.251.34 11.67 � 1.13 12.45 � 1.220.08 (10.36–10.72) 11.70 � 0.06 (11.57–11.81) 12.33 � 0.04 (12.23–12.41)
0.932 0.2728.475 9.23
11185
15
10.25 �10.53 �10.84 �10.54 �
0.5637.315
g to genital stages
PENILE LENGTH IN MALES 13 TO 15 YEARS OLD1322
at age 13 and 11.5 � 1.3 cm at age 14 years. How-ever, this study did not consider GDS or puberty.6
Similarly Marshall and Tanner reported PLs of 12.5to 14.5 cm at 12.5 years and 12.5 to 16.5 cm at 14.5years.3 In another study Schonfeld and Beebe re-ported mean � SD PL of 9.8 � 4.9 cm at 14 years.8
Finally, a study of 14-year-old Japanese boys showed amean � SD penile length of 8.3 � 0.8 cm.21 All pa-tients in our study were white.
It has been reported that there is no significantincrease in PL from age 0 to 5 years, with a slow rateof growth observed from 5 to 10 years and an in-creased rate from 11 to 18 years.6 This finding hasbeen corroborated by others.7,8 Reference tables forPL are necessary to demonstrate a possible devia-tion from normal growth since a short penis may bethe only sign of endocrinological pathology.
An apparently normal looking penis with a lengthbelow 2.5 SD of age matched counterparts is called amicropenis, and an endocrinological evaluation isindicated in boys with this condition.22–24 The deci-sion for endocrinological evaluation could be madejust by measuring the stretched PL and referring toan age based reference table during prepubertalages. However, our findings suggest that it is morecomplicated for pubertal boys. Mean � SD PLs weresignificantly different among age groups in ourstudy, being 10.56 � 2.077 cm (95% CI 9.98–11.14)at age 13 years, 11.26 � 1.96 cm (95% CI 11.15–11.36) at 14 years and 11.82 � 1.72 cm (95% CI11.55–12.09) at 15 years. Furthermore, we calcu-lated mean PLs and standard deviations accordingto genital development stage. When age and GDSwere evaluated together, there was a significant dif-ference among GDSs in the same age group andamong different age groups.
Micropenis limits, which were calculated usingour data, are outlined according to ages, G stagesand PH stages in tables 1 and 2. Micropenis limitwas smaller for boys at G stage 2 than those at Gstage 1. This finding required further analysis, aswe expected the opposite. In our study there wereonly 5 boys at G stage 1, and variation among thenumerical values (PLs) was small, whereas boys atG stage 2 had longer and smaller penises, whichproduced a larger SD, thereby decreasing the mi-cropenis limit even below that of the patients at Gstage 1. In fact, G stages 1 and 2 groups includedPH stages 1 and 2, which indicates that pubertyhad started in a sense in some subjects at G stage1, while it had not started in some at G stage 2.
Thus, genital staging might not be the optimalmethod to mark the onset and the initial stages ofpuberty. Conversely mean PLs within the sameage, including different PH stage groups, werestatistically different, while they were similarwithin the same PH stage including different agegroups, and a more coherent relationship of micro-penis limits with PH staging than with G stagingwas found (table 2).
It has been suggested that it would be more suit-able to accept testicular volume based PLs as nor-mals but not age based normals.7 Accordingly re-ported figures in the literature regarding PLs duringpuberty are relatively unreliable, which is why ourstudy was designed. It is clear that PL assessmentduring puberty should not be based on age, but apubertal staging method should be adopted as areference. Apparently our study population demon-strated more reliable results when PH staging wasused rather than genital staging in defining normalPLs and micropenis limits due to the small samplesize of patients at G stage 1. Another limitation ofour study is that our study population consistedmainly of 14-year-old boys, leaving a smaller role for13 and 15-year-old patients and recruits at a mili-tary academy in Turkey, which may in turn decreasethe power of our analysis. On the other hand, in arecent article by Tomova et al a uniformly distrib-uted large cohort of males was evaluated and largevariations of PL were detected within the same agegroups.25 Despite the fact that there is a discrepancywith our figures of mean PLs, their conclusion con-curs with ours in that there was great variabilitywithin the same age groups in their study. Thus,pubertal stage should be taken into account in de-fining normal penile lengths, rather than dependingsolely on age based tables.
CONCLUSIONS
Genital development during puberty is affected bymultiple factors and should be assessed individu-ally. PL is related to pubic hair and testicularvolume, which are signs of pubertal development.In our study mean PL was significantly differentamong different age groups and among pubertalstages. However, mean PLs of different age groupswithin the same pubertal stage were similar.Therefore, PL should be evaluated according tothe current pubertal stage individually, ratherthan depending solely on age based reference ta-bles. PL assessment based on PH staging might bemore appropriate in pubertal boys 13 to 15 years
old.
PENILE LENGTH IN MALES 13 TO 15 YEARS OLD 1323
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