ESPE Abstracts

Background: Reference values for penile length have not been established for Japanese boys.

Objective: We aimed to develop percentiles and means with standard deviations of stretched penile length (SPL) in Japanese boys.

Method: We conducted a cross-sectional study in 1 628 Japanese boys aged <9 years from 2007 through 2014. The LMS method was used to develop a growth reference and chart for SPL in boys aged 0–7 years. Inter-observer variation in the SPLs was assessed in 32 boys (median, 3 years of age; range, 0–11 years). The correlation between SPL and stature, weight, or BMI was analyzed by the Pearson’s test. The SPLs determined in the present study were compared with those of other ethnicities or those in previous Japanese studies.

Results: SPL increases continuously during prepubertal period, and most rapidly in the first 4 months of life. No significant fixed or proportional bias was found for inter-observer variation (P=0.5; r=0.33, P=0.06). There was no significant correlation between SPL z-score and stature z-score (r=0.14, P<0.001), weight z-score (r=0.09, P< 0.001), or BMI z-score (r=0.01, P=0.71). The SPL in current Japanese boys was significantly shorter than that in US Caucasian or Turkish boys, and longer than those reported by previous Japanese studies.

Conclusion: These data serve as an updated growth reference and chart for SPL in Japanese boys aged 0–7 years. SPL needs to be assessed by a growth reference for the same ethnicity and generation.

Funding: This work was supported by Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science, by Health Science Research Grant for Research on Applying Health Technology (Jitsuyoka (Nanbyo)-Ippan-014) from the Ministry of Health, Labor and Welfare, Japan, and by FGHR Clinical Research Grant.