Obesity is strongly associated with low testosterone and reduced penis growth during development

Context: Growth of male genitalia represents an important marker of sexual development. Testicle size is the primary measure and little is known regards penile length changes during puberty. Objective: This work aims to assess penis growth and testosterone levels in obese vs normal-weight children and adolescents, to evaluate a possible influence of obesity on genital development in boys, and to establish a new method for measuring penis length that allows comparison of normal-weight and overweight boys. Methods: We assessed anthropometric and genital development in 1130 boys from birth to age 20 years. Testosterone levels were also measured. A new method for penile length measurement was employed to minimize errors when comparing obese and nonobese children. Penis length was measured with a gentle, painless, straight positioning on a centimetric ruler without stretching, which is doable from the first years of life until the end of adolescence. Results: Penis length and testosterone are strongly related in children during puberty. Penile length growth is significantly decreased (by about 10%) in obese boys when compared to normal-weight boys, with concomitantly reduced testosterone levels, across puberal phases. Conclusion: Childhood obesity represents an important determinant of lower testosterone level and reduced penis development. A new method should be employed to improve penis measurement in normal-weight and overweight/obese boys. The possible significance of these observations for adult genital development and reproductive potential will require large longitudinal studies.