Postnatal penile length and growth rate correlate to serum testosterone levels: a longitudinal study of 1962 normal boys
M Boas, KA Boisen, HE Virtanen… - European Journal of …, 2006 - academic.oup.com
M Boas, KA Boisen, HE Virtanen, M Kaleva, AM Suomi, IM Schmidt, IN Damgaard, CM Kai…
European Journal of Endocrinology, 2006•academic.oup.comObjective Infant boys show a brief activation of their hypothalamic–pituitary–gonadal axis
shortly after birth, the physiological significance of which is poorly understood. The objective
of the study was to investigate the correlation between endogenous testosterone levels and
penile size and growth. Design Prospective, longitudinal population-based study taking
place at two large primary obstetric centres at the University Hospitals of Copenhagen,
Denmark, and Turku, Finland. Methods Infant boys, 728 Danish and 1234 Finnish …
shortly after birth, the physiological significance of which is poorly understood. The objective
of the study was to investigate the correlation between endogenous testosterone levels and
penile size and growth. Design Prospective, longitudinal population-based study taking
place at two large primary obstetric centres at the University Hospitals of Copenhagen,
Denmark, and Turku, Finland. Methods Infant boys, 728 Danish and 1234 Finnish …
Objective
Infant boys show a brief activation of their hypothalamic–pituitary–gonadal axis shortly after birth, the physiological significance of which is poorly understood. The objective of the study was to investigate the correlation between endogenous testosterone levels and penile size and growth.
Design
Prospective, longitudinal population-based study taking place at two large primary obstetric centres at the University Hospitals of Copenhagen, Denmark, and Turku, Finland.
Methods
Infant boys, 728 Danish and 1234 Finnish, underwent clinical examinations at 0, 3, 18 and 36 months in Denmark and at 0, 3 and 18 months in Finland with blood samples taken at 3 months (n = 630). Penile length and growth were registered and reproductive hormones (testosterone, sex hormone binding globulin, oestradiol) were analysed.
Results
Penile length increased from birth (3.49±0.4 cm) to 3 years of age (4.53±0.51 cm) with the highest growth velocity from birth to 3 months (1.0 mm/month). Penile length and growth were significantly, positively correlated to serum testosterone (r = 0.31 and 0.076, P = 0.006 and 0.001 respectively) and to free testosterone index (r = 0.385 and 0.094, P = 0.0001 and 0.0001 respectively).
Conclusions
We found that endogenous testosterone was significantly associated with penile size and growth rate in infant boys. Thus, the postnatal surge in reproductive hormones appears to be important for genital growth. Our data may serve as an updated reference for normal penile length in Caucasian boys up to 3 years of age.
Oxford University Press