Growth of the testes is usually the first sign of normal puberty in the male (see Fig. 13.4). In general, when the longitudinal axis of the testes (excluding the epididymis) is greater than 2.5cm, pubertal testicular enlargement has commenced. Most of the increase in size of the testes is due to seminiferous tubular enlargement since Leydig cell enlargement is minimal, even with active testosterone secretion.
The phallus is best measured when in a flaccid state and stretched, without including either the foreskin or the fat pad at the base of the phallus. Obesity increases the fat pad, so the penis may falsely appear to be abnormally short in an obese boy. The length of the stretched penis (excluding the foreskin) increases from an average of 6.2cm in the prepubertal state to 13.2cm in adulthood.
