Effect of testosterone replacement after neonatal castration on craniofacial growth in rats

Neonatal castration precludes the pubertal increase in serum testosterone and reduces general and craniofacial growth in the male Wistar rat. This study aimed to determine whether exogenous testosterone given at an age beyond the normal pubertal peak restores general and craniofacial growth in male, neonatally castrated rats. The design was a randomized, double-controlled, cross-sectional trial. Male Wistar rats were assigned by weighted randomization to be either castrated early after birth (n = 35) or not (n = 15). On day 57, a 1.5-cm Silastic tube with testosterone was implanted in 18 of the castrated rats. On day 70 and day 110, body length, weight, and craniofacial growth were measured together with the weight of the prostate, and blood samples taken. The exogenous testosterone resulted in a significant increase in serum testosterone and prostate weight. All measures of general and craniofacial growth had higher mean values in the non-castrated control group than in the castrated group, while in the testosterone-implant group the mean values lay between these of the castrated animals and the non-castrated controls. Two-way ANOVA indicated a significant effect of the testosterone administration on lower-incisor growth and the size of the total skull vault.