Testicular responsiveness to hCG during infancy measured by salivary testosterone.

To investigate the role of gonadotropins in postnatal testicular activation, testosterone responsiveness to human chorionic gonadotropin was studied in 11 male infants (aged 5-180 days). The boys were given a single im injection of 5000 IU/1.7m2 hCG, and serum and salivary testosterone responses were then measured for 7 days. The results were compared with the serum testosterone responses of 8 older prepubertal boys (aged 1.7-10.4 years) studied with the same protocol. The mean (+/- SEM) basal serum testosterone levels were 2.67 +/- 1.27 nmol/l in the infants and 0.09 +/- 0.02 nmol/l in the prepubertal boys (p less than 0.05). Both groups gave a significant response to hCG stimulation (p less than 0.001, ANOVA, one-way). The stimulated concentrations of serum testosterone were higher in the infants than in the prepubertal boys (p less than 0.001). The mean basal level of salivary testosterone was 30.5 +/- 7.0 and the mean maximal level was 97 +/- 10.3 pmol/l in the infants (p less than 0.001). No age-related changes were observed in either basal or hCG-stimulated levels. In infants the mean (+/- SEM) maximal hCG-stimulated increase was 25 +/- 10-fold in serum and 8 +/- 4-fold in saliva (p = 0.13). A clear stimulatory effect of hCG on testicular testosterone production was found, suggesting that the postnatal increase in serum testosterone concentration in male infants is gonadotropin-mediated. Salivary testosterone concentrations can be increased by hCG, indicating that measurements of salivary testosterone may provide an optional, non-invasive method for assessing gonadal function in children.