Salivary testosterone levels in preadolescent children

BACKGROUND: Saliva reflects the plasma free fraction of testosterone which is biologically active, and available for uptake by tissues. Testosterone concentration in saliva, though differing slightly from the concentration of unbound testosterone in serum, is in good correlation with the latter, indicating that salivary testosterone provides a reliable method for determination of serum free testosterone. The study aimed to investigate salivary testosterone levels and their changes in preadolescent children and to study sexual dimorphism. METHODS: Testosterone levels were determined in 203 healthy preadolescent children (77 girls and 126 boys) from saliva samples by radioimmunoassay. Sampling was performed once a year with respect to circadian and seasonal fluctuations of testosterone. Data were statistically analyzed by Statgraphic software. RESULTS: Mean salivary testosterone concentrations (± SD) were 0.038 ± 0.012 nmol/L and 0.046 ± 0.026 nmol/L for girls and boys, with the medians 0.035 nmol/L and 0.041 nmol/L, respectively. Statistical analysis did not prove changes in salivary testosterone concentrations in the preadolescent period of life, with an exception of the insignificant fall at the age of 7 years, and an insignificant rise at the age of 9 years in girls. CONCLUSIONS: Generally it can be concluded that salivary testosterone levels in our prepubertal subjects remained stable. There was no significant increase of salivary testosterone levels from the age of 6 until the age of 9 in both sexes. Sexual dimorphism in salivary testosterone levels was proved with significantly higher (p = 0.009) salivary testosterone levels in boys than in girls.