Salivary testosterone: a reliable approach to the diagnosis of male hypogonadism

Objective This study was to demonstrate that Sal-T is a reliable biomarker of androgen status in the diagnosis of male hypogonadism. Design In order to validate the salivary testosterone assay (Sal-T), its reproducibility, the agreement with serum free testosterone levels (Free-T), the correlation with other circulating androgen markers (bioavailable testosterone, total testosterone) and cut-off values were defined. Patients and methods We studied 52 eugonadic (E) and 20 hypogonadic (Hy) men. Sal-T was assayed using an adapted radioimmunoassay for serum testosterone. Sal-T concentrations were compared in nine cases before and after citric acid stimulation of salivary flow rate. Free-T and bioavailable testosterone (Bio-T) were calculated by Vermeulen equation and SHBG were determined by binding assay. Results Sal-T did not depend on salivary flow rate and morning samples from 07.00 h to 09.00 h were stable. Agreement between Sal-T and Free-T measurements was confirmed in all subjects. Sal-T levels correlated positively with all circulating androgens, showing the best correlation with Free-T in E (r = 0.92) as well as in Hy (r = 0.97). A cut-off value of Sal-T <= 0.195 nM showed 100% sensibility and specificity to rule out hypogonadism. Conclusions Our data showed that Sal-T is a reliable marker of testosterone bioavailability. The results support the inclusion of this biomarker as a noninvasive approach in the diagnosis of male androgen deficiency.