Assessment of testicular function by the radioimmunoassay of testosterone in saliva.

A sensitive RIA (500 fg/tube) has been developed for assay of testosterone in male saliva and extensively validated. In normal male saliva samples, morning concentrations (368 +/- 167 pmol/l) were significantly higher than evening samples (212 +/- 132 pmol/l). The circadian rhythm was confirmed by COSINOR analysis. Levels of testosterone in saliva, in response to HCG stimulation, accurately reflected the increase observed in matched plasma samples. Synacthen administration, although increasing circulating cortisol levels, caused no significant change in plasma and salivary testosterone concentrations. Prostatic cancer patients on diethylstilboestrol therapy had low salivary (47--122 pmol/l) and plasma (1.0--2.8 nmol/l) testosterone concentrations. Correct assessment of testicular function following stimulation and treatment regimens requires multiple sampling. Since saliva samples are easily collected by non-invasive techniques they represent an attractive alternative to plasma for evaluation of androgenicity.