Aim: 

Salivary levels of steroid hormones have been shown to correlate to with the free "bioactive" fraction in plasma and are, thus, widely used in endocrine research. One potential source of bias is intraindividual variability. The aim of our study was to analyze infradian dynamics of salivary sex steroids in both sexes.

Methods: 

In two separate cohorts young healthy volunteers (17F & 45M; 18-25 years) were asked to collect saliva samples daily or every second day during a period of 30 or 75 days, respectively. Testosterone, estradiol and progesterone were measured in saliva samples by radioimmunoassay. Time series analysis was performed using repeated measures ANOVA and analysis of rhythmic variance (ANORVA).

Results: 

All analyzed hormones showed high intraindividual variability in both genders reaching coefficients of variation of more than 25%. In women the effects of menstrual cycle phases on salivary hormonal levels were confirmed. ANORVA showed no further cyclical components in any sex steroid. In men strong infradian rhythmic variations were found for testosterone (periods of 20 and 30 days) and estradiol (period of 12 days).

Conclusion: 

The relatively high intraindividual variability indicates the importance of infradian dynamics of salivary sex hormones. Our study shows that the widely used single time point samplings make the interpretation of salivary sex hormone levels difficult and its information value vague. The findings of infradian rhythms of sex hormones in men should be considered in endocrine research. Further studies are needed to uncover the causes and consequences of infradian hormonal rhythms in men.