Salivary hormone testing has been used in clinical and research settings for more than five decades and is recognized as a sensitive method for assessing hormone physiology. Unlike serum testing, which measures both protein-bound and unbound hormones, salivary testing reflects primarily the free, biologically active fraction of hormones. Numerous studies have demonstrated strong correlations between salivary hormone levels and the unbound fraction of hormones in serum and plasma, supporting saliva as a physiologically relevant matrix for hormone assessment.
In addition to reflecting bioavailable hormones, salivary testing offers important practical advantages. Hormone measurements in saliva are not influenced by variations in binding proteins, which can be affected by factors such as obesity, thyroid function, or medication use. Salivary samples are stable at room temperature and can be collected non-invasively at multiple time points throughout the day, making them especially well suited for evaluating hormones with circadian or cyclical patterns.