Saliva is a complex fluid, vital for oral health and digestion, composed of water, electrolytes, mucus, enzymes, antibacterial compounds, and various proteins. It plays a crucial role in food digestion, beginning with the enzymatic breakdown of food molecules. Saliva also serves as the body's first line of defense against pathogens, helps in wound healing, and facilitates taste and speech.
The human mouth contains three major salivary glands — the parotid, submandibular, and sublingual glands, each contributing uniquely to the composition of saliva. The parotid glands, located near the ears, primarily secrete watery saliva rich in enzymes like amylase, which is essential for starch digestion. The submandibular glands, found beneath the jaw, produce a mixed secretion of watery and mucous components, combining enzymatic activity with lubrication for swallowing. Lastly, the sublingual glands, under the tongue, mainly produce mucous saliva, contributing to the lubricative and protective functions of saliva.
Saliva is emerging as a source of biomarkers that can be collected without a needle. Saliva collection is simple, painless, and can be performed without specialized medical personnel, which makes repeated sampling practical outside a clinical setting.
Saliva contains a wide range of biomolecules, including hormones, antibodies, nucleic acids, and proteins, reflective of the body's physiological state. That makes it a workable medium for measuring how those values move over time.
Hormones enter saliva from the bloodstream through passive diffusion or active transport mechanisms. The permeability of salivary gland capillaries allows small, lipid-soluble hormones to diffuse directly. In contrast, larger or water-soluble hormones may require active transport to cross into salivary ducts. This is why saliva carries a signal of the body's physiological state.
For hormones, saliva has a distinct property: it carries the "free" (biologically active) fraction that is not bound to transport proteins, as much of the hormone in blood is. That fraction is closer to the hormone's functional level in the body than a total measurement is. The ease of collection also allows frequent sampling, so hormonal fluctuations can be followed over time.
The correlation between hormone levels in saliva and plasma is a key area of interest. Historically, blood has been the primary medium for hormone analysis due to its comprehensive representation of physiological states, so most of the scientific studies have focused on plasma concentrations. Understanding the correlation between hormone biomarker values in saliva and blood is thereby crucial for advancing the understanding of salivary hormones.
Research has shown that for certain hormones, such as cortisol, testosterone, and estradiol, salivary levels closely mirror the unbound, biologically active hormone concentrations in blood plasma. That correlation supports the use of saliva as an alternative medium for hormone analysis, and it is a less invasive option than a blood sample.
For research and wellness use only. Not for medical or diagnostic purposes.