Progesterone in saliva does not parallel unbound progesterone in plasma

Area of Science:

• Endocrinology
• Biochemistry
• Reproductive Biology

Background:

• Extensive research exists on blood progesterone levels.
• Salivary progesterone is being explored as a non-invasive biomarker.
• Understanding the relationship between plasma and salivary progesterone is crucial for accurate interpretation.

Purpose of the Study:

• To compare plasma and salivary progesterone concentrations.
• To assess the correlation between salivary progesterone and non-protein-bound plasma progesterone.
• To evaluate the potential application of salivary progesterone measurements.

Main Methods:

• Paired plasma and saliva samples were collected.
• Progesterone concentrations in both matrices were measured.
• Progesterone binding to plasma and salivary proteins was investigated.

Main Results:

• Both plasma and salivary progesterone showed similar cyclical patterns, peaking in the latter half of the cycle.
• The ratio of plasma to salivary progesterone varied throughout the menstrual cycle.
• Salivary progesterone binding to salivary proteins remained constant, unlike plasma protein binding.

Conclusions:

• Salivary progesterone reflects overall cyclical changes similar to plasma progesterone.
• Saliva progesterone levels do not directly equate to free plasma progesterone due to salivary protein interactions.
• Interpretation of salivary progesterone data requires consideration of saliva-specific binding properties.