The daily amounts of salivary
progesterone have been determined over the complete menstrual cycle for 9 normal women. The level of
progesterone during the follicular phase was about 150 pmol/l and increased significantly to about 350 pmol/l during the luteal phase of the menstrual cycle. The amounts of salivary
progesterone were significantly correlated with those in blood (P less than 0.001) in paired saliva-blood specimens taken from 96 women. Although these volunteers comprised patients with benign and malignant
breast disease and normal unaffected women, the relationship between salivary and blood
progesterone was similar for all groups. The concentration of non-
protein-bound
progesterone was determined using equilibrium dialysis. To correct for serum dilution the linear relationship between the percentage of
progesterone bound and the reciprocal of serum dilution has been exploited. The values of non-
protein-bound
progesterone obtained were significantly and linearly correlated with levels in saliva (r = 0.75, P less than 0.001, d.f. = 34) although the amount of free
progesterone in blood was about five times that found in saliva.