A direct radioimmunoassay for free progesterone in saliva

The direct radioimmunoassay using iodinated tracer (125I-HIS-3CMO) has been developed for the determination of salivary progesterone of healthy volunteers with regular menstrual cycles. Lack of significant diurnal variation either in the follicular or luteal phase indicated that collections of saliva could be tailored to the need of individuals making the study somewhat easier. Salivary progesterone has shown to correlate significantly with free serum progesterone reflecting the unbound biologically active progesterone fraction in blood. Moreover, salivary progesterone concentration ranges are similar to those found in other studies. Our findings indicated that determination of progesterone in saliva could be used in place of serum or plasma. Since firstly, it is non-invasive, easy for sample collection and a stress-free technique. Secondly, it is much more accurate in prediction of corpus luteum function and ovulation than the basal-body temperature or endometrial biopsy or other clinical predictors currently in use. Finally, determination of daily salivary progesterone levels throughout the menstrual cycle may be advantageously employed as a non-invasive serial sampling technique for the assessment of corpus luteum and ovarian functions.