Radioimmunoassay of progesterone in saliva: application to the assessment of ovarian function.

We report a specific radioimmunoassay that has the required sensitivity (7 pg per assay tube) for determining progesterone concentrations in 400 microL of mixed saliva collected from normal women. The assay is precise: intra and inter-assay variation (CV) never exceeded 11.0 and 8.0%, respectively. The assay was used to determine progesterone in saliva samples collected daily for not less than 28 days by normal women and by patients having abnormal ovarian function. Four normal women provided matched saliva and plasma samples for accurate dating of the menstrual cycle by plasma progesterone, estradiol, lutropin, and follitropin. Nine further subjects collected saliva samples only, and from these data a provisional "normal range" was established. Progesterone concentrations in saliva during the follicular phase of the cycle were low (less than 100 pmol/L) but rose beginning on day 12 to reach peak values of 230-550 pmol/L on day 21. Thereafter, progesterone concentrations in saliva declined to values generally less than 170 pmol/L at the commencement of menses. Saliva samples from three patients attending an infertility clinic were also studied to assess ovarian function.