The luteal heat cycle of the breast in health.

Wearing a special thermometric brassiere, twenty-five normal women self-measured their breast surface temperature. The subjects averaged 39 years of age and all were parous. Observations were made for one hour each evening for one menstrual cycle under semi-standardized domestic conditions. They also collected daily samples of saliva for radioimmunoassay of progesterone concentration. The surface temperature of the breast is relatively cold around mid-cycle; thereafter, and without interruption in averaged data, the temperature increases steadily by about 1 degree C over the 12 days of the luteal phase; around the time of the menses, it falls rapidly. This heat rhythm does not occur in peri-menopausal low progesterone menstrual cycles or in patients where the breast tissue has been irradiated for cancer treatment.