Prolactin and breast skin temperature rhythms in postmenopausal women with primary breast cancer.

Plasma prolactin and cortisol were determined and breast skin temperatures measured in 8 postmenopausal diurnally active-nocturnally resting women, 7 with primary breast cancer and 1 with benign breast disease. In all subjects, prolactin peaked during the early morning hours. Cortisol and oral temperature served as internal physiological markers of anticipated rhythmicity in adrenocortical function and metabolism. In all patients studied, the tumour site had an increased mesor (midline-estimating statistic of rhythm) and reduced amplitude of the circadian breast skin temperature rhythm when compared to a similar site on the contralateral breast. Thermal asymmetry was also observed between left and right breasts. A cancer, if in the left breast, may reinforce lower amplitude and perhaps a higher mesor (associated with the healthy left breast in these particular patients), whereas if it is located in the right breast, it tends to nullify inter-mammary differences in mesor and amplitude. Screening for breast cancer appears to require subjects being monitored on at least two occasions before thermal abnormalities due to tumour or preneoplasia become discernible.