Menstrual variations in thermal properties of the human breast

Menstrual variations in breast skin temperature (Tbr), heat flow (HF), volume (Vol), surface area (A), and core temperature (Tre) have been measured in 13 women. Measurements were made twice weekly on resting subjects throughout one cycle. Twelve of thirteen subjects showed increased Vol and A during the second half of the menstrual cycle; six also showed a minor peak prior to the midcycle rise in Tre. Eight of thirteen subjects had significant peaks in Tbr which preceded the estimated day of ovulation. Breast HF was generally low during the first half of the cycle, rising following estimated ovulation. Analysis of core-to-breast conductance indicates that a decrease in resistance to heat transfer occurs both during the luteal phase and at the Tbr peak. It is hypothesized that the control mechanism underlying the Tbr peak is independent of that controlling the postovulatory increases in Vol, HF, and Tre.