Comparison of mammary gland function during the ovulatory menstrual cycle and acute breast inflammation in women.

Abstract

SummaryStudies were undertaken to characterize the changes in the milk composition which occur 5–6 days before and 6–7 days after ovulation in lactating women. The composition of the milk at these times was compared to that from women with an acute inflammation (mastitis) in the breast to clarify the nature of the mechanism which caused the change in milk composition during the ovulatory menstrual cycle.The composition of breast milk taken from 2 women from days −8 to −3 and days 4 to 9, relative to the day of ovulation, showed significant (p < 0·05) increases in Na and Cl and a decrease in glucose. The concentration of albumin and total protein in the milk was unchanged. In contrast, the milk composition from 3 women who developed an inflammation in the one breast during lactational amenorrhea showed significant (p < 0·05) increases in the concentrations of Na, Cl, total protein and albumin in the milk from the affected breast as compared to the normal breast. The concentration of glucose was not significantly altered.The differences between the composition of milk during the menstrual cycle and during acute breast inflammation are exemplified by a further woman who developed an inflammation in the right breast only on day 7 after ovulation, which coincided with the post‐ovulatory change in milk composition. The concentration of albumin in the milk from the affected breast was significantly (p < 0·01) increased during the period of inflammation, while it remained stable in the milk from the normal breast. The other constituents showed the normal alterations associated with the luteal phase of the cycle.While the changes in the concentrations of the ions and albumin in the milk from the affected breast are consistent with the existence of a paracellular pathway between the cells, the changes during the menstrual cycle are not. It is suggested that the milk compositional changes which occur during the cycle are caused by a decrease in the mammary uptake of glucose, with a subsequent reduction in the synthetic activity of the gland.