CHANGES IN THE CONCENTRATION OF CORTISOL IN MILK DURING DIFFERENT STAGES OF HUMAN LACTATION

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Abstract
A study was undertaken to determine by radioimmunoassay the changes in concentrations of cortisol in the mammary secretion of individual women during late pregnancy, lactogenesis established lactation and after cessation of breast-feeding. The concentration of cortisol In colostrum averaged 75% of that found in serum during late pregnancy. The concentration of cortisol (mean S.E.M.) was relatively high in the mammary secretions during late pregnancy (255 18 ng/ml) and decreased within 2 days after delivery (102 20 ng/ml) to reach low values by 10 days post partum (18 07 ng/ml.) During advanced lactation the cortisol values varied between 02 to 32 ng/ml but the mean concentration was significantly (p < 005) less (72 08 ng/ml. n = 75) than during late pregnancy, With the abrupt termination of breast-feeding, the concentration of cortisol generally increased above the values determined during established lactation, but, even during involution, the progressive changes in concentration varied markedly (range 05–400 ng/ml). The function of milk cortisol for the newborn is not known. However, it is possible that cortisol in breast milk may help lo control the transport of fluids and salts from the gastrointestinal tract of infants.