Variations in transforming growth factor beta in human milk are not related to levels in plasma

There is considerable variability in the concentrations of transforming growth factor beta (TGFbeta) in human milk from individual women which is not readily explained by maternal factors such as smoking or illness. A potential correlate is the maternal plasma level of TGFbeta since changes in plasma concentration of TGFbeta in response to a number of pathological conditions have been well documented. The purpose of this study was to investigate the relationship between the concentration of TGFbeta1 and TGFbeta2 in a single sample of human milk and plasma obtained on the same day from 80 lactating mothers at 5 weeks postpartum. The concentration of TGFbeta1 and TGFbeta2 in the aqueous fraction of human milk ranged from 228 to 3542 pg/ml (647, 438-799; median, 25th-75th percentiles) and 98 to 13 855 pg/ml (955, 535-1999) respectively and in paired samples of plasma from 440 to 19 460 (4026, 3245-6656) and 92 to 1739 (620, 391-925) respectively. Thus, in milk the median ratio of TGFbeta1 to TGFbeta2 was 1:1.6 whereas the corresponding median ratio in plasma was 7:1. There was no correlation between the concentration of either isoform of TGFbeta in milk and the corresponding TGFbeta in plasma.