Prolactin, oestrogen, and lipids in breast fluid.

Concentrations of prolactin, oestrogens, and lipids were measured in the plasma and breast-duct fluid of 8 non-lactating premenopausal women without a known history of breast disease. Concentrations of prolactin, oestrogen, and triglycerides were significantly higher in ductal fluid than in plasma, but there was little difference with cholesterol concentration. The high concentrations of prolactin and oestrogen found in the ductal fluid of Western women may be relevant to development of breast cancer.