Diet, serum, breast fluid growth hormone, and prolactin levels in normal premenopausal Finnish and American women

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Abstract
A food frequency questionnaire was used to estimate and compare the dietary fat and fiber consumption of 94 premenopausal women in Kuopio (rural Finland, where there is a relatively low risk of breast cancer) and 61 American women in New York (where there is a high risk of breast cancer). In keeping with previous reports concerning middle‐aged men, both groups had high fat intakes, but the Finnish women had considerably higher fiber intakes (24 ± 11 vs. 16 ± 6 g). Serum and breast fluid growth hormone and prolactin levels were compared in 29 of these American women and 24 of the Finnish women. All were healthy and had regular menstrual cycles. Serum growth hormone levels, which were measured by radioimmunoassay, were higher in the Finnish women; all but three of their breast fluids contained detectable growth hormone, frequently at extremely high concentration. In contrast, only 2 of the 29 breast fluids from American women had detectable amounts of growth hormone. Of the Finnish samples, 10 were also measured by an immunoradiometric assay with high specificity for the 22,000‐dalton growth hormone molecule; all but 3 had values less than 3.0 ng/ml. Serum and breast fluid prolactin concentrations, which were determined by radioimmunoassay, were no different in the two groups; both groups frequently had considerably higher levels in breast fluid compared with the corresponding serum. We postulated that dietary factors, perhaps related to fiber intake, affect the synthesis or posttranslational production of a growth hormone variant which may influence breast cancer risk.