title: Measurement of estrogens in cow's milk, human milk, and dairy products.
abstract: Free natural estrogens in raw and commercial whole milk were quantitated by radioimmunoassay. The ranges of concentration of estrone, estradiol 17-beta, and estriol were 34 to 55, 4 to 14, and 9 to 31 pg/ml. Proportions of active estrogens (estrone and estradiol) in the fat phases of milk by radioactive tracer on separated milk were 80% and 65%. These findings were supported by radioimmunoassay of skim milk and butter. Equilibrium dialysis of skim milk with hydrogen 3 labeled estrogens showed that 84 to 85% of estrone and estradiol and 61 to 66% of estriol were protein bound. Whey proteins demonstrated a greater binding capacity than casein. This result was confirmed by radioimmunoassay of dry curd cottage cheese and whey. The concentrations in curd were 35, 11, and 6 pg/g. In whey they were 4, 2, and 3 pg/ml. The quantity of active estrogens in dairy products is too low to demonstrate biological activity. Butter was highest with concentrations of 539, 82, and 87 pg/g. Human colostrum demonstrated a maximum concentration of 4 to 5 ng/ml for estrone and estriol and about .5 ng/ml for estradiol. By the 5th day postpartum, they decreased to become similar to cow's milk.
mesh_terms: D000818:Animals; D002079:Butter / Q000032:analysis; D002417:Cattle; D002611:Cheese / Q000032:analysis; D003126:Colostrum / Q000032:analysis; D003611:Dairy Products / Q000032:analysis*; D004958:Estradiol / Q000032:analysis; D004964:Estriol / Q000032:analysis; D004967:Estrogens / Q000032:analysis*; D004970:Estrone / Q000032:analysis; D006801:Humans; D008892:Milk / Q000032:analysis*; D008895:Milk, Human / Q000032:analysis*; D011863:Radioimmunoassay / Q000379:methods
chemical_list: D004967:Estrogens; D004970:Estrone; D004958:Estradiol; D002079:Butter; D004964:Estriol