Hormones in milk are a greater concern in conventional milk than in organic milk.
Many conventional (not organically raised) dairy cows are injected with hormones intended to increase their milk production.
In 2002, 22% of U.S. dairy cows were injected with recombinant bovine growth hormone (rBGH), also called recombinant bovine somatropin (rBST). Produced by genetically engineered E. coli, rBGH is similar to natural bovine growth hormone.
The hormone raises milk production in dairy cows but also gives them serious health problems, such as severe udder infections and crippling osteoporosis. The hormone is banned in the European Union, Canada, Australia, New Zealand, and Japan.
Milk from treated cows contains more pus, more antibiotic residue, more hormones, and more cancer-promoting IGF-1 hormone than milk from untreated cows.
Dairy cows raised organically are never treated with hormones.
The Institute for Responsible Technology: GM Hormones in Dairy