rBST In the section on rBST it states IGF 1 is a natural hormone found in the milk of both humans and cows causing the quick growth of infants I ve added a citation needed because this sentence seems to imply that the rapid growth of infants is due to the presence of IGF 1 in their milk This is not correct IGF 1 is produced endogenously in response to somatotropin and infants on formula IGF 1 free continue to grow rapidly See the Wikipedia entry Insulin like Growth Factor