SYMPOSIUM: HORMONAL REGULATION OF MILK SYNTHESIS Hormones, Mammary Growth, and Lactation: a 41-Year Perspective

摘要

When I was a beginning graduate student 41 yr ago it had been established that estrogen caused mammary duct growth; a combination of estrogen and progester- one was required for lobule-alveolar development of the mammary glands; and prolactin and growth hormone were essential for mammary growth. In laboratory spe- cies exogenous prolactin, glucocorticoids, and estrogen would initiate secretion of milk provided the mammary glands had a well-developed lobule-alveolar system. It was not known with certainty that progesterone inhib- ited the process. For some species, prolactin and thyrox- ine had been shown to stimulate lactation, while gluco- corticoids suppressed lactation. Definitive roles for growth hormone and insulin during lactation had not been established. Studies of hormonal control of mam- mary growth and function in cattle were few. In vitro methods to study hormonal regulation of the mammary glands were in their infancy. Quantitative measures of changes in mammary cell numbers and specific compo- nents of milk in response to hormones were rare. The concepts for quantification of hormone concentrations, hormone receptors, growth factors, and binding pro- teins in blood; hormonal regulation of nutrient parti- tioning; and hormonally induced mechanisms of action within mammary cells were waiting to be discovered. And eventually they were. However, lest we become too enamored with our current understanding of the hormones that control mammary growth and lactation, it remains a fact that the greatest physiological stimu- lus for milk yield is pregnancy, not some cocktail of exogenous hormones, growth factors, receptor agonists/ antagonists, or gene therapies. Viva la mom!