Letters Section Editor: Robert M. Golub,
MD, Senior Editor.
To the Editor: It is possible that the results
of the WHI investigation1 may be explained
in part by the action of estrogen on biological factors that increase breast
cancer risk in postmenopausal women.2 Oral
estrogens, through their metabolic action, oppose insulin resistance. Furthermore,
through their hepatocellular actions, they cause an increase in sex hormone–binding
globulin level, and a decrease in insulin-like growth factor I (IGF-I) activity,
due to both a reduction in IGF-I level and an increase in IGF-binding protein-1
level.2 IGF-I is a potent mitogen for breast
tissue and breast cancer cells.
Campagnoli C, Abbà C, Ambroggio S, Peris C. Effects of Estrogen-Only Treatment in Postmenopausal Women. JAMA. 2004;292(6):683. doi:10.1001/jama.292.6.684-b