Objectives: Because both breast cancer and the hormone leptin are associated with obesity and reproductive phenomena in women, we have examined whether there is a relationship between leptin and breast cancer among premenopausal and postmenopausal women. We have also evaluated in this dataset the association of IGF-I with breast cancer.
Methods: Seventy-five cases, diagnosed during mammographic screening, with incident breast cancer were matched for age and type of permanent residence with seventy-five controls from those screened negative in the same study base.
Results: There was no evidence for an association between IGF-I and either premenopausal or postmenopausal breast cancer risk or between leptin and postmenopausal breast cancer. Among premenopausal women, however, there was a strong and statistically significant inverse association of leptin with breast cancer.
Conclusion: We did not confirm the positive association, reported from other investigations, of IGF-I with premenopausal breast cancer risk. We have found evidence, however, that leptin may be inversely related to breast cancer risk among premenopausal women. The latter finding is not biologically implausible and deserves to be examined in additional datasets.