title: Increase of free insulin-like growth factor-1 in normal human breast in vivo late in the menstrual cycle.
abstract: Prolonged exposure to endogenous and exogenous sex steroids increases the risk of breast cancer but the mechanisms are poorly understood. Increased levels of circulating insulin-like growth factor-1 (IGF-1) and low levels of IGF binding protein are associated with increased risk of breast cancer suggesting that IGF-1 has to be in its free form to be biologically active. Little is known about sex steroid regulation of IGF-1 locally in the breast. In this study microdialysis was used to determine the local levels of free IGF-1 in normal human breast tissue in healthy female volunteers during the menstrual cycle. The results showed that the extracellular levels of free IGF-1 locally in the breast were doubled in the luteal phase, when estradiol and progesterone levels were elevated, compared with the follicular phase. In plasma, free IGF-1 levels also exhibited a cyclic variation but to a less extent. The increased local levels of the free form of IGF-1 may promote proliferation in the breast epithelium. This could be important in sex steroid dependent breast cancer development.
authors.affiliation: Division of Gynecologic Oncology, University Hospital, Faculty of Health Sciences, Linköping, Sweden. lotda@imk.liu.se
authors.forename: Charlotta
authors.initials: C
authors.lastname: Dabrosin
mesh_terms: D000328:Adult; D001940:Breast / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008597:Menstrual Cycle; D017551:Microdialysis; D012016:Reference Values
chemical_list: D007334:Insulin-Like Growth Factor I