Insulin-like growth factor I in pregnancy and maternal risk of breast cancer.
BACKGROUND
The role of insulin-like growth factor (IGF)-I in breast cancer remains controversial, despite numerous reports on the association of the hormone with breast cancer or high-risk mammographic densities. We hypothesized that exposure to elevated IGF-I during early pregnancy, a period characterized by intense cell proliferation in the breasts and in the presence of high concentrations of sex steroids, will be associated with increased maternal risk to develop a breast malignancy.


METHODS
The Northern Sweden Maternity Cohort is an ongoing prospective study, collecting blood samples from first-trimester-pregnant women since 1975 as part of screening for infectious diseases. A case-control study (212 cases and 369 controls) was nested among Northern Sweden Maternity Cohort members who delivered singleton babies. RIA was used to measure IGF-I and IGF-II levels. Conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI).


RESULTS
Breast cancer risk increased with increasing IGF-I (top tertile OR, 1.7; 95% CI, 1.1-2.7). The association was stronger among the primiparous (OR, 2.2; 95% CI, 1.1-4.4) than in the nonprimiparous women (OR, 1.4; 95% CI, 0.7-2.8). Upper-tertile risks seemed to decrease within the <28-, 28 to 33, and >33-year groups of age at sampling, from 2.5 (0.9-7.6) to 2.1 (0.9-5.0) and 1.2 (0.5-2.5), respectively. There was no association of breast cancer with first-trimester-pregnancy IGF-II.


CONCLUSIONS
The study offers further evidence that IGF-I is important in breast cancer. Our findings suggest that the adverse effect of IGF-I on the breast may be stronger before the remodeling of the gland induced by a first pregnancy.
Lukanova
Annekatrin
A
Division of Epidemiology, Department of Obstetrics and Gynecology, New York University School of Medicine, 550 First Avenue, NBV 9E2, New York, NY 10016, USA. lukana01@med.nyu.edu
Toniolo
Paolo
P
Zeleniuch-Jacquotte
Anne
A
Grankvist
Kjell
K
Wulff
Marianne
M
Arslan
Alan A
AA
Afanasyeva
Yelena
Y
Johansson
Robert
R
Lenner
Per
P
Hallmans
Göran
G
Wadell
Göran
G
Lundin
Eva
E
D000293:Adolescent; D000328:Adult; D001943:Breast Neoplasms / Q000097:blood / Q000453:epidemiology / Q000378:metabolism*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008327:Mammography; D010298:Parity; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood; D011446:Prospective Studies; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology
D007334:Insulin-Like Growth Factor I