|dc.description.abstract||Introduction Obesity has been linked to increased risk of breast
cancer in postmenopausal women. Increased peripheral
production of estrogens has been regarded as the main cause
for this association, but other features of increased body fat
mass may also play a part. Leptin is a protein produced mainly
by adipose tissue and may represent a growth factor in cancer.
We examined the association between leptin plasma levels and
mammographic density, a biomarker for breast cancer risk.
Methods We included data from postmenopausal women aged
55 and older, who participated in a cross-sectional
mammography study in Tromsø, Norway. Mammograms, plasma
leptin measurements as well as information on anthropometric
and hormonal/reproductive factors were available from 967
women. We assessed mammographic density using a
previously validated computer-assisted method. Multiple linear
regression analysis was applied to investigate the association
between mammographic density and quartiles of plasma leptin
concentration. Because we hypothesized that the effect of leptin
on mammographic density could vary depending on the amount
of nondense or fat tissue in the breast, we also performed
analyses on plasma leptin levels and mammographic density
within tertiles of mammographic nondense area.
Results After adjusting for age, postmenopausal hormone use,
number of full-term pregnancies and age of first birth, there was
an inverse association between leptin and absolute
mammographic density (Ptrend = 0.001). When we additionally
adjusted for body mass index and mammographic nondense
area, no statistically significant association between plasma
leptin and mammographic density was found (Ptrend = 0.16).
Stratified analyses suggested that the association between
plasma leptin and mammographic density could differ with the
amount of nondense area of the mammogram, with the
strongest association between leptin and mammographic
absolute density in the stratum with the medium breast fat
content (Ptrend = 0.003, P for interaction = 0.05).
Conclusion We found no overall consistent association
between the plasma concentration of leptin and absolute
mammographic density. Although weak, there was some
suggestion that the association between leptin and
mammographic density could differ with the amount of fat tissue
in the breast.||en