Serum prolactin levels are positively associated with mammographic density in postmenopausal women.
BACKGROUND
Prolactin is a polypeptide hormone that promotes normal breast proliferation and differentiation, but it is also implicated in the development and growth of mammary tumors. Mammographic density is a strong, independent predictor of breast cancer and, therefore, a potential surrogate indicator of breast cancer risk.


METHODS
To test the hypothesis that serum prolactin is positively related to mammographic density, we conducted a cross-sectional analysis of baseline data from the Postmenopausal Estrogen/Progestin Interventions (PEPI) Mammographic Density Study. Based on prior work, we further hypothesized that this association would be apparent only in women who had not recently used postmenopausal hormone therapy (HT).


RESULTS
In linear regression models adjusted for age, body mass index, race, smoking, alcohol use, parity and physical activity, among the 400 women who were not recent users of HT, prolactin was positively and statistically significantly associated with mammographic density (Beta log base 2 prolactin 0.0369 [95% CI: 0.0094-0.0645]. Thus, for each doubling of serum prolactin, there was an absolute increase in mammographic density of 3.69%. Additional adjustment for serum levels of estradiol, progesterone, sex hormone binding globulin and age at first pregnancy did not affect this result. There was no association between prolactin and mammographic density among the 169 participants who had recently used HT.


CONCLUSIONS
The correspondence between higher prolactin and higher mammographic density is consistent with prolactin's mitogenic properties and the associations between prolactin and breast tumor promotion. These results support the thesis that prolactin deserves investigation as a target for breast cancer risk reduction.
Greendale
Gail A
GA
Division of Geriatrics, David Geffen School of Medicine at UCLA, 10945 Le Conte Avenue, Suite 2339, Los Angeles, CA 90095-1687, USA. ggreenda@mednet.ucla.edu
Huang
Mei-Hua
MH
Ursin
Giske
G
Ingles
Sue
S
Stanczyk
Frank
F
Crandall
Carolyn
C
Laughlin
Gail A
GA
Barrett-Connor
Elizabeth
E
Karlamangla
Arun
A
D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D008327:Mammography; D008875:Middle Aged; D017698:Postmenopause / Q000097:blood* / Q000187:drug effects; D011388:Prolactin / Q000097:blood*
D011388:Prolactin