Effects of raloxifene on circulating prolactin and estradiol levels in premenopausal women at high risk for developing breast cancer.
BACKGROUND
Prolactin is a peptide hormone necessary for normal breast development that may contribute to breast tumorigenesis. Estrogen is a significant positive regulator of prolactin synthesis; therefore, raloxifene, a selective estrogen receptor modulator under study as a breast cancer prevention agent, may modulate both estradiol and prolactin levels by inhibiting estradiol from binding to its receptor.


METHODS
Premenopausal women at increased risk for invasive breast cancer participated in a pilot chemoprevention trial and were given 60 mg raloxifene daily for 24 months. Fasting serum samples collected at baseline and after 12 months on drug were used to measure circulating prolactin, estradiol, and sex hormone binding globulin (SHBG) levels.


RESULTS
Of the 27 subjects who completed 12 months of raloxifene, 23 had paired prolactin samples, and 20 had paired estradiol and SHBG samples. Prolactin levels did not significantly change with raloxifene treatment, but SHBG levels increased (mean change = 7.3 nmol/L; P = 0.0001; 95% confidence interval, 3.9-10.7). Estradiol (mean change = 42 pg/mL; P = 0.048; 95% confidence interval, 1-84 pg/mL) levels were elevated when comparing 15 of the 20 women with paired estradiol measurements who also had both of these samples taken during the early follicular phase of the menstrual cycle.


CONCLUSIONS
This report is the first to examine the long-term effects of raloxifene on prolactin, estradiol, and SHBG levels in premenopausal women who are also at increased risk for developing invasive breast cancer. Raloxifene had no significant effect on prolactin levels but did increase estradiol and SHBG measurements.
Faupel-Badger
Jessica M
JM
Division of Cancer Prevention, National Cancer Institute, Bethesda, MD 20892-4254, USA. badgerje@mail.nih.gov
Prindiville
Sheila A
SA
Venzon
David
D
Vonderhaar
Barbara K
BK
Zujewski
Jo Anne
JA
Eng-Wong
Jennifer
J
D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis; D001943:Breast Neoplasms / Q000097:blood* / Q000188:drug therapy*; D018270:Carcinoma, Ductal, Breast / Q000097:blood / Q000188:drug therapy; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000097:blood / Q000188:drug therapy; D018275:Carcinoma, Lobular / Q000097:blood / Q000188:drug therapy; D004958:Estradiol / Q000097:blood*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000517:prevention & control; D010865:Pilot Projects; D017697:Premenopause; D011388:Prolactin / Q000097:blood*; D020849:Raloxifene Hydrochloride / Q000627:therapeutic use*; D012307:Risk Factors; D020845:Selective Estrogen Receptor Modulators / Q000627:therapeutic use*; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism
D014408:Biomarkers, Tumor; D020845:Selective Estrogen Receptor Modulators; D012738:Sex Hormone-Binding Globulin; D020849:Raloxifene Hydrochloride; D004958:Estradiol; D011388:Prolactin