Baseline serum estradiol and fracture reduction during treatment with hormone therapy: the Women's Health Initiative randomized trial.
BACKGROUND
The purpose of the study was to test the hypothesis that the reduction in fractures with hormone therapy (HT) is greater in women with lower estradiol levels.


METHODS
We conducted a nested case-control study within the Women's Health Initiative HT Trials. The sample included 231 hip fracture case-control pairs and a random sample of 519 all fracture case-control pairs. Cases and controls were matched for age, ethnicity, randomization date, fracture history, and hysterectomy status. Hormones were measured prior to randomization. Incident cases of fracture were identified over an average follow-up of 6.53 years.


RESULTS
There was no evidence that the effect of HT on fracture differed by baseline estradiol (E2) or sex hormone binding globulin (SHBG). Across all quartiles of E2 and SHBG, women randomized to HT had about a 50% lower risk of fracture, including hip fracture, compared to placebo.


CONCLUSIONS
The effect of HT on fracture reduction is independent of estradiol and SHBG levels.
Department of Epidemiology, University of Pittsburgh, Pittsburgh, PA 15261, USA. jcauley@edc.pitt.edu
J A
JA
Cauley
A Z
AZ
LaCroix
J A
JA
Robbins
J
J
Larson
R
R
Wallace
J
J
Wactawski-Wende
Z
Z
Chen
D C
DC
Bauer
S R
SR
Cummings
R
R
Jackson
D000368:Aged; D015415:Biomarkers / Q000097:blood; D004812:Epidemiologic Methods; D004958:Estradiol / Q000097:blood*; D015914:Estrogen Replacement Therapy; D005260:Female; D006620:Hip Fractures / Q000097:blood / Q000517:prevention & control; D006801:Humans; D007044:Hysterectomy; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000097:blood / Q000188:drug therapy; D058866:Osteoporotic Fractures / Q000097:blood / Q000517:prevention & control*; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D016896:Treatment Outcome
D015415:Biomarkers; D012738:Sex Hormone-Binding Globulin; D004958:Estradiol