Relationship of volumetric bone density and structural parameters at different skeletal sites to sex steroid levels in women.
BACKGROUND
Although estrogen clearly plays a central role in regulating bone mass in women, studies in men have suggested that there may be a threshold bioavailable (bio) estradiol (E2) level below which aging men begin to lose bone and that the threshold for estrogen deficiency in cortical bone may be considerably lower than that in trabecular bone. There are no data testing this in women.


OBJECTIVE
Our objective was to assess volumetric bone mineral density (vBMD) and bone geometry by quantitative computed tomography and relate these to circulating bio E2 and bio testosterone levels.


METHODS
We studied a cross-sectional, age-stratified population sample of 235 women (age, 21-97 yr).


RESULTS
vBMD/structural parameters were not related to sex steroid levels in young premenopausal women (age, 20-39 yr) with a median bio E2 level of 17 pg/ml (63 pmol/liter). By contrast, bio E2 and bio testosterone levels were both significantly associated with trabecular and cortical vBMD and cortical area at multiple sites in late postmenopausal women (age > or = 60 yr) who had a median bio E2 level of 3 pg/ml (11 pmol/liter). Late premenopausal and early postmenopausal women (age, 40-59 yr) with an intermediate median bio E2 level of 11 pg/ml (42 pmol/liter) showed age-adjusted correlations of bio E2 levels with trabecular but not with cortical vBMD.


CONCLUSIONS
In women, bio E2 levels are associated with vBMD and some structural bone parameters at low but not high bio E2 levels. Similar to findings in men, the threshold for estrogen deficiency in cortical bone in women appears to be lower than that in trabecular bone.
Mayo Clinic, Endocrine Research Unit, 200 First Street SW, 5-194 Joseph, Rochester, Minnesota 55905, USA. khosla.sundeep@mayo.edu
Sundeep
S
Khosla
B Lawrence
BL
Riggs
Richard A
RA
Robb
Jon J
JJ
Camp
Sara J
SJ
Achenbach
Ann L
AL
Oberg
Peggy A
PA
Rouleau
L Joseph
LJ
Melton
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood / Q000378:metabolism; D015519:Bone Density; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D004958:Estradiol / Q000097:blood*; D005260:Female; D006801:Humans; D008875:Middle Aged; D013739:Testosterone / Q000097:blood*; D014057:Tomography, X-Ray Computed
D013739:Testosterone; D004958:Estradiol