Assessment of the role of 17beta-oestradiol in bone metabolism in men: does the assay technique matter? The MINOS study.
OBJECTIVE
17Beta-oestradiol (17beta-E2), mainly its bioavailable fraction (bio-17beta-E2), is a determinant of bone mineral density (BMD) and bone remodelling in men. As direct measurement of bio-17beta-E2 is time-consuming, we compared the value of directly measured bio-17beta-E2 and of calculated bio-17beta-E2 and free 17beta-E2 by studying their association with BMD and markers of bone turnover in a cohort of men (MINOS).


METHODS
A cross-sectional study in which the association between BMD and bone markers, on the one hand, and serum levels of 17beta-E2, on the other, was analysed according to the levels of measured and calculated bio-17beta-E2 and free 17beta-E2 in a cohort of men.


METHODS
Men from the MINOS cohort including 87 men aged 19-45 to establish the reference control normal range of hormones and 637 men aged 50-85 (studied group).


METHODS
Total 17beta-E2, testosterone, SHBG and albumin were measured by standard methods. bio-17beta-E2 was directly measured after the precipitation of SHBG by ammonium sulfate. bio-17beta-E2 and free 17beta-E2 were calculated using serum SHBG and albumin levels as described by Sodegard et al. (J. Steroid Biochem., 16 (1982) 801).


RESULTS
Calculated bio-17beta-E2 and free 17beta-E2 were correlated with measured bio-17beta-E2 and between themselves (r = 0.90-1.00, P < 0.0001). Calculated bio-17beta-E2 and free 17beta-E2 disclosed a similar association with BMD (difference between lowest and highest quartiles of 17beta-E2: 2.6-6.8%, P < 0.05-0.005) to that of measured bio-17beta-E2 (3.6-6.1%, P < 0.005-0.001). The association between bone markers levels and measured vs. calculated 17beta-E2 were also similar. Predictive accuracy for lowered BMD and elevated levels of biochemical bone markers (evaluated using receiver operating characteristics) was relatively low (area under curve -0.582 to 0.709) but similar for different forms of bioavailable and free 17beta-E2.


CONCLUSIONS
In elderly men, the concentrations of bioavailable and free 17beta-E2, calculated using equations including either the measured albumin concentration or the constant albumin concentration of 43 g/l, can be used, at least in clinical studies, instead of the bio-17beta-E2 concentrations measured after ammonium sulfate precipitation.
Szulc
Pawel
P
INSERM Research Unit 403, Place d' Arsonval, Lyon, France. szulc@lyon.inserm.fr
Claustrat
Bruno
B
Munoz
Françoise
F
Marchand
François
F
Delmas
Pierre D
PD
D000293:Adolescent; D000328:Adult; D001682:Biological Availability; D015415:Biomarkers / Q000097:blood; D015519:Bone Density; D016723:Bone Remodeling; D001842:Bone and Bones / Q000378:metabolism*; D003430:Cross-Sectional Studies; D004958:Estradiol / Q000097:blood / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D012016:Reference Values; D012709:Serum Albumin / Q000032:analysis; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013739:Testosterone / Q000097:blood
D015415:Biomarkers; D012709:Serum Albumin; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone; D004958:Estradiol