Low levels of Estradiol protect Bone Mineral Density in Healthy Young Postmenopausal Women

A. BAGUR; B. OLIVERI; M. BELOTTI; D. YANKELEVICH; F. SAYEGH

San Antonio

Congreso; XXIV Congreso Anual de la ASBMR; 2002

American Society for Bone and Mineral Research

Low levels of endogenous estrogens may play a role in the protection of bonemineral density (BMD) in healthy postmenopausal women (PMP). The aim ofthis study was to evaluate the role of total and bioavailable estradiol andtestosterone in the protection of BMD in healthy PMP. Ninety nine PMP womenaged 55 to 75 years were included. The BMD of L2-L4, Total Femur (TF) andTotal Skeleton (TS) was measured by DXA (Lunar Prodigy). Serum calcium,bone alkaline phosphatase (BAP), crosslaps (CTX), estradiol, estrona andtestosterone and urine calcium were measured. Estradiol was measured with asensitive assay that detects up to 5 pg/ml. Bioavailable sex hormones werecalculated. The population was divided in two groups: ¡Ü65 (Group 1) and >65years of age (Group 2). The general characteristics of the groups were (mean ¡ÀDS): weight 66 ¡À 11 vs. 65 ¡À 9 kg (ns), height 1.57 ¡À 5 vs. 1.52 ¡À 0.05 m(p<0.001), BMI 26 ¡À 4 vs. 27 ¡À 4 kg/m2 (ns), L2-L4 1.01 ¡À 0.16 vs. 0.95 ¡À 0.18g/cm2 (p<0.08, ns), TF 0.90 ¡À 0.11 vs. 0.82 ¡À 0.10 g/cm2 (p<0.001), TS 1.04 ¡À0.09 vs. 0.98 ¡À 0.07 g/cm2 (p<0.001).The Groups were also stratified according to estradiol levels: ¡Ü10 and >10pg/ml. The only significant differences in BMD were found in Group 1 in whichestradiol levels higher than 10 pg/ml protected BMD of L2-L4 (+14%, p<0.05)and TS (+3%, p<0.05). BAP and CTX tended to be lower in Group 1 with morethan 10 pg/ml of estradiol. The difference was close to reach statisticalsignificance (p<0.07 for both).The highest positive correlations were found in Group 1: estradiol correlatedwith L2-L4 (r=0.4, p<0.001), TF (r=0.3, p<0.004) and TS (r=0.4, p<0.001),bioavailable estrogen correlated with L2-L4 (r=0.4, p<0.003) and TS (r=0.4,p<0.001), testosterone correlated with L2-L4 (r=0.6, p<0.001), TF (r=0.4,p<0.01) and TS (r=0.6, p<0.001). CTX correlated negatively with estradiol andbioavailable estradiol (r=-0.3, p<0.01 and r=-0.3, p<0.006 respectively).In conclusion, estradiol levels higher than 10 pg/ml, testosterone andbioavailable estradiol are involved in the maintenance of BMD in healthypostmenopausal women under 65 years of age.