The Association between Estrogen Status and Other Biochemical Markers of Bone Turnover including Serum Galactosyl Hydroxylysine in Osteoporosis and Osteopenia

Osteoporosis is a chronic worldwide problem. It is a systemic skeletal disease characterized by low bone mass and structural deterioration of bone tissue leading to bone fragility. Cessation of ovarian function is the most widespread cause for osteoporosis in postmenopausal women. This study included 37womenaged 40 to 60 years. They were categorized into 3 groups according to their bone mineral density (BMD): Group I: 15 Normal control (T-score up to -1.5), Group II:12 Osteopenic women (T-score between– 1.5 to –2.5) and Group III:10 Osteoporotic women (T-score below– 2.5). For all subjects, dual energy X-ray absorptiometry (DEXA) was performed. Osteocalcin (OC),alkaline phosphatase (ALP), free galactosyl hydroxylysine (Gal-Hyl),calcium (Ca),inorganic phosphorus (P) and estradiol (E2)were measured in serum, whereas, deoxypyridinoline (Dpd) and creatinine levels in urine. Simultaneously both osteopenic and osteoporotic groups showed significant decreases in BMD when compared to the controls. Osteocalcin, ALP and Gal-Hyl showed significant increase (p<0.0001) among the osteopenic and osteoporotic groups versus the control group. Significant decrease in E2 levels were obvious among the osteopenic (p<0.0001) and osteoporotic (p<0.0001) women when judged against the controls. Urinary Dpd was significantly increased in the second and the third group (p<0.001) together. In osteoporotic group, significant negative correlations were observed between OC and BMD. Positive correlations were detected among the osteoporotic group between OC and ALP and between OC and Gal-Hyl. High significant negative correlations were confirmed between E2 and OC among both the osteopenic and the osteoporotic groups. Also, a significant negative correlation was established between E2 and Dpd in the osteoporotic group. In comparing between osteopenic and osteoporotic groups, significant decrease was recognized in BMD and significant increase was predicted regarding ALP, (p<0.05) Gal-Hyl (p<0.0001) and Dpd (p< 0.001). In conclusion, the decreasing level of E2 in early and post-menopausal women is the main cause of osteoporosis. Also, the measurement of serum Gal-Hyl may be of clinical value to identify groups at higher risk of osteoporosis and to predict bone loss.