By Kathryn E. Ackerman, Taraneh Nazem, Dorota Chapko, Melissa Russell, Nara Mendes, Alexander P. Taylor, Mary L. Bouxsein, and Madhusmita Misra in J Clin Endocrinol Metab, 2011.

In a recent cross-sectional study published in the Journal of Clinical Endocrinology and Metabolism, Ackerman and colleagues from Massachusetts General Hospital and Harvard Medical School examined the bone mineral density (BMD) and bone microarchitecture in 34 young (15-21yr) amenorrheic (AA) and eumenorrheic athletes (EA) compared to 16 age-matched nonathletes (NAC). BMD was measured using dual energy x-ray absorptiometry (DXA) and bone microarchitecture was determined using high-resolution peripheral quantitative computed tomography (pQCT). The purpose of the study was to determine whether impaired bone microarchitecture is an independent determinant of fracture risk in AA, which to date has not been evaluated. There were no significant differences between groups for chronological age, bone age, BMI, or vitamin D levels. Age of menarche did not differ between athletic groups, but was significantly higher in the AA compared to the NAC (14.2±2.5yr vs. 12.1±1.7yr, p=0.006). Lean body mass was significantly higher in the EA vs NAC (46.7±15.5kg vs. 39.8±4.5, p=0.009); whereas, percent body fat was significantly lower in AA vs. NAC (21.4±4.5% vs. 25.6±4.9%, p=0.03). Estradiol was significantly suppressed in AA to confirm amenorrheic status. The EA group demonstrated significantly greater femoral neck and hip BMD Z-scores (0.21±1.14 and 0.80±1.09 respectively); whereas, lumbar BMD and bone mineral apparent density (BMAD) Z-scores were higher in EA and NAC vs. AA (-0.62±1.05 vs. -0.36±1.26 vs. -1.66±1.10). Both athletic groups had significantly greater total area, trabecular area, and cortical perimeter at the tibia compared to NAC. Cortical density was lower in AA vs. NAC. After controlling for bone age, both athletic groups were significantly lower than NAC. Trabecular density was lower at the radius in AA compared to EA and NAC. Regression modeling demonstrated that later menarcheal age was an important determinant of impaired bone microarchitecture. After controlling for covariates, subject grouping explained 18-24% of the variance in tibial trabecular number and separation. In conclusion, amenorrhea was an important determinant of lower trabecular bone density of the radius, lower total density and greater trabecular separation at the tibia. Subject grouping explained the greatest amount of variance in trabecular number and separation at the tibia. Therefore, bone microarchitecture is a valuable bone health parameter to measure in amenorrheic athletes independent of bone mineral density and may represent important information relative fracture risk.