Bone Characteristics Among Female Endurance Athletes At Risk For Relative Energy Deficiency In Sport

PURPOSE: In this pilot study, we provide a comprehensive description of the bone microarchitecture and geometry of the tibia, bone mineral density (BMD), body composition, and free triiodothyronine (Free T3) among young female endurance athletes at risk of Relative Energy Deficiency in Sport (REDs). METHODS: We categorized female endurance athletes ages 18-30 years into REDs risk levels (green, yellow, orange, red) using the REDs Clinical Assessment Tool 2 through surveys, clinical lab assessments, bone density scans, and physician interviews. BMD was quantified using dual x-ray absorptiometry (DXA) at the femoral neck, total hip, lumbar spine, and whole body. Bone microarchitecture and geometry of the proximal and distal tibia were measured by high-resolution peripheral quantitative computed tomography (HR-pQCT). Results were analyzed using descriptive statistics. RESULTS: Eleven female participants (27 ± 3 years old, 1.66 ± 0.06 m height, 60.29 ± 4.17 kg weight) were stratified into three risk levels for REDs (green, n = 3; yellow, n = 7; orange, n = 1). Table 1 presents participant characteristics for each risk level, including BMD and distal and proximal tibia bone microarchitecture. Free T3 was within the reference range for all groups (2.0 - 4.4 pg/mL). Multiple bone measures for BMD, microarchitecture, and geometry were similar between green and yellow risk levels. BMD Z-score values were lower in the orange risk level for the whole body, femoral neck, total hip, lumbar spine. The same can be seen in total area, trabecular BMD, and cortical porosity of the distal tibia and cortical thickness of the proximal tibia for the orange risk level. CONCLUSIONS: Female endurance athletes with higher REDs risk levels appear to have poorer measures of bone microarchitecture, geometry, and BMD. This pilot study is underpowered to make more definitive conclusions. Table 1. - Descriptive Statistics. Metrics shown as mean + standard deviation. Green Risk (n = 3) Yellow Risk (n = 7) Orange Risk (n = 1) Whole body total Z-score - 0.1 ± 0.3 0.1 ± 0.9 - 1.4 Lumbar spine Z-score - 0.5 ± 0.3 - 0.4 ± ​​1.3 - 2.4 Total hip Z-score 0.4 ± 0.5 0.5 ± 1.3 - 1 Femoral Neck Z-score 0.6 ± 0.5 0.5 ± 1.4 - 1.2 Distal tibia - total area (mm2) 677.3 ± 85.4 690.8 ± 36.2 623.5 Distal tibia - trabecular BMD (g/cm3) 207.3 ± 17.7 213.2 ± 43.8 194.5 Distal tibia - cortical BMD (g/cm3) 931.6 ± 50.1 912.2 ± 27.5 961.1 Distal tibia - cortical thickness (mm) 1.352 ± 0.219 1.354 ± 0.196 1.274 Distal tibia - cortical porosity (%) 1.3 2.6 0.6 Proximal tibia - total area (mm2) 340.5 ± 21.6 335.7 ± 19.0 343.1 Proximal tibia - cortical BMD (g/cm3) 1019.7 ± 4.1 1050.7 ± 14.89 1036 Proximal tibia - cortical thickness (mm) 5.829 ± 0.259 6.020 ± 0.756 5.312 Proximal tibia - cortical porosity (%) .5 1.1 .7 Stanford Women's Health and Sex Differences Center Seed Grant