- In addition to low BMD, amenorrheic (non-menstruating) athletes have impaired bone geometry and microarchitecture compared with regularly menstruating athletes and non-athletes.
- These are the first data to show abnormal bone geometry and microarchitecture in adolescent amenorrheic athletes.
- Later menarchal age was an important determinant of impaired geometry and microarchitecture.
Young amenorrheic (non-menstruating) athletes are known to have lower bone mineral density (BMD) compared to eumenorrheic (regularly menstruating) athletes. However, changes in BMD alone do not explain the increased fracture risk in amenorrheic athletes.
Research conducted at the Clinical Research Center of Massachusetts General Hospital showed that abnormal bone geometry and microarchitecture, independent determinants of fracture risk that had not been assessed in young athletes and nonathletes, are also impaired in young amenorrheic athletes.
Athleticism and Bone Health
The researchers focused on the bone health of young female athletes, knowing that adolescence and young adulthood are a critical time for bone acquisition, and excessive athleticism in young women is often coupled with irregular periods (in up to 24%). Whereas athletic activity is typically associated with higher BMD than seen in non-athletes, lack of periods (consistent with low estrogen levels) in certain overexercising athletes results in lower BMD than seen in normally menstruating athletes, with an increase in fracture risk. However, BMD alone does not explain the increased fracture risk in these women.
Abnormal bone geometry and microarchitecture can increase the risk of fracture even in those with normal BMD, as assessed by dual-energy x-ray absorptiometry (DXA). Understanding the impact of irregular or absent periods on bone geometry and microarchitecture could provide additional information regarding fracture risk in these women not provided by studies of BMD.
Published inThe Journal of Clinical Endocrinology & Metabolism, the study assessed both bone mineral density, bone geometry and microarchitecture in 50 subjects (16 amenorrheic athletes, 18 eumenorrheic athletes, and 16 nonathletes). “Athletes” were considered to be endurance athletes if they participated in at least 4 hours of weight-bearing exercise involving the legs, or ran at least 20 miles weekly for the preceding 6 months.
Following a complete history and physical examination, subjects’ bone age, body mass index, vitamin D levels, and BMD were measured, the latter using DXA. High-resolution peripheral quantitative computed tomography (HR-pQCT) was then used to measure volumetric bone mineral density, bone geometry and microarchitecture at the ultradistal radius (wrist) and distal tibia (shinbone).
Spine BMD scores were lower in amenorrheic athletes compared with eumenorrheic athletes and nonathletes. Neck and hip BMD were highest in eumenorrheic athletes, a benefit of athletic activity on bone not seen in amenorrheic athletes.
Bone Geometry and Microarchitecture: A Closer Look
In general, at the weight-bearing distal tibia, athletes had greater total and trabecular area than nonathletes. However, amenorrheic athletes had lower cortical area and thickness than the other two groups at this site. Further, trabecular number was lower, while trabecular separation was higher in amenorrheic athletes compared to eumenorrheic athletes and non-athletes. At the non-weight-bearing radius, trabecular density was lower in amenorrheic athletes compared to the other two groups.
The researchers noted that later menarchal age was an important determinant of impaired geometry and microarchitecture.
Therefore, the data indicated differences in the effect of athletic activity on cortical and trabecular parameters in young women at sites of weight-bearing and non-weight bearing bone depending on their menstrual status. This is the first time that the impact of athletic weight-bearing activity versus amenorrhea (and its associated estrogen deficiency) on bone geometry and microarchitecture in young athletes was demonstrated.
Limitations of the study include its cross-sectional nature and small sample size.
Funding: This work was supported by National Institutes of Health Grants 1 UL1 RR025758-01and 1 R01 HD060827-01A1.