PURPOSE: This study assessed the utility of dual-energy x-ray absorptiometry (DXA)-derived %fat Z-score and its relationship to the resumption of menses in female athletes. We have previously shown that a %fat Z-Score < -1.0 is associated with menstrual dysfunction in a cross-sectional cohort of female athletes. This study aimed to assess the relationship between change in %fat Z-Score < -1.0 and resumption of menses in amenorrheic female athletes (AMEN).

 

METHODS: This prospective cohort study assessed %fat Z-score in 44 AMEN (ages 15-30 years) who presented to a tertiary care hospital for bone health evaluation and underwent serial, clinical DXA scanning. 12 resumed menses (RESUME) and 32 remained amenorrhoeic (REMAIN). 

Athletes were grouped according to menstrual status and descriptive statistics were used to compare mean body mass index (BMI), percent expected body weight (%EBW), %fat Z-score, and other characteristics. Initial, final, and changes in %fat Z-score, %EBW, weight, and BMI of RESUME and REMAIN were compared using Wilcoxon rank-sum tests. We compared the initial and final proportion of athletes with low %EBW/BMI and low %fat Z-score using Fisher’s exact tests. Changes in the proportions of RESUME and REMAIN with low %EBW/BMI and low %fat Z-score were compared using an ordinal logistic regression, where the change in status was treated as an ordinal outcome. 

 

RESULTS: Mean age ± SD at baseline for the full cohort was 18.1 [KA1] ± 2.6. with no difference between RESUME AND REMAIN. 56.8% of athletes were runners and 15.9% dancers. There was no significant difference in baseline BMI (20.3 ±2.1 vs. 19.0 ± 1.6 kg/m²) or baseline %EBW (98.2% ± 8.6% vs. 91.0% ±5.9%) between RESUME and REMAIN. Average initial %fat Z-score was significantly higher in RESUME (-0.82) and was above the a priori %fat Z-score threshold of -1.0 compared to REMAIN (-1.55, p=0.023). RESUME had significantly higher mean final %fat Z-score (p=.015), %EBW (p=.0058), weight (p=.032) and BMI (p=.0011) than REMAIN (-0.62 vs. -1.38, 104.2% vs. 91.3%, 53.2 vs 51.0 kg, and 22.0 vs 20.0 kg/m², respectively). Additionally, significantly fewer RESUME had low BMI/%EBW (p=.0034) and low %fat Z-score (p=0.016) vs. REMAIN at the time of follow-up DXA (0% vs. 46.9% and 25.0% vs. 68.8%, respectively).

 

CONCLUSION: A %fat Z-score cut-off of -1.0 was a significant predictor of resumption of menses. Our results suggest that achieving a %fat Z-score >-1 may be a reasonable goal in clinical practice when treating female athletes with REDs and associated menstrual dysfunction. Future prospective research should investigate various body composition targets for menstrual function, as well as other mediating factors and underpinning mechanisms. 

 

DISCLOSURES: KEA serves as consultant for Hologic.