Natalia Cano Sokoloff

Fractures in Relation to Menstrual Status and Bone Parameters in Young Athletes.

INTRODUCTION This study was aimed to compare fracture prevalence in oligoamenorrheic athletes (AA), eumenorrheic athletes (EA), and nonathletes (NA) and determine relationships with bone density, structure, and strength estimates. METHODS One hundred seventy-five females (100 AA, 35 EA, and 40 NA) 14-25 yr old were studied. Lifetime fracture history was obtained through participant interviews. Areal bone mineral density (BMD) was assessed by DXA at the spine, hip, and whole body (WB). Bone structure was assessed by HRpQCT at the radius and tibia, and strength by finite element analysis. RESULTS AA, EA, and NA did not differ in age, sexual maturity, or height. AA had lower BMI, and older menarchal age than EA and NA (P ≤ 0.001). Bone mineral density Z-scores were lower in AA versus EA at the total hip, femoral neck, spine, and whole body (P ≤ 0.001). Lifetime fracture risk was higher in AA than EA and NA (47%, 25.7%, 12.5%; P ≤ 0.001), largely driven by stress fractures in AA versus EA and NA (32% vs 5.9% vs 0%). In AA, those who fractured had lower lumbar and WB BMD Z-scores, volumetric BMD (vBMD) of outer trabecular region in radius and tibia, and trabecular thickness of the radius (P ≤ 0.05). In AA, those who had two or more stress fractures had lower lumbar and WB BMD Z-scores, total cross-sectional area, trabecular vBMD, stiffness, and failure load at radius; and lower stiffness and failure load at tibia versus those with fewer than two stress fractures (P ≤ 0.05). CONCLUSION Weight-bearing athletic activity increases BMD but may increase stress fracture risk in those with menstrual dysfunction. Bone microarchitecture and strength differences are more pronounced in AA with multiple stress fractures. This is the first study to examine fractures in relation to bone structure in adolescent female athletes.

Altered trabecular bone morphology in adolescent and young adult athletes with menstrual dysfunction.

CONTEXT Young amenorrheic athletes (AA) have lower bone mineral density (BMD) and an increased prevalence of fracture compared with eumenorrheic athletes (EA) and non-athletes. Trabecular morphology is a determinant of skeletal strength and may contribute to fracture risk. OBJECTIVES To determine the variation in trabecular morphology among AA, EA, and non-athletes and to determine the association of trabecular morphology with fracture among AA. DESIGN AND SETTING A cross-sectional study performed at an academic clinical research center. PARTICIPANTS 161 girls and young women aged 14-26 years (97 AA, 32 EA, and 32 non-athletes). MAIN OUTCOME MEASURE We measured volumetric BMD (vBMD) and skeletal microarchitecture using high-resolution peripheral quantitative computed tomography. We evaluated trabecular morphology (plate-like vs. rod-like), orientation, and connectivity by individual trabecula segmentation. RESULTS At the non-weight-bearing distal radius, the groups did not differ for trabecular vBMD. However, plate-like trabecular bone volume fraction (pBV/TV) was lower in AA vs. EA (p=0.03), as were plate number (p=0.03) and connectivity (p=0.03). At the weight-bearing distal tibia, trabecular vBMD was higher in athletes vs. non-athletes (p=0.05 for AA and p=0.009 for EA vs. non-athletes, respectively). pBV/TV was higher in athletes vs. non-athletes (p=0.04 AA and p=0.005 EA vs. non-athletes), as were axially-aligned trabeculae, plate number, and connectivity. Among AA, those with a history of recurrent stress fracture had lower pBV/TV, axially-aligned trabeculae, plate number, plate thickness, and connectivity at the distal radius. CONCLUSIONS Trabecular morphology and alignment differ among AA, EA, and non-athletes. These differences may be associated with increased fracture risk.

Regional Fat Depots and their Relationship to Bone Density and Microarchitecture in Young Oligo-amenorrheic Athletes

CONTEXT Various fat depots have differential effects on bone. Visceral adipose tissue (VAT) is deleterious to bone, whereas subcutaneous adipose tissue (SAT) has positive effects. Also, marrow adipose tissue (MAT), a relatively newly recognized fat depot is inversely associated with bone mineral density (BMD). Bone mass in athletes depends on many factors including gonadal steroids and muscle mass. Exercise increases muscle mass and BMD, whereas, estrogen deficiency decreases BMD. Thus, the beneficial effects of weight-bearing exercise on areal and volumetric BMD (aBMD and vBMD) in regularly menstruating (eumenorrheic) athletes (EA) are attenuated in oligo-amenorrheic athletes (OA). Of note, data regarding VAT, SAT, MAT and regional muscle mass in OA compared with EA and non-athletes (C), and their impact on bone are lacking. METHODS We used (i) MRI to assess VAT and SAT at the L4 vertebra level, and cross-sectional muscle area (CSA) of the mid-thigh, (ii) 1H-MRS to assess MAT at L4, the proximal femoral metaphysis and mid-diaphysis, (iii) DXA to assess spine and hip aBMD, and (iv) HRpQCT to assess vBMD at the distal radius (non-weight-bearing bone) and tibia (weight-bearing bone) in 41 young women (20 OA, 10 EA and 11 C 18-25 years). All athletes engaged in weight-bearing sports for ≥ 4 h/week or ran ≥ 20 miles/week. MAIN OUTCOME MEASURES VAT, SAT and MAT at L4; CSA of the mid-thigh; MAT at the proximal femoral metaphysis and mid-diaphysis; aBMD, vBMD and bone microarchitecture. RESULTS Groups had comparable age, menarchal age, BMI, VAT, VAT/SAT and spine BMD Z-scores. EA had higher femoral neck BMD Z-scores than OA and C. Fat mass was lowest in OA. SAT was lowest in OA (p = 0.048); L4 MAT was higher in OA than EA (p = 0.03). We found inverse associations of (i) VAT/SAT with spine BMD Z-scores (r = -0.42, p = 0.01), (ii) L4 MAT with spine and hip BMD Z-scores (r = -0.44, p = 0.01; r = -0.36, p = 0.02), and vBMD of the radius and tibia (r = -0.49, p = 0.002; r = -0.41, p = 0.01), and (iii) diaphyseal and metaphyseal MAT with vBMD of the radius (r ≤ -0.42, p ≤ 0.01) and tibia (r ≤ -0.34, p ≤ 0.04). In a multivariate model including VAT/SAT, L4 MAT and thigh CSA, spine and hip BMD Z-scores were predicted inversely by L4 MAT and positively by thigh CSA, and total and cortical radius and total tibial vBMD were predicted inversely by L4 MAT. VAT/SAT did not predict radius or tibia total vBMD in this model, but inversely predicted spine BMD Z-scores. When L4 MAT was replaced with diaphyseal or metaphyseal MAT in the model, diaphyseal and metaphyseal MAT did not predict aBMD Z-scores, but diaphyseal MAT inversely predicted total vBMD of the radius and tibia. These results did not change after adding percent body fat to the model. CONCLUSIONS VAT/SAT is an inverse predictor of lumbar spine aBMD Z-scores, while L4 MAT is an independent inverse predictor of aBMD Z-scores at the spine and hip and vBMD measures at the distal tibia and radius in athletes and non-athletes. Diaphyseal MAT independently predicts vBMD measures of the distal tibia and radius.

Bone Accrual in Males with Autism Spectrum Disorder

Objective To test the hypothesis that bone accrual over a 4‐year period is reduced in boys with autism spectrum disorder (ASD) compared with typically developing controls. Study design Twenty‐five boys with ASD and 24 controls were assessed for bone outcomes. Fourteen boys with ASD and 11 controls were assessed both at baseline and after 4 years. The mean subject age was 11.0 ± 1.6 years at study initiation and 14.9 ± 1.6 years at follow‐up. Bone mineral density (BMD) was measured at the spine, hip, and whole body using dual‐energy X‐ray absorptiometry and normalized for age, race, and sex (BMD z‐scores). Height adjustments were performed as well. We assessed medical history, physical activity using questionnaires, vitamin D and calcium intake using food records, and serum calcium, phosphorus, 25(OH)‐vitamin D, and pubertal hormone levels. Results Boys with ASD had lower spine, hip, and whole body BMD z‐scores compared with controls. In those subjects assessed both at baseline and after 4 years, bone accrual rates did not differ between the 2 groups; however, spine and hip BMD z‐scores remained lower in the boys with ASD than in controls at follow‐up. Notably, the ASD group was less physically active at both time points. Conclusion Although pubertal bone accrual was similar to that in controls, BMD in children with ASD remained low over a 4‐year follow‐up period, suggesting that low BMD is a consequence of prepubertal factors, such as low physical activity. Studies are needed to investigate the causes and consequences of decreased BMD, to assess BMD in females and adults with ASD, and to evaluate therapeutic interventions.

Exercise, Training, and the Hypothalamic-Pituitary-Gonadal Axis in Men and Women

The hypothalamic-pituitary-gonadal (HPG) axis is essential for adequate responses to exercise and training both acutely and chronically. Both testosterone and estrogen play leading roles in neuromuscular adaptation to exercise in males and females. The purpose of this chapter is to illustrate the physiological and pathological changes that occur in the HPG axis secondary to exercise and training. In males, testosterone increases with acute bouts of exercise, but long-term effects are less clear, with evidence of lower testosterone in endurance athletes. Restricted energy availability may negatively affect hormone levels in male endurance athletes, but data regarding low energy availability and its impact on the HPG axis are limited in male athletes. Conversely, in females there is significant evidence that decreased energy availability inhibits the HPG axis, leading to menstrual irregularities and lower bone density. Hormonal changes secondary to acute bouts of exercise are more challenging to interpret in females due to menstrual variability, which traditionally has not been taken into account in many studies. However, some evidence supports an increase in testosterone and estradiol with acute exercise. More work is needed to elucidate the relationships among energy availability, basal hormonal fluctuations, and exercise, and their collective effects on the HPG axis.