Bone densitometry findings and prevalence of osteoporosis at initial scanning in girls with anorexia nervosa.

BACKGROUND AND

aimsLow bone mineral density (BMD) in children and young people (CYP) with anorexia nervosa (AN) is well recognized, yet the prevalence of osteoporosis remains unknown. This study investigates bone densitometry findings using dual energy X-ray absorptiometry (DXA) scan and peripheral quantitative computed tomography (pQCT) in girls with AN at initial referral, comparing outcomes by menstrual status and assessing osteoporosis prevalence.

methodsA retrospective review included 264 girls with AN, aged 10.2-19.8 years, referred for initial DXA and pQCT scans at a tertiary pediatric bone densitometry service between March 2013 and October 2022. Data on anthropometry; self-reported fracture history; pubertal status (normal, delayed, irregular menstruation, secondary amenorrhea, or unclassified); and densitometry parameters were collected. Osteoporosis was defined per the International Society for Clinical Densitometry (ISCD) as the presence of vertebral fractures (VF) or both a clinically significant fracture history (≥ 2 long bone fractures by age 10 or ≥ 3 by age 19) and BMD Z-score ≤ -2.0.

resultsThe cohort had a median age of 15.5 years, with 54.5% (n = 144) reporting secondary amenorrhea. Mean height SDS was 0.1 (1.0), while weight SDS [-0.8 (1.1)] and BMI SDS [-0.9 (1.1)] were significantly reduced (p < 0.001). Low BMD (lumbar spine bone mineral apparent density (BMAD) or total body less head BMD Z-score ≤ -2.0) was found in 18.9% (n = 50/264). Densitometry parameters were significantly lower than zero (p < 0.05), with greater deficits at trabecular-rich sites. BMD parameters, particularly total body less head BMD Z-score, were significantly better preserved in the secondary amenorrhea group compared to normal and delayed puberty groups (p < 0.05). pQCT showed reduced muscle (-2.4 [0.9]) and fat (-0.9 [1.0]) areas for height, with increased bone area for height (2.5 [1.4]). Long bone fractures were reported by 16.7% (n = 44), with 3% (n = 8) reporting two fractures. Mild single VFs were identified in 1% (n = 3), all meeting osteoporosis criteria due to VFs, with none having low BMD. No CYP met osteoporosis criteria based on fracture history and low BMD.

conclusionsGirls with AN exhibit significant bone density deficit at initial screening, particularly at trabecular sites, alongside reduced muscle and fat mass. However, osteoporosis as per current ISCD criteria is rare. Better skeletal health in the secondary amenorrhea group highlights the protective role of prior estrogen exposure.