Changes in trabecular bone score and bone density in female adolescents with anorexia nervosa: a longitudinal study

Catabolic to anabolic transition during nutritional rehabilitation of female adolescents with anorexia nervosa

Anorexia nervosa (AN) is associated with profound changes in glucose homeostasis, activity of the GH-IGF-1 axis, and adipose tissue, bone, and protein metabolism. We aimed to characterize the transition from a catabolic to anabolic state during the nutritional rehabilitation of female adolescent inpatients with AN. The study comprised 41 patients (aged 15.6 ± 1.6 yr). Blood samples were obtained at the time of admission and upon attainment of target weight. A subgroup of 18 patients also had blood samples obtained during the early refeeding period. Changes in body mass index (BMI) and BMI-SDS during hospitalization (5.1 ± 2.0 mo) were positively correlated with changes in markers of anabolism including IGF-1 (r = 0.424, P = 0.006), procollagen type I N-terminal propeptide (P1NP) (r = 0.375, P = 0.016), klotho (r = 0.468, P = 0.002), and alkaline phosphatase (ALP) (r = 0.051, P = 0.001) and were negatively correlated with the change in cortisol levels (r = -0.331, P = 0.035). Furthermore, changes in markers of anabolism were intercorrelated. IGF-1 increased consistently throughout the study period (P < 0.001); however, other variables showed a biphasic pattern. During the early refeeding period, there was a decrease in C-terminal telopeptides of type I collagen (CTX-1) (P < 0.001), uric acid (P < 0.001), cortisol (P = 0.056), fatty acid-binding protein 4 (FABP4) (P = 0.04), and klotho (P = 0.038) levels, whereas urea/creatinine ratio (UCR) (P = 0.045) increased. During the later phase, there was an increase in ALP (P = 0.039), insulin (P = 0.04), homeostatic model assessment for insulin resistance (HOMA-IR) (P = 0.06), and klotho levels (P = 0.02). In conclusion, the early refeeding period was characterized by a decrease in markers of catabolism, whereas the later phase was characterized by an increase in anabolic markers. We suggest that IGF-1, UCR, and klotho may be used as markers of reversal of catabolism and shift toward anabolism in patients with severe malnutrition.NEW & NOTEWORTHY We provide a comprehensive temporal characterization of changes in biochemical markers of glucose homeostasis, GH-IGF-1 axis activity, and adipose tissue, bone, and protein metabolism during refeeding of adolescents with anorexia nervosa. Although IGF-I levels increased continuously, other markers showed a biphasic pattern: an early decrease in catabolic markers, followed by an increase in anabolic markers later during hospitalization. IGF-1, urea/creatinine ratio, and klotho emerged as potential clinical biomarkers of catabolic to anabolic transition in patients with severe malnutrition.

Bone evaluation and relationship between body composition and bone mass in anorexia nervosa followed up by a multidisciplinary team

PURPOSE

Anorexia nervosa is a psychiatric disorder characterized by self-imposed fasting and significant weight loss, leading to nutrient deficiencies that disrupt bone metabolism. This cross-sectional observational study aimed to characterize the bone health of women with anorexia nervosa using dual-energy X-ray absorptiometry (DXA), trabecular bone score (TBS), and 3D shaper analysis.

METHODS

The study involved 12 women diagnosed with anorexia nervosa monitored by a multidisciplinary team and 11 control subjects. Both groups underwent blood sampling and assessments with DXA, TBS, and 3D shaper analysis.

RESULTS

The results indicated that areal bone mineral density (aBMD) and Z-scores at the total hip and femoral neck were significantly lower in the anorexia group compared to controls (p < 0.05). Additionally, the fat mass index was reduced in women with anorexia (p < 0.05). Appendicular lean mass index (ALMI) was similar between the two groups. 3D shaper analysis revealed that surface BMD (sBMD), volumetric BMD (vBMD), integral vBMD, and trabecular vBMD were generally lower in the anorexia group. Associations were found between proximal femur 3D parameters and total hip and femoral neck aBMD. Moreover, significant correlations were observed between total cortical vBMD, total cortical sBMD, integral vBMD, and TBS. ALMI was associated with total cortical thickness and showed a trend toward association with femoral neck Z-score.

CONCLUSION

In addition to previous studies indicating bone impairment in AN using DXA and TBS, the present study suggests that the 3D Shaper is also capable of detecting bone loss in this disorder. Therefore, the data encourage the further studies to assess the role of the 3D Shaper in prediction of fracture.

Trabecular Bone Score (TBS) Varies with Correction for Tissue Thickness Versus Body Mass Index: Implications When Using Pediatric Reference Norms

Trabecular bone score (TBS) derived from secondary analysis of lumbar spine dual-energy X-ray absorptiometry (DXA) scans improves fracture prediction independent of bone mineral density (BMD) in adults. The utility of TBS to assess fracture risk in younger patients has not been established because pediatric norms have been lacking. Robust TBS reference data from the Bone Mineral Density in Childhood Study (BMDCS) have been published. TBS values for the BMDCS study were derived using an algorithm that accounts for tissue thickness (TBS_TH ) rather than the commercially available algorithm that adjusts for body mass index (BMI; TBS_BMI ). We examined the magnitude of differences in TBS_TH and TBS_BMI in a cohort of 189 healthy youth. TBS values using both algorithms increased with age and pubertal development in a similar pattern. However, TBS_BMI values were systematically and significantly higher than TBS_TH (mean = 0.06, p < 0.0001). The difference between calculated TBS_BMI and TBS_TH was not uniform. Differences were greater at lower TBS values, in males, in older individuals, in those at later Tanner stages, and in those with a greater BMI Z-score. These systematic differences preclude the development of a simple formula to allow conversion of TBS_BMI to TBS_TH "equivalents." Because of these systematic differences in these two algorithms, using an individual's TBS_BMI to calculate a Z-score using the BMDCS TBS_TH reference values results in a falsely higher TBS Z-score (differences mean = 0.73, interquartile range [IQR] = 0.3 to 1.6). Until TBS_TH software for Hologic DXA equipment becomes commercially available, BMDCS TBS reference norms should not be used. © 2023 American Society for Bone and Mineral Research (ASBMR).

Update on trabecular bone score

Trabecular bone score (TBS) is an indirect and noninvasive measure of bone quality. A low TBS indicates degraded bone microarchitecture, predicts osteoporotic fracture, and is partially independent of clinical risk factors and bone mineral density (BMD). There is substantial evidence supporting the use of TBS to assess vertebral, hip, and major osteoporotic fracture risk in postmenopausal women, as well as to assess hip and major osteoporotic fracture risk in men aged > 50 years. TBS complements BMD information and can be used to adjust the FRAX (Fracture Risk Assessment) score to improve risk stratification. While TBS should not be used to monitor antiresorptive therapy, it may be potentially useful for monitoring anabolic therapy. There is also a growing body of evidence indicating that TBS is particularly useful as an adjunct to BMD for fracture risk assessment in conditions associated with increased fracture risk, such as type-2 diabetes, chronic corticosteroid excess, and other conditions wherein BMD readings are often misleading. The interference of abdominal soft tissue thickness (STT) on TBS should also be considered when interpreting these findings because image noise can impact TBS evaluation. A new TBS software version based on an algorithm that accounts for STT rather than BMI seems to correct this technical limitation and is under development. In this paper, we review the current state of TBS, its technical aspects, and its evolving role in the assessment and management of several clinical conditions.