Muscle function in Turner syndrome: normal force but decreased power

The Interplay between Muscular Grip Strength and Bone Mineral Density with Consideration of Metabolic and Endocrine Parameters in Individuals with Turner Syndrome

INTRODUCTION

Patients with Turner syndrome (TS) often face skeletal and muscular challenges, including reduced bone mineral density (BMD) and muscle weakness. This comprehensive study sheds light on the complex interplay between muscle strength, BMD, and metabolic and endocrine parameters in TS and healthy subjects.

METHODS

A cross-sectional study involving 42 TS patients and 70 healthy women was conducted. All patients had their BMD determined in the L1-L4 lumbar spine section and in the whole skeleton as well as the parameters of body fat mass (BF), and visceral fat mass (VF) were also determined. The maximum gripping force was measured with a hydraulic manual dynamometer. In addition, a number of blood hormonal and metabolic parameters were determined.

RESULTS

In the TS group, hand grip strength correlated positively with triglyceride levels but not with BMD. Healthy individuals had a positive link between hand grip strength and BMD, while patients with TS did not show a significant association between the two. A trend suggested that longer recombinant human growth hormone (rhGH) therapy might improve BMD in the L1-L4 region. Multiple linear regression analysis revealed that muscle strength assessment may be a potential exponent of reduced BMD, and also used clinically in young adult women but not in individuals with TS.

CONCLUSIONS

The relationship between BMD variables and hand grip might differ between the two groups, potentially indicating distinct musculoskeletal characteristics in TS patients. Longer rhGH therapy in TS patients may have a positive effect on BMD in the L1-L4 region. Understanding the intricate relationships between these factors is important for optimizing clinical management strategies and improving the quality of life for TS patients.

Musculoskeletal Health in Premature Ovarian Insufficiency. Part One: Muscle

Accelerated bone loss and muscle decline coexist in women with premature ovarian insufficiency (POI), but there are significant gaps in our understanding of musculoskeletal health in POI. This article is the first of a two-part review which describes estrogen signaling in muscle and its role in musculoskeletal health and disease. Current evidence regarding the utility of available diagnostic tests and therapeutic options is also discussed. A literature review from January 2000 to March 2020 was conducted to identify relevant studies. Women with POI experience significant deterioration in musculoskeletal health due to the loss of protective effects of estrogen. In addition to bone loss, muscle decay and dysfunction is now increasingly recognized. Nevertheless, there is a paucity of validated tools to assess muscle parameters. There is a growing need to acknowledge bone-muscle codependence to design new therapies which target both muscle and bone, resulting in improved physical performance and reduced morbidity and mortality. More high-quality research and international collaborations are needed to address the deficiencies in our understanding and management of musculoskeletal health in women with POI.

A 6-Year Follow-Up of Fracture Incidence and Volumetric Bone Mineral Density Development in Girls With Turner Syndrome

CONTEXT

Patients with Turner syndrome (TS) are at risk for osteoporotic fractures.

OBJECTIVE

The aims of this study were to assess the incidence of clinically important fractures in girls with TS and prospectively describe the development of volumetric bone mineral density (BMD).

DESIGN

Peripheral quantitative computerized tomography (pQCT) of the radius every other year over the 6 years of observation.

SETTING

Government-funded university referral center.

PARTICIPANTS

Thirty-two girls with TS, aged 6 to 16 years, were included in the analyses. Fracture incidence was compared with the data in the general population. Bone density and strength were compared with data from 185 healthy girls.

OUTCOMES

The main clinical outcome was the fracture occurrence. The secondary outcomes were the changes in Z-scores of the bone parameters.

RESULTS

Three girls with TS sustained four fractures during 6 years of observation. The fracture rate in TS was not substantially higher than the downward-biased fracture-rate estimate from age-matched, healthy controls (P = 0.48). Whereas the trabecular BMD Z-score decreased with age (β estimate -0.21 ± 0.04, P < 0.001), total bone cross-sectional area correspondingly increased (+0.16 ± 0.04, P < 0.001), which led to normal bone strength. A positive history of incident fractures was not significantly associated with any of the pQCT-derived bone parameters.

CONCLUSIONS

Current pediatric TS patients that are treated with growth hormone and estrogens are not at risk for osteoporotic fractures. Low BMD in TS may be counterweighted by enlarged bone radius, which leads to normal bone strength at the appendicular skeleton.

Health-related quality of life among children with Turner syndrome: controlled cross-sectional study

BACKGROUND

The aim of the study was to assess health-related quality of life (HR-QoL) in children with Turner syndrome in comparison with controls.

METHODS

We prospectively recruited 16 female girls with Turner syndrome (mean age 15.2±2.6 years) and 78 female controls (mean age 12.7±2.8 years) in randomly selected schools. We used the PedsQL, a generic HR-QoL questionnaire (self and parents' versions).

RESULTS

Global HR-QoL scores in Turner syndrome were lower than controls for self-reports (respectively, 74.3±3.0 vs. 82.8±1.3, p=0.01) and parents' reports (62.7±3.8 vs. 80.1±1.7, p<0.0001). In Turner syndrome, self-reported HR-QoL was impaired in school functioning (70.6±4.0 vs. 80.71±1.7, p=0.02), social functioning (78.2±4.0 vs. 90.4±1.8, p<0.01) and physical functioning (78.5±3.2 vs. 87.1±1.4, p=0.02), but not in emotional functioning. Parents' reported HR-QoL was impaired in all four dimensions.

CONCLUSIONS

HR-QoL was impaired in this cohort of young females with Turner syndrome, as in previously reported adult studies. In addition to medical treatment and routine clinical follow-up, female girls and teenagers with Turner syndrome should also be supported psychologically by social, educational and psychotherapeutic interventions that aim to address their self-esteem and emotional difficulties.

Cross-sectional study shows that impaired bone mineral status and metabolism are found in nonmosaic triple X syndrome

AIM

The effect of a supernumerary X chromosome on bones has not been reported, and this study evaluated bone mineral status and metabolism in nonmosaic triple X syndrome.

METHODS

This cross-sectional study comprised 19 girls, with a median age of 10.9 years, with nonmosaic triple X syndrome and a control group matched for age and body size. We studied ionised and total calcium, phosphate, parathyroid hormone (PTH), 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D, osteocalcin, bone alkaline phosphatase levels and urinary deoxypyridinoline concentrations. We also measured the phalangeal amplitude-dependent speed of sound (AD-SoS) and the bone transmission time (BTT) Z-scores.

RESULTS

Patients with nonmosaic triple X syndrome showed significantly reduced AD-SoS (p < 0.005) and BTT Z-scores (p < 0.0001) compared to the control group, and these results persisted when we divided the sample into prepubertal and pubertal patients (p < 0.05). These patients also had significantly reduced ionised calcium (p < 0.005) and 25(OH)D levels (p < 0.005) and higher phosphate (p < 0.0001) and PTH (p < 0.0001) levels.

CONCLUSION

Subjects with nonmosaic triple X syndrome exhibited a significant impairment in bone mineral status and metabolism similar to other X polisomy, such as Klinefelter's syndrome. This suggests the presence of a primary bone deficit and the need for regular and close monitoring of these subjects.

Bone Fragility in Turner Syndrome: Mechanisms and Prevention Strategies

Bone fragility is recognized as one of the major comorbidities in Turner syndrome (TS). The mechanisms underlying bone impairment in affected patients are not clearly elucidated, but estrogen deficiency and X-chromosomal abnormalities represent important factors. Moreover, although many girls with TS undergo recombinant growth hormone therapy to treat short stature, the efficacy of this treatment on bone mineral density is controversial. The present review will focus on bone fragility in subjects with TS, providing an overview on the pathogenic mechanisms and some prevention strategies.

The muscle-bone interaction in Turner syndrome

OBJECTIVES

Turner syndrome (TS) is associated with an increased fracture rate due to reduced bone strength, which is mainly determined by skeletal muscle force. This study aimed to assess the muscle force-bone strength relationship in TS and to compare it with that of healthy controls.

METHODS

This study included 39 girls with TS and 67 healthy control girls. Maximum muscle force (Fmax) was assessed through multiple one-legged hopping with jumping mechanography. Peripheral quantitative computerized tomography assessed the bone strength index at the tibial metaphysis (BSI 4) and the polar strength-strain index at the diaphysis (SSI polar 66). The effect of TS on the muscle-bone unit was tested using multiple linear regression.

RESULTS

TS had no impact on Fmax (p=0.14); however, a negative effect on bone strength (p<0.001 for BSI 4 and p<0.01 for SSI polar 66) was observed compared with healthy controls. Bone strength was lower in the TS group (by 18%, p<0.01, for BSI 4 and by 7%, p=0.027, for SSI polar 66), even after correcting for Fmax.

CONCLUSIONS

Similar muscle force induces lower bone strength in TS compared with healthy controls, which suggests altered bone-loading sensitivity in TS.