The effect of growth hormone treatment on bone mineral density in prepubertal girls with Turner syndrome: a multicentre prospective clinical trial

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.

Skeletal Characteristics of Children and Adolescents with Turner Syndrome

Turner syndrome (TS) is a chromosomal disorder characterized by a short stature and gonadal dysgenesis, the latter of which requires estrogen replacement therapy (ERT) to induce and maintain secondary sexual characteristics. Insufficient ERT is associated with compromised skeletal health, including bone fragility, in adults with TS. In particular, estrogen insufficiency during adolescence is critical because the acquisition of a defective bone mass during this period results in impaired bone strength later in the life. In addition to bone mass, bone geometry is also a crucial factor influencing bone strength; therefore, a more detailed understanding of the skeletal characteristics of both bone mass and geometry during childhood and adolescence and their relationships with the estrogen status is needed to prevent compromised skeletal health during adulthood in TS. Although a delay in the initiation of ERT is associated with a lower bone mineral density during adulthood, limited information is currently available on the effects of ERT during adolescence on bone geometry. Herein, we summarize the current knowledge on skeletal characteristics in children and adolescents with TS and their relationships with estrogen sufficiency, and discuss the potential limitations of the current protocol for ERT during adolescence in order to achieve better skeletal health in adulthood.

Fracture rate in women with oestrogen deficiency - Comparison of Turner syndrome and premature ovarian insufficiency

OBJECTIVE

Women with early-onset oestrogen deficiency are at risk of reduced bone mineral density (BMD). We sought to assess fracture history and BMD in women with Turner syndrome (TS) and premature ovarian insufficiency (POI).

DESIGN

A cross-sectional observational study.

PATIENTS

Two hundred and sixty seven women with TS (median age 34.3 years) and 67 women with POI (median age 28.1 years).

MEASUREMENTS

A questionnaire was used to collect data on fracture history, co-morbidities and drug history including age at first oestrogen exposure. Clinical data included height, weight, serum vitamin D and hip and spine T-scores, which were adjusted for height and age. Fractures were subdivided into major osteoporotic fractures (MOF) and 'other' fracture types.

RESULTS

Overall fracture rate was similar in women with TS and POI (82 [30.5%] vs 22 [32.8%] respectively, P = .74). Compared to women with POI, those with TS had more fractures at MOF sites (30.2% vs 52.7%, P = .012) and fewer phalangeal fractures (27.9% vs 9.8%, P = .005). There was no difference in BMD between women who sustained a fracture compared to those who did not. Women with TS who fractured were more likely to suffer from hearing impairment compared to those with no fracture (62.2% vs 48.1%, P = .045).

CONCLUSIONS

TS is not associated with an overall excess risk of bone fracture. The higher rate of fractures at MOF sites in women with TS may be secondary to hearing impairment, thin cortical bone and abnormal bone remodelling.

Turner syndrome and osteoporosis

Turner syndrome is one of the most common sex chromosomal anomalies, characterized by the complete or partial loss of one X chromosome. Females with Turner syndrome are characterized by skeletal abnormalities, short stature and primary ovarian insufficiency. The aim of this narrative review was to identify the underlying mechanisms of osteoporosis in Turner syndrome, summarize its clinical manifestations and provide suggestions regarding the management of osteoporosis. Girls and women with Turner syndrome have lower bone mineral density and a higher fracture rate than healthy individuals. The most important risk factors for osteoporosis are inadequately treated primary ovarian insufficiency, followed by intrinsic bone abnormalities. Comorbidities that further increase the risk of osteoporosis include vitamin D deficiency, celiac disease and inflammatory bowel disease. In addition, hearing problems can predispose to falls. Early initiation of hormone replacement therapy (HRT) at the age of 11-13 years, prompt titration to the adult dose after 2 years and long-term follow-up to ensure compliance with HRT are the cornerstones of osteoporosis prevention in women with Turner syndrome.

Turner Syndrome: transition from childhood to adolescence

Transition from pediatric to adult care for young women with Turner Syndrome (TS) is characterized by high drop-out rates and inadequate follow-up, leading to increased morbidity and mortality. The complexity of the health issues young women with TS face or new problems that may arise warrants a well-structured and efficiently coordinated gradual transition plan, which is adapted to the individual needs of the emerging young adult and is based on interdisciplinary communication between physicians. In order to achieve a high level of care, it is important for the patient to be sincerely informed about her condition but also supported throughout this critical period of rising responsibility and autonomy by an experienced, multidisciplinary team. In this review, we present the basic concepts that should characterize transition and the major health issues that should be thoroughly addressed, including growth, Hormone Replacement Treatment and fertility options, cardiovascular disease, bone health, gastrointestinal disorders, autoimmunity, orthopaedic and ENT issues, as well as the overall psychological well-being of the young adult with TS.

Gradually increasing ethinyl estradiol for Turner syndrome may produce good final height but not ideal BMD

Estrogen replacement therapy in Turner syndrome should theoretically mimic the physiology of healthy girls. The objective of this study was to describe final height and bone mineral density (BMD) in a group of 17 Turner syndrome patients (group E) who started their ethinyl estradiol therapy with an ultra-low dosage (1-5 ng/kg/day) from 9.8-13.7 years. The subjects in group E had been treated with GH 0.35 mg/kg/week since the average age of 7.4 years. The 30 subjects in group L, one of the historical groups, were given comparable doses of GH, and conjugated estrogen 0.3125 mg/week ∼0.3125 mg/day was initiated at 12.2-18.7 years. The subjects in group S, the other historical group, were 21 patients who experienced breast development and menarche spontaneously. Final height (height gain < 2 cm/year) in group E was 152.4 ± 3.4 cm and the standard deviation (SD) was 2.02 ± 0.62 for Turner syndrome. The final height in group L was 148.5 ± 3.0 cm with a SD of 1.30 ± 0.55, which was significantly different from the values for group E. The volumetric BMD of group S (0.290 ± 0.026 g/cm³) was significantly different from that of group L or E (0.262 or 0.262 g/cm³ as a mean, respectively). This is the first study of patients with Turner syndrome where estrogen was administered initially in an ultra-low dose and then increased gradually. Our estrogen therapy in group E produced good final height but not ideal BMD.

Effects of Growth Hormone on Bone

PURPOSE

Describe the effects of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) on the skeleton.

FINDINGS

The GH and IGF-1 axis has pleiotropic effects on the skeleton throughout the lifespan by influencing bone formation and resorption. GH deficiency leads to decreased bone turnover, delayed statural growth in children, low bone mass, and increased fracture risk in adults. GH replacement improves adult stature in GH deficient children, increases bone mineral density (BMD) in adults, and helps to optimize peak bone acquisition in patients, during the transition from adolescence to adulthood, who have persistent GH deficiency. Observational studies suggest that GH replacement may mitigate the excessive fracture risk associated with GH deficiency. Acromegaly, a state of GH and IGF-1 excess, is associated with increased bone turnover and decreased BMD in the lumbar spine observed in some studies, particularly in patients with hypogonadism. In addition, patients with acromegaly appear to be at an increased risk of morphometric-vertebral fractures, especially in the presence of active disease or concurrent hypogonadism. GH therapy also has beneficial effects on statural growth in several conditions characterized by GH insensitivity, including chronic renal failure, Turner syndrome, Prader-Willi syndrome, postnatal growth delay in patients with intrauterine growth retardation who do not demonstrate catchup growth, idiopathic short stature, short stature homeobox-containing (SHOX) gene mutations, and Noonan syndrome.

SUMMARY

GH and IGF-1 have important roles in skeletal physiology, and GH has an important therapeutic role in both GH deficiency and insensitivity states.

Impact of Growth Hormone on Adult Bone Quality in Turner Syndrome: A HR-pQCT Study

Women with Turner syndrome (TS) are known to be at risk of osteoporosis. While childhood growth hormone (GH) treatment is common in TS, the impact of this therapy on bone health has been poorly understood. The objective of this study was to determine the influence of childhood GH treatment on adult bone quality in women with TS. 28 women aged 17-45 with confirmed TS (12 GH-treated) agreed to participate in this cross-sectional study. Dual X-ray absorptiometry (DXA) of lumbar spine, hip, and radius and high-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the radius and tibia were used to determine standard morphological and micro-architectural parameters of bone health. Finite element (FE) analysis and polar moment of inertia (pMOI) were used to estimate bone strength. GH-treated subjects were +7.4 cm taller (95% CI 2.5-12.3 cm, p = 0.005). DXA-determined areal BMD of hip, spine, and radius was similar between treatment groups. Both tibial and radial total bone areas were greater among GH-treated subjects (+20.4 and +21.2% respectively, p < 0.05), while other micro-architectural results were not different between groups. pMOI was significantly greater among GH-treated subjects (radius +35.0%, tibia +34.0%, p < 0.05). Childhood GH treatment compared to no treatment in TS was associated with an increased height, larger bones, and greater pMOI, while no significant difference in DXA-derived BMD, HR-pQCT micro-architectural parameters, or FE-estimated bone strength was detected. The higher pMOI and greater bone size may confer benefit for fracture reduction in these GH-treated patients.

Current concepts surrounding bone health and osteoporosis in Turner syndrome

Although Turner syndrome is the most common chromosomal disorder in women, a great deal remains to be understood in terms of optimal patient care, particularly as it relates to bone health. These women are known to be at risk for osteoporosis and fracture later in life as a result of a multitude of risk factors. While estrogen replacement and childhood growth hormone treatment are now considered standard of care, little is known of the role of further interventions to prevent and treat osteoporosis in these women. This review aims to highlight the specifics of bone health in Turner syndrome. We explore the bone diagnostic modalities and therapeutic interventions available and their role in the coming years of bone health management in this unique population.

Bone mineral density in Turner's syndrome and the influence of pubertal development

AIM

To describe bone mineral density at the lumbar spine in a group of girls with Turner's syndrome and determine its relation to pubertal development.

METHODS

Girls with Turner's syndrome aged over 12 years were invited to participate in the study. All participants underwent auxology, pubertal assessment and laboratory evaluation. Bone mineral density was estimated by dual-energy X-ray absorptiometry. Bone mineral apparent density was then calculated, and the results were compared with age-matched Dutch reference data.

RESULTS

We studied 32 girls with Turner's syndrome, mean (SD) [range] age 16.7 (2.6) [12.4-20.2] years and height 148.3 (9.0) [126-159.2] cm. Bone mineral apparent density lumbar spine values were -0.87 SD, significantly lower than in the reference population (p <0.001). Bone mineral apparent density values were positively and significantly associated with breast Tanner stages and postmenarcheal status, but not spontaneous puberty. However, no significant association was found between bone mineral apparent density and karyotype, growth hormone or timing of oestrogen therapy.

CONCLUSION

Girls with Turner's syndrome have lower bone mineral apparent density values at the lumbar spine, even after correcting for size, compared with an age- and sex-matched general population. Pubertal development has significant impact on bone mineral apparent density in girls with Turner's syndrome.

Effects of growth hormone and ultrasound on mandibular growth in rats: MicroCT and toxicity analyses

It has been shown by previous studies that mandibular growth can be enhanced by the systemic administration of recombinant growth hormone (rGH) and/or local application of therapeutic low intensity pulsed ultrasound (LIPUS). The purpose of this study was to determine if local injection of rGH and application of LIPUS to the temporomandibular joint (TMJ) would synergistically enhance mandibular growth. In an animal study, the effect of rGH, LIPUS, and combination of rGH and LIPUS on male Sprague-Dawley rats was observed. Mandibular growth was evaluated by measuring total hemimandibular and condylar bone volume and bone surface area as well as condylar bone mineral density (BMD) after 21 days on dissected rats' mandibles using micro-computed tomography (MicroCT). The expression of c-jun mRNA extracted from the liver of each of these rats was also quantified by real-time polymerase chain reaction to evaluate possible systemic effect of local rGH administration. Significant growth stimulation was observed in the mandibular and condylar bone of the animals treated with rGH, LIPUS, and rGH/LIPUS combined when compared with the control group. Bone volume, surface area, condylar bone mineral density, and c-jun expression were also compared between the treatment groups and the control in the liver. The results suggest that mandibular growth may be enhanced by injection of rGH or LIPUS application. The current study although showed synergetic effect of rGH and LIPUS application in increasing mandibular condylar head length, there was no significant changes in mandibular bone volume using both treatments together when compared to the two individual treatments. Moreover, combined rGH and LIPUS decreased condylar bone mineral density than each treatment separately. Future research could be directed to investigate the effects of different rGH doses and/or different LIPUS exposures parameters on lower jaw growth.

Association between ER-α polymorphisms and bone mineral density in patients with Turner syndrome subjected to estroprogestagen treatment--a pilot study

Reduced bone mineral density (BMD) is present in many women with Turner syndrome (TS), and hypo-estrogenism is known to play a vital role in bone mineralization disturbances. It has been suggested that genetic factors play an important role in the regulation of BMD. The aim of this study was to analyze the association between Pvu II and XbaI ER-α polymorphisms and BMD in TS patients subjected to estroprogestagen (EP) treatment. Thirty-two TS patients aged 17-38 (mean age 22.7 ± 8.2) along with 82 healthy controls were the subjects for this study. Baseline values of hormonal parameters, BMD and bone density markers were measured in the subjects. Subsequently, TS patients underwent 4 years of EP therapy. The results of laboratory parameters and BMD were analyzed in regard to PvuII and XbaI polymorphic variants of the ER-α gene. The increase in BMD of TS subjects was the highest in the 1st (7.5%, p = 0.013) and 2nd (6.6%, p = 0.008) years of treatment. Four years of EP therapy was reflected by a significant increase in BMD z-scores in patients with xx and Xx genotypes of the XbaI gene and in those with with the pp and Pp genotypes of PvuII. In patients with haplotypes other than XXPP, BMD z-scores were significantly higher compared to their baseline after 2 (p = 0.002), 3 (p < 0.001) and 4 (p < 0.001) years of treatment. In conclusion, genotypes xx and pp were shown to be prognostic markers of a good response to EP treatment, whereas the XXPP haplotype carriers were revealed to have the risk factors for insufficient responsiveness against EP treatment in BMD control.

Vitamin D receptor genotypes are associated with bone mass in patients with Turner syndrome

BACKGROUND

Turner syndrome (TS) patients present low bone mineral density (BMD) and increased fracture risk, probably due to a genetic defect aggravated by hormonal deficiency.

AIM

To study the relationship between vitamin D receptor (VDR) gene polymorphisms and BMD and bone parameters in TS patients.

METHODS

DNA from 65 TS patients and 110 controls was amplified by PCR and digested with FokI, BsmI and ApaI restrictases. Lumbar and femoral BMD were determined by DEXA and serum intact parathyroid hormone, osteocalcin and beta-CrossLaps by electrochemiluminescence.

RESULTS

Genotype distribution within the ApaI site was different in both groups: genotype Aa was more abundant in TS (63.8% vs. 41.3%; p<0.01), whereas AA predominated in controls (33.9% vs. 15.5%; p<0.01). Patients carrying genotype bb (BsmI) or ff (FokI) had lower BMD than those with other genotypes (p<0.01 and p<0.05, respectively).

CONCLUSION

BsmI and FokI polymorphic sites of VDR could be genetic determinants of BMD in TS patients.

Growth hormone and bone

PURPOSE OF REVIEW

Description of recent progress in our understanding of growth hormone (GH) effects on bone.

RECENT FINDINGS

Growth hormone deficiency is associated with low bone mass in children and adults, in addition to its well established impact on growth. Although GH and insulin-like growth factor I have direct skeletal actions, it is also possible that disordered parathyroid hormone secretion or effect may mediate some of the deleterious consequences of GH deficiency on bone. The benefits of GH replacement on bone mineral density have been demonstrated in many studies, but it remains unclear whether these are consistent across patient subgroups. The impact of GH replacement on fracture risk has not been definitively established. The positive effects of GH administration on growth are well established in childhood-onset growth hormone deficiency, as well as in several other pediatric conditions. Data on investigational uses of GH are also presented.

SUMMARY

GH may have a relevant role in bone physiology and several disease states in addition to growth hormone deficiency. Although the salutary effects of GH replacement on bone growth and bone density are well characterized, additional studies are required to examine the impact of GH replacement on fracture risk as well as potential benefits in osteoporosis.