Osteoporotic hip and vertebral fractures in the Arab region: a systematic review

Asia is projected to account for the largest proportion of the rising burden of osteoporotic fractures worldwide. Data from the Middle East is scarce. We performed a systematic review on the epidemiology of vertebral and hip osteoporotic fractures in 22 Arab League countries, using Scopus, PubMed, and Embase. We identified 67 relevant publications, 28 on hip and 39 on vertebral fractures. The mean age of patients was 70-74 years, female to male ratio 1.2:2.1. Age-standardized incidence rates, to the UN 2010 population, were 236 to 290/100,000 for women from Kuwait and Lebanon, lower in Morocco. Risk factors for hip fractures included lower BMD or BMI, taller stature, anxiolytics, and sleeping pills. Most patients were not tested nor treated. Mortality derived from retrospective studies ranged between 10 and 20% at 1 year, and between 25 and 30% at 2-3 years. Among 39 studies on vertebral fractures, 18 described prevalence of morphometric fractures. Excluding grade 1 fractures, 13.3-20.2% of women, mean age 58-74 years, had prevalent vertebral fractures, as did 10-14% of men, mean age 62-74 years. Risk factors included age, gender, smoking, multiparity, years since menopause, low BMD, bone markers, high sclerostin, low IgF1, hypovitaminosis D, abdominal aortic calcification score, and VDR polymorphisms. Vertebral fracture incidence in women from Saudi Arabia, mean age 61, was 6.2% at 5 years, including grade 1 fractures. Prospective population-based fracture registries, prevalence studies, predictive models, fracture outcomes, and fracture liaison services from Arab countries are still lacking today. They are the pillars to closing the care gap of this morbid disease.

Disease burden of osteoporosis and other non-communicable diseases in Lebanon

Osteoporosis is more common than most feared non-communicable diseases in the Middle East. This justifies the need to place osteoporosis as a health priority in the region.

INTRODUCTION

Osteoporosis is a common disease associated with severe debilitating consequences. The objective of this study is To evaluate and compare disease burden from osteoporosis and other non-communicable diseases (NCDs) in Lebanon.

METHODS

We assessed the prevalence of osteoporosis and other NCDs, such as obesity, diabetes, hypertension, dyslipidemia, and cardiovascular diseases, based on a published population-based study of Lebanese ≥ 65 years. We compared incidence rates of hip fractures and major osteoporotic fractures (MOF) (spine, hip, humerus, and forearm) to the five commonest cancers in women ≥ 50 years. Rates were based on the national hip fracture and cancer registry data, provided by the Lebanese Ministry of Public Health. MOF incidence rates were derived from national hip fracture incidence rates and MOF/hip fractures incidence rate ratios from the literature.

RESULTS

Over 70% of elderly Lebanese had osteoporosis defined by densitometric criteria or prevalent morphometric vertebral fractures. This by far exceeded the prevalence of other NCDs, such as hypertension (53%), diabetes (21%), dyslipidemia (31%), and cardiovascular diseases (30%). Morphometric vertebral fractures (grades 2 and 3) were present in 19% of women and 12% of men. The incidence rates for MOF were 1.6 times greater than those for breast cancer, and 7.4-9.9 folds higher than those for the next commonest cancers of the lungs, colon, and ovaries. Hip fracture incidence rates were lower than those of breast cancer but were 2.1-2.8 folds higher than those of the above-mentioned cancers.

CONCLUSION

This first of its kind study in the Middle East demonstrates that osteoporosis is a common disease, more common than most feared NCDs. Our findings are comparable to those in western populations and justify placing osteoporosis on the top of NCDs' priority list in our country and possibly the region.

Diagnosis and management of bone fragility in diabetes: an emerging challenge

Fragility fractures are increasingly recognized as a complication of both type 1 and type 2 diabetes, with fracture risk that increases with disease duration and poor glycemic control. Yet the identification and management of fracture risk in these patients remains challenging. This review explores the clinical characteristics of bone fragility in adults with diabetes and highlights recent studies that have evaluated bone mineral density (BMD), bone microstructure and material properties, biochemical markers, and fracture prediction algorithms (i.e., FRAX) in these patients. It further reviews the impact of diabetes drugs on bone as well as the efficacy of osteoporosis treatments in this population. We finally propose an algorithm for the identification and management of diabetic patients at increased fracture risk.

Worldwide prevalence and incidence of osteoporotic vertebral fractures

We investigated the prevalence and incidence of vertebral fractures worldwide. We used a systematic Medline search current to 2015 and updated as per authors' libraries. A total of 62 articles of fair to good quality and comparable methods for vertebral fracture identification were considered. The prevalence of morphometric vertebral fractures in European women is highest in Scandinavia (26%) and lowest in Eastern Europe (18%). Prevalence rates in North America (NA) for White women ≥50 are 20-24%, with a White/Black ratio of 1.6. Rates in women ≥50 years in Latin America are overall lower than Europe and NA (11-19%). In Asia, rates in women above ≥65 are highest in Japan (24%), lowest in Indonesia (9%), and in the Middle East, Lebanon, rates are 20%. The highest-lowest ratio between countries, within and across continents, varied from 1.4-2.6. Incidence data is less abundant and more heterogeneous. Age-standardized rates in studies combining hospitalized and ambulatory vertebral fractures are highest in South Korea, USA, and Hong Kong and lowest in the UK. Neither a North-South gradient nor a relation to urbanization is evident. Conversely, the incidence of hospitalized vertebral fractures in European patients ≥50 shows a North-South gradient with 3-3.7-fold variability. In the USA, rates in Whites are approximately 4-fold higher than in Blacks. Vertebral fractures variation worldwide is lower than observed with hip fractures, and some of highest rates are unexpectedly from Asia. Better quality representative studies are needed. We investigate the occurrence of vertebral fractures, worldwide, using published data current until the present. Worldwide, the variation in vertebral fractures is lower than observed for hip fractures. Some of the highest rates are from North America and unexpectedly Asia. The highest-lowest ratio between countries, within and across continents, varied from 1.4-2.6. Better quality representative data is needed.

The FRAX-based Lebanese osteoporosis treatment guidelines: rationale for a hybrid model

We describe our approach to develop FRAX-based osteoporosis treatment guidelines in Lebanon, a country with low-moderate fracture rates. A hybrid assessment algorithm that combines a fixed 10 % intervention threshold until age 70 years, and an age-dependent threshold thereafter, was deemed most suitable.

INTRODUCTION

The FRAX risk calculator is used to guide intervention thresholds in several national osteoporosis guidelines. This study aimed to describe the approach in developing FRAX-based osteoporosis treatment guidelines in Lebanon, a country with relatively low fracture rates.

METHODS

We reassessed previous national guidelines combined with an evaluation of age-dependent and fixed FRAX-based intervention threshold models used in the UK, the USA, and Canada. We took into consideration the risk for major osteoporotic fractures (MOF) and the proportions of subjects considered for therapy using such thresholds, before finalizing a model for Lebanon.

RESULTS

The new Lebanese guidelines retained the recommendation to treat individuals with fragility fracture at the hip or spine. A femoral neck T-score ≤-2.5 in subjects without fractures was dropped, since it would imply consideration of therapy for individuals with a 10-year risk for MOF of <10 %, up to age 75 years in women. After considering the impact of both age-dependent and fixed intervention thresholds, we chose a new hybrid algorithm, combining a fixed 10 % treatment threshold until age 70 years and an age-dependent threshold thereafter.

CONCLUSION

The Lebanese FRAX-based hybrid model takes into consideration the risk for MOF and the proportions of subjects considered for treatment. This model avoids consideration of drug therapy in a large proportion of younger subjects at low risk for fracture and targets high risk elderly individuals. It was deemed most suitable for Lebanon and may be an option for other countries with relatively low fracture rates.

Effect of vitamin D replacement on maternal and neonatal outcomes: a randomised controlled trial in pregnant women with hypovitaminosis D. A protocol

INTRODUCTION

The vitamin D recommended doses during pregnancy differ between societies. The WHO guidelines do not recommend routine prenatal supplementation, but they underscore the fact that women with the lowest levels may benefit most. The effects of routine supplementation during pregnancy on maternal and neonatal clinical outcomes have not been investigated in the Middle East, where hypovitaminosis D is prevalent. Our hypothesis is that in Middle Eastern pregnant women, a vitamin D dose of 3000 IU/day is required to reach a desirable maternal 25-hydroxyvitamin D [25(OH)D] level, and to positively impact infant bone mineral content (BMC).

METHODS AND ANALYSIS

This is a multicentre blinded randomised controlled trial. Pregnant women presenting to the Obstetrics and Gynaecology clinics will be approached. Eligible women will be randomised to daily equivalent doses of cholecalciferol, 600 IU or 3000 IU, from 15 to 18 weeks gestation until delivery. Maternal 25(OH)D and chemistries will be assessed at study entry, during the third trimester and at delivery. Neonatal anthropometric variables and 25(OH)D level will be measured at birth, and bone and fat mass assessment by dual-energy X-ray absorptiometry scan at 1 month. A sample size of 280 pregnant women is needed to demonstrate a statistically significant difference in the proportion of women reaching a 25(OH)D level ≥ 50 nmol/L at delivery, and a difference in infant BMC of 6 (10)g, for a 90% power and a 2.5% level of significance. The proportions of women achieving a target 25(OH)D level will be compared between the two arms, using χ(2). An independent t test will be used to compare mean infant BMC between the two arms. The primary analysis is an intention-to-treat analysis of unadjusted results.

ETHICS AND DISSEMINATION

The protocol has been approved by the Institutional Review Board at the American University of Beirut-Lebanon (IM.GEHF.22). The trial results will be published in peer-reviewed medical journals and presented at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT02434380.

Predictors of trabecular bone score in school children

Trabecular bone score (TBS) is a DXA-based tool that assesses bone texture and reflects microarchitecture. It has been shown to independently predict the risk of osteoporotic fracture in the elderly. In this study, we investigated the determinants of TBS in adolescents.

INTRODUCTION

TBS is a gray-level textural measurement derived from lumbar spine DXA images. It appears to be an index of bone microarchitecture that provides skeletal information additional to the standard BMD measurement and clinical risk factors. Our objectives were to characterize the relationship between TBS and both age and pubertal stages and identify other predictors in adolescents.

METHODS

We assessed TBS by reanalyzing spine DXA scan images obtained from 170 boys and 168 girls, age range 10-17 years, gathered at study entry and at 1 year, using TBS software. The results are from post hoc analyses obtained using data gathered from a prospective randomized vitamin D trial. Predictors of TBS were assessed using t test or Pearson's correlation and adjusted using regression analyses, as applicable.

RESULTS

The mean age of the study population was 13.2 ± 2.1 years, similar between boys and girls. Age, height, weight, sun exposure, spine BMC and BMD, body BMC and BMD, and lean and fat mass are all significantly correlated with TBS at baseline (r = 0.20-0.75, p < 0.035). Correlations mostly noted in late-pubertal stages. However, after adjustment for BMC, age remained an independent predictor only in girls.

CONCLUSIONS

In univariate exploratory analyses, age and pubertal stages were determinants of TBS in adolescents. Studies to investigate predictors of TBS and to investigate its value as a prognostic tool of bone fragility in the pediatric population are needed.

Bone and mineral metabolism in patients undergoing Roux-en-Y gastric bypass

Despite effective weight reduction, the impact of bariatric surgery on bone is a major concern. Mechanisms include decreased mechanical loading, calcium and vitamin D malabsorption, deficiency in other nutrients, and alterations in fat- and gut-derived hormones. The evidence to support clinical care pathways to prevent bone loss and fractures is at this point weak.

INTRODUCTION

There is a growing concern regarding the potential deleterious impact of bariatric surgery on bone metabolism. This comprehensive review addresses this controversial topic.

METHODS

We reviewed and analyzed articles evaluating bone metabolism and mechanisms for the ensuing putative bone loss in adult patients exclusively undergoing Roux-en-Y gastric bypass (RYGB) surgery, for the period spanning 1942 till September 2012.

RESULTS

Mechanisms identified to contribute to alterations in bone metabolism after bypass surgery include: decreased mechanical loading, calcium and vitamin D malabsorption with secondary hyperparathyroidism, deficiency in other nutrients, in addition to alterations in adipokines, gonadal steroids, and gut-derived hormones favoring bone loss, with the exception of serotonin and glucagon-like peptide-1. The relative contribution of each of these hormones to changes in bone homeostasis after bypass surgery remains undefined. Bone loss reflected by a decline in bone mineral density (BMD) and an increase in bone turnover markers have been reported in many studies, limited for the most part by the exclusive use of dual energy X-ray absorptiometry. Well-designed long-term prospective trials with fractures as an outcome, and studies investigating the magnitude, reversibility, and impact of the observed metabolic changes on fracture outcomes are lacking.

CONCLUSION

Robust conclusions regarding bone loss and fracture outcome after RYGB surgery cannot be drawn at this time. Although not evidence based, baseline evaluation and sequential monitoring with measurement of BMD and calciotropic hormones seem appropriate, with adequate calcium and vitamin D replacement. Beneficial interventions remain unclear.

PTH level but not 25 (OH) vitamin D level predicts bone loss rates in the elderly

We assessed the impact of calciotropic hormones on bone loss in 195 elderly subjects. After a median follow up of 4 years, parathyroid hormone (PTH) correlated negatively with changes in bone mineral density (BMD) at all skeletal sites. After adjustment for potential predictors of bone loss in the elderly, PTH level alone explained 3% of the variance in BMD changes at the hip.

INTRODUCTION

This study assessed the impact of calciotropic hormones on bone loss rates in an elderly population-based cohort of 195 ambulatory men and women, aged 65-85 years and followed up for a median of 4 years.

METHODS

Calcium intake, serum calcium, and phosphorus were assessed at baseline. Serum creatinine was measured at follow up visit. The 25 (OH) vitamin D [25-OHD] and PTH were measured at baseline and at follow up. Bone mass at the lumbar spine, hip, forearm and total body, as well as body composition was measured at baseline and at follow up by dual energy X-ray absorptiometry.

RESULTS

Mean 25-OHD level was 14.7 ± 6.4 ng/ml and mean PTH level was 47.9 ± 30.4 pg/ml. Age correlated negatively with percent changes in BMD at all skeletal sites (p < 0.05). Changes in body mass index (BMI) and in body composition correlated positively with BMD changes at all sites, except at the forearm. There was no correlation between 25-OHD and changes in BMD except at the trochanter (r = 0.19, p < 0.008). Conversely, PTH negatively correlated with changes in BMD at all skeletal sites (r = -0.14 to -0.27, p < 0.05). This correlation persisted after adjustment for age, changes in BMI, changes in fat mass and lean mass, serum creatinine, calcium intake, and 25-OHD levels. PTH level alone explained 3% of the variance in BMD changes at all hip subregions.

CONCLUSIONS

Serum PTH, but not 25-OHD, predicted bone loss rates in the elderly. Thus, it is important to normalize PTH level when correcting hypovitaminosis D in the elderly.

Osteoporotic fractures, DXA, and fracture risk assessment: meeting future challenges in the Eastern Mediterranean Region

The purpose was to report on the burden of osteoporotic fractures in the Eastern Mediterranean Region (EMR) and the use of bone mineral density (BMD) dual-energy X-ray absorptiometry (DXA) databases for osteoporosis diagnosis. PubMed electronic database was reviewed using the following MeSH terms: "Hip fractures," "Fractures, Compression," "Radius Fractures," "Osteoporosis," "Bone density," and "Middle East" up to July 2009. Incidence of hip fractures varied across the EMR between 100 and 295 per 100,000 person-years in women and 71 and 200 per 100,000 person-years in men. No data were found on other nonvertebral osteoporotic fractures. Prevalence of radiographic vertebral fractures older than 65 yr ranged between 15% and 25% in women and 7.3% and 18% in men. By 2020, the number of hip fractures older than 50 yr would increase by 20%. DXA manufacturer's reference curves for the spine were higher than population-specific ones. At the hip, National Health and Nutrition Examination Survey (NHANES) and population-based curves were comparable. Estimates of the relative risk of vertebral fracture per SD decrease in BMD using NHANES and local data set were similar, that is, 1.61 (1.17-2.23) and 1.49 (1.14-1.95), respectively. The EMR is similar to southern Europe regarding incidence rates of hip fracture, suggesting the health burden to be significant. Using DXA at the hip, population-specific reference databases did not perform better than NHANES on which the FRAX model has been developed highlighting the need for reviewing fracture risk assessment strategies in the EMR.

Interpretation and use of FRAX in clinical practice

The introduction of the WHO FRAX® algorithms has facilitated the assessment of fracture risk on the basis of fracture probability. Its use in fracture risk prediction has strengths, but also limitations of which the clinician should be aware and are the focus of this review

INTRODUCTION

The International Osteoporosis Foundation (IOF) and the International Society for Clinical Densitometry (ISCD) appointed a joint Task Force to develop resource documents in order to make recommendations on how to improve FRAX and better inform clinicians who use FRAX. The Task Force met in November 2010 for 3 days to discuss these topics which form the focus of this review.

METHODS

This study reviews the resource documents and joint position statements of ISCD and IOF.

RESULTS

Details on the clinical risk factors currently used in FRAX are provided, and the reasons for the exclusion of others are provided. Recommendations are made for the development of surrogate models where country-specific FRAX models are not available.

CONCLUSIONS

The wish list of clinicians for the modulation of FRAX is large, but in many instances, these wishes cannot presently be fulfilled; however, an explanation and understanding of the reasons may be helpful in translating the information provided by FRAX into clinical practice.

Hip fracture incidence in Lebanon: a national registry-based study with reference to standardized rates worldwide

Crude incidence rates for hip fractures in individuals aged 50 and above in Lebanon were determined using data from the national hip fracture registry. For the years 2006-2008, crude rates varied between 164 and 188/100,000 for females and between 88 and 106 per 100,000 for males. Using the US 2000 white population as a reference, the calculated age-standardized rates were closest to rates derived for southern Europe.

INTRODUCTION

Owing to the demographic explosion, it is projected that the rates of hip fractures would increase the most in the Middle East and Asia. Few are the population-based studies investigating the incidence of hip fractures in the region.

METHODS

Using the Ministry of Health registry data, this population-based study evaluated the incidence of hip fractures in individuals aged 50 and above in Lebanon for the years 2006, 2007, and 2008.

RESULTS

Hip fracture crude incidence rates varied across the years between 164 and 188 per 100,000 for females and between 88 and 106 per 100,000 for males, with a female/male ratio of 1.6-2.1. The overall mean age (SD) for hip fractures was 75.9 (9.2), 76.8 (9.0), and 77.0 (9.9) years in females in 2006, 2007, and 2008, respectively, and 74.4 (11.6), 76.3 (10.3), and 74.0 (12.1) years in males, respectively. Using the US 2000 white population as a reference, the age-standardized rates were 370.4, 335.1, and 329.0 for females and 109.7, 134.1, and 128.7 for males, for the years 2006, 2007, and 2008, respectively.

CONCLUSIONS

The hip fracture age-standardized incidence rates in the Lebanese subjects receiving Ministry of Health coverage were lower than those found in northern Europe and the US and closest to rates derived for southern Europe.

Global vitamin D status and determinants of hypovitaminosis D

This review describes the vitamin D status in different regions of the world with the objective of understanding the scope of hypovitaminosis D and the factors related to its prevalence that may contribute to the pathogenesis of osteoporosis and fragility fractures.

INTRODUCTION

Vitamin D status has been linked to the pathogenesis of hip fractures as well as other skeletal and non-skeletal disorders. The purpose of this review is to provide a global perspective of vitamin D status across different regions of the world and to identify the common and significant determinants of hypovitaminosis D.

METHODS

Six regions of the world were reviewed-Asia, Europe, Middle East and Africa, Latin America, North America, and Oceania-through a survey of published literature.

RESULTS

The definition of vitamin D insufficiency and deficiency, as well as assay methodology for 25-hydroxyvitamin D or 25(OH)D, vary between studies. However, serum 25(OH)D levels below 75 nmol/L are prevalent in every region studied whilst levels below 25 nmol/L are most common in regions such as South Asia and the Middle East. Older age, female sex, higher latitude, winter season, darker skin pigmentation, less sunlight exposure, dietary habits, and absence of vitamin D fortification are the main factors that are significantly associated with lower 25(OH)D levels.

CONCLUSION

Reports from across the world indicate that hypovitaminosis D is widespread and is re-emerging as a major health problem globally.

Two randomized vitamin D trials in ambulatory patients on anticonvulsants: Impact on bone

OBJECTIVE

To investigate the effects of two doses of vitamin D given over 1 year on bone density in ambulatory patients on long-term antiepileptic drug (AED) therapy.

METHODS

We conducted two parallel, randomized, controlled trials in 72 adults (18 to 54 years old) and 78 children and adolescents (10 to 18 years) on long-term AED therapy. They received either low-dose vitamin D 400 IU/day or high-dose vitamin D 4,000 IU/day (adults) and 2,000 IU/day (children/adolescents). Bone mineral density (BMD) was measured using dual-energy x-ray absorptiometry.

RESULTS

In adults, baseline BMD was lower than that of age- and gender-matched controls vs either a Western or an ethnically identical population. After 1 year, there were significant increases in BMD at all skeletal sites compared to baseline in the high-, but not in the low-dose treatment group. However, BMD at 1 year remained below normal. In children, baseline BMD was normal vs age- and gender-matched controls and showed significant and comparable increases in both treatment groups.

CONCLUSIONS

In ambulatory adults on antiepileptic drugs, high-dose vitamin D therapy substantially increased bone mineral density at several skeletal sites. In children, both doses resulted in comparable increases in bone mass.

Special report on the official positions of the International Society for Clinical Densitometry

The International Society for Clinical Densitometry (ISCD) periodically holds Position Development Conferences (PDCs) for the purpose of establishing standards and guidelines for indications, acquisition, and interpretation of bone density tests. Topics are selected for consideration by the ISCD Scientific Advisory Committee, reviewed by scientific working groups, and presented to an international panel of experts. Topic categories addressed to date include indications for bone density testing, selection of reference databases for T-scores and Z-scores, clinical applications for central and peripheral bone densitometry, serial bone density testing, instrument precision assessment, phantom scanning and calibration testing, requirements for a bone density report, nomenclature, and diagnosis of osteoporosis in postmenopausal women, premenopausal women, men, and children. Following an open session for public comment and discussion, the panel convenes for consideration of each topic and makes recommendations for positions to the ISCD Board of Directors. Recommendations that are accepted become the Official Positions of the ISCD. This Special Report summarizes the methodology of the ISCD PDCs and presents selected Official Positions of general interest.

Predictors of bone mineral density in patients on hemodialysis

Renal osteodystrophy is a universal complication of uremia. Renal failure patients are at risk for low bone mineral density (BMD) and fractures. Parathyroid hormone (PTH) plays a pivotal role in the pathophysiology of uremic bone disease. Histomorphometric studies suggest that the maintenance of PTH levels between two and four times the upper limit of normal is associated with the lowest prevalence of two common forms of osteodystrophy: osteitis fibrosa cystica and adynamic bone disease. The purpose of this study was to investigate whether the above recommendation for PTH levels in dialysis patients corresponds to a more optimal BMD with a special emphasis on diabetic versus nondiabetic subjects. Twenty-eight patients with chronic renal failure on hemodialysis underwent measurement of PTH levels, as well as BMD at the lumbar spine, hip, and forearm. They were divided into three groups based on the mean PTH level over the 5 years prior to having BMD measured. Osteoporosis was diagnosed in 55% of men and 87% of women on dialysis. Predictors of BMD were gender, duration on hemodialysis, and diabetes. Our study supports the histomorphometry-based studies suggesting that the maintenance of intact PTH levels two to four times the upper limit of normal may be associated with better skeletal health in uremic patients on hemodialysis, and that the diabetic subgroup is at particular risk for low BMD.

Low peak bone mineral density in healthy Lebanese subjects

Osteoporosis is a major public health problem in Western countries and is projected to have a similar impact in the Middle East. It has been suggested that peak bone mineral density (BMD), a major determinant of osteoporotic fractures later in life, may be lower in this part of the world compared with the Western world. However, subjects have not been randomly selected or systematically screened to rule out secondary causes of bone loss. The purpose of this study was to determine peak bone mass and lifestyle risk factors for bone loss in a randomly chosen sample of healthy Lebanese subjects from the greater Beirut area. Subjects 25-35 years of age were randomly selected from greater Beirut, which comprises one third of the Lebanese at large, and studied during the Fall of 1999. BMD was measured at the lumbar spine, hip, forearm, and total body. A questionnaire on lifestyle factors was administered to all subjects. Results were compared with the database of subjects from the USA provided by the manufacturer, and to the NHANES database for the total hip. Two hundred thirteen subjects were studied; 45 subjects rotated at all three centers for cross-calibration purposes. Peak BMD in Lebanese subjects was 0.2-0.9 SD below that of peak BMD in American subjects, depending on skeletal site, gender, and densitometer. These differences persisted after attempting to adjust for body size. Osteoporosis and osteopenia were more prevalent than in healthy young Americans. Height, weight, and total body fat were the most significant correlates of BMD/bone mineral content (BMC), accounting for 0.3-0.7 of the variance in bone mass measurement. Lifestyle factors had a very modest but significant contribution to bone mass variance. This is the first population-based study from the Middle East demonstrating that peak BMD is slightly lower in Lebanese subjects compared as with an established database from the USA. Due to the selection of relatively healthier subjects in our study than in the NHANES study, the actual differences between the two populations may be even greater. The impact of our findings on the epidemiology of osteoporotic fractures in Lebanon remains to be determined.

Effect of antiepileptic drugs on bone density in ambulatory patients

BACKGROUND

Long-term antiepileptic drug (AED) use causes multiple abnormalities in calcium and bone metabolism that have been most extensively described in institutionalized patients. The objective is to determine the effect of AED on vitamin D levels and bone density in ambulatory patients and to compare the effects of enzyme-inducing and -noninducing AED and of single vs multiple therapy on bone density.

METHODS

A cross-sectional evaluation was conducted of 71 patients (42 adults and 29 children/adolescents) on anticonvulsant therapy for at least 6 months who presented to neurologists at a tertiary referral center. Bone mineral density (BMD) as well as serum 25 hydroxy-vitamin D (25-OHD) levels were measured. A detailed questionnaire assessing calcium intake as well as previous and current intake of antiepileptic medications was administered to all patients.

RESULTS

Over 50% of adults and children/adolescents had low 25-OHD levels, but this finding did not correlate with BMD. Antiepileptic therapy decreased BMD in adults. Generalized seizures, duration of epilepsy, and polypharmacy were significant determinants of BMD, more so at skeletal sites enriched in cortical bone. Subjects on enzyme-inducing drugs such as phenytoin, phenobarbital, carbamazepine, and primidone tended to have lower BMD than those on noninducers such as valproic acid, lamotrigine, clonazepam, gabapentin, topamirate, and ethosuximide.

CONCLUSION

Epilepsy and its therapy, including the newer drugs, are risk factors for low bone density, irrespective of vitamin D levels. Skeletal monitoring with the institution of appropriate therapy is indicated in patients on chronic antiepileptic therapy.

Hypercalcemia in Langerhans' cell granulomatosis with elevated 1,25 dihydroxyvitamin D (calcitriol) level

A 48-year-old woman presented with a history of premature menopause, polyuria, polydipsia, fever, and diffuse bony tenderness. Her evaluation revealed central diabetes insipidus, hypothalamic amenorrhea, an elevated free calcium on multiple occasions with an elevated 1,25 dihydroxyvitamin D level, and osteoporosis by densitometry. Skeletal series revealed multiple lytic lesions involving the long bones. The diagnosis of Langerhans' cell granulomatosis was made. She was treated with hormone replacement therapy, radiotherapy, and vinblastine, with a dramatic improvement in her pain and a near normalization of her free calcium. Whereas hypercalcemia has been described in several granulomatous disorders and is secondary to unregulated extrarenal production of 1,25 dihydroxyvitamin D, it is, however, extremely rare in Langerhans' cell granulomatosis. This is the first case report of Langerhans' cell granulomatosis with hypercalcemia and documented elevated increased 1,25 dihydroxyvitamin D level that responded to the treatment of her primary disease.

The effects of age and gender on parathyroid hormone dynamics

BACKGROUND AND AIMS

Hyperparathyroidism is a risk factor for bone loss. An age-related increase in parathyroid hormone (PTH) level has been demonstrated in several studies. It has been suggested that the type II osteoporotic syndrome, a condition of increased prevalence among elderly women, may be at least partially caused by elevations in intact parathyroid hormone (iPTH) levels. To date, however, the effects of age and gender per se on PTH dynamics in healthy subjects independent of other risk factors such as vitamin D deficiency and/or impaired renal function that can impact on parathyroid function, remain unknown. In this study, we used citrate and calcium (Ca) infusions to characterize the impact of age and gender on PTH dynamics in normal subjects.

SUBJECTS AND METHODS

Twelve young women with mean age +/- SD of 26.4 +/- 1.6 years, 12 young men with mean age of 26.6 +/- 1.3 years, 12 older women with mean age of 68.6 +/- 1.3 years and 12 older men with mean age of 67.2 +/- 1.6 years were studied. The sigmoidal curves relating serum iPTH to serum levels of ionized Ca (Cai) were characterized by maximal and minimal iPTH levels, the set-points (levels of Cai causing half-maximal suppression of iPTH), and the slopes of the curves at the set-points.

RESULTS

Baseline serum Ca, Cai, 25 hydroxyvitamin D [25(OH)D] and 1,25 dihydroxyvitamin D [1,25(OH)2D3] levels, as well as the set-points, slopes and minimal values of the sigmoidal curves relating Cai to iPTH, did not differ among the four groups. iPTH levels at baseline were slightly but not significantly higher in the older age groups (P = 0.18). The maximal iPTH level was 25% higher in the older women than in the younger women, although this difference was not significant (P = 0.29). However, the integrated iPTH responses calculated from the areas under the curves (AUC) of iPTH levels vs. time during the calcium and citrate infusions were significantly higher in postmenopausal women than in young women during both infusions and in older men than in young men during the calcium infusion. There was no effect of gender on serum iPTH levels.

CONCLUSIONS

In both women and men, ageing per se, independent of changes in vitamin D economy or renal function, is associated with an increase in integrated PTH secretory response to changes in serum calcium. No alterations in the Cai/iPTH set-point were present. The biological relevance of these modest increments in integrated iPTH levels during dynamic testing in older healthy men and women remain uncertain.

Calcium modulation of the renin-aldosterone axis

Changes in the extracellular calcium concentration have important effects on hormone secretion. In vitro, kidney juxtaglomerular cells have been shown to secrete renin in an inverse relationship to the extracellular calcium concentration. The effect of physiologic changes in calcium on renin secretion in humans is less clear. We therefore investigated the effects of physiologic changes in extracellular calcium levels on renin and aldosterone secretion in 7 healthy men. Serum ionized calcium, ACTH, plasma renin activity (PRA), and aldosterone levels were serially measured during 90-min infusions of dextrose, disodium edetate (EDTA) and calcium gluconate, and the latter two infusions were repeated with dexamethasone pre-treatment. ACTH levels decreased during the 5% dextrose in water and the EDTA infusions but increased during the calcium infusion. Similarly, PRA and aldosterone levels fell during the D5W and EDTA infusions but this decrease was absent with increments in calcium levels. Dexamethasone administration suppressed ACTH and the aldosterone response to calcium but did not affect the PRA response to the calcium infusion. Our data indicate that increases in calcium within the physiological range blunt the diurnal decline in both PRA and aldosterone. This appears to be a direct effect of calcium on PRA but mediated through ACTH in the case of aldosterone.