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Biomedical subjects

L K Bachrach

Publications and source records attributed to L K Bachrach.

At least 19 recordsLinked to original sources
PubMed2001

Assessment of bone mineralization following renal transplantation in children: limitations of DXA and the confounding effects of delayed growth and development.

Pediatric renal transplantation recipients have numerous risk factors for decreased bone mass, including the underlying renal disease, nutritional deficits, decreased physical activity, inflammation and exposure to steroid therapy. The assessment of bone mineralization in children following renal transplantation is fraught with difficulty. Dual energy x-ray absorptiometry (DXA) is the most commonly employed tool to assess bone mineralization. However, DXA has important limitations in children and in individuals with renal disease. This brief review will examine the expected gains in bone size and bone mass during growth and the mechanisms by which renal failure and steroid therapy interrupt these process. In addition, the limitations of DXA for detecting impaired bone mineralization in children with renal disease are reviewed and alternative approaches explored.

Absorptiometry, Photon↗
PubMed2001

Calcaneus ultrasound measurements in a convenience sample of healthy youth.

We examined age-related changes in quantitative ultrasound of the calcaneus in 311 healthy males and females ages 6.6-20 yr using the Lunar Achilles ultrasound device. This equipment has been adapted for pediatric use with the provision of shims designed to properly position smaller feet relative to the transducers. Broadband ultrasound attenuation (BUA) (decibels/megahertz), speed of sound (SOS) (meters/second), and stiffness index (SI) (percent) increased across the age range until a plateau was reached at 16-18 yr. BUA increased by 40%, SOS by 4%, and SI by 80% across this age range. There was no gender difference in age-related gains. Age, weight, height, and hours of weight-bearing physical activity were all significantly associated with BUA, SOS, and SI. After controlling for age and weight, hours of weight-bearing physical activity showed little to no additional effect on these parameters. Short-term in vivo precision using this device was similar in children to that observed in adults in our laboratory; coefficients of variation for between-day measurements were 1.8, 0.6, and 3.2% for BUA, SOS, and SI, respectively. These data support the feasibility of using the Lunar Achilles in evaluating pediatric bone mass. The ability of this technique to discriminate between osteopenic and normal children remains to be determined.

Adolescent↗
PubMed2000

Use of hormone replacement therapy to reduce the risk of osteopenia in adolescent girls with anorexia nervosa.

PURPOSE: To assess how commonly hormone replacement therapy (HRT) and other measures are prescribed for the treatment of osteopenia in children and adolescents with anorexia nervosa (AN). METHODS: A self-administered questionnaire was distributed and completed by allopathic and osteopathic physician members of the Society for Adolescent Medicine at its 1998 annual meeting. The questionnaire was also mailed and E-mailed between March 1998 and February 1999. Descriptive statistics included percentages and measures of central tendency. RESULTS: The questionnaire was completed by 394 of the 1029 physicians surveyed (38.3%). Of the 268 respondents who treated patients with AN under the age of 18 years, 77.6% prescribed HRT. The decision to prescribe HRT was influenced by patient's age but not by bone mineral status. Among those who prescribed HRT, additional therapies included increased caloric intake (89.4%), weight gain (82.2%), increased calcium intake (84.1%), a change in exercise patterns (59.1%), and vitamin D supplementation (37.0%). Only 59 (22.0%) did not use HRT as a treatment modality. One-third of nonprescribers cited the lack of evidence of efficacy of HRT in preventing osteopenia. More recent medical graduates were less likely to prescribe HRT. CONCLUSIONS: This survey suggests that practitioners caring for adolescent females with AN commonly prescribe HRT for the treatment of osteopenia despite the paucity of evidence demonstrating that it effectively prevents or reverses bone loss associated with this disorder.

Adolescent↗
PubMed2000

Dual energy X-ray absorptiometry (DEXA) measurements of bone density and body composition: promise and pitfalls.

Dual energy X-ray absorptiometry (DEXA) is widely viewed as the preferred method to assess pediatric bone mineral content because of its speed, precision, and minimal radiation exposure, and the availability of pediatric reference data. DEXA can also be used to estimate body composition precisely with minimal patient cooperation. Accurate interpretation of DEXA data in children requires consideration of bone size, pubertal stage, skeletal maturation, ethnicity and body composition. Bone mineral content may be underestimated in smaller children and overestimated in larger ones. Corrections for skeletal age or sexual maturity may also be needed in children with advanced or delayed growth. Errors in body composition measurement occur because body fat and fat-free mass are not distributed uniformly. In addition, fat mass present adjacent to bone will influence the measurement of bone mineral content. In conclusion, DEXA is a valuable tool for assessing pediatric bone health, but accurate interpretation of densitometry results requires recognition of a myriad of pitfalls.

Absorptiometry, Photon↗
PubMed1999

Influence of pre-adolescent diet on quantitative ultrasound measurements of the calcaneus in young adult women.

Nongenetic determinants of quantitative ultrasound (QUS) properties of the bone remain to be identified. The purpose of this study was to determine relationships between early adolescent diet and QUS bone measurements taken in young adulthood. Subjects were participants in the 10-year longitudinal National Heart, Lung, and Blood Institute Growth and Health Study (NGHS). QUS parameters measured at the calcaneus in a convenience subsample of 63 18- to 19-year-old black and white women were correlated with dietary data collected when the subjects were aged 9-11 years. We hypothesized that pre-adolescent intake of calcium, magnesium, vitamin C and protein, nutrients known to be associated with bone development, would be associated with QUS measurements in young women. Stepwise multiple regression analysis, controlling for race, height and weight, demonstrated that pre-adolescent intake of calcium and magnesium were positively related to QUS parameters (calcium with broadband ultrasound attenuation, and magnesium with speed of sound and bone velocity). Our findings suggest that pre-adolescent diet may be associated with bone properties as measured by ultrasound. Further investigations of this relationship may yield a deeper understanding of the impact of diet on skeletal development. The small size of the convenience sample used for the analysis precludes stronger inferences at this time.

Adolescent↗
PubMed1999

A comparison of calcaneus ultrasound and dual X-ray absorptiometry in healthy North American youths and young adults.

Quantitative ultrasound is the newest noninvasive method to be accepted for assessing bone mineral in adults. Heel ultrasound measurements correlate with bone density measurements by dual X-ray absorptiometry (DXA) and predict fracture risk in adults. Far less is known about the value of calcaneus ultrasound (CUS) in children. We determine spine, femoral neck, and whole-body bone mineral by DXA and heel bone mass by CUS in 125 youths (69 females, 56 males) ages 9-25 yr. CUS and DXA measurements of bone mass increased with age and pubertal development during adolescence in a parallel fashion. Among females, Tanner stage was a stronger predictor than age for all CUS and DXA measurements, and among males, pubertal stage was a stronger predictor for spine bone mineral apparent density (BMAD) and femoral bone mineral density (BMD). CUS measurements correlated moderately well with DXA measurements of the spine, femoral neck, and whole-body BMD and spine BMAD (r = 0.23-0.58, p < 0. 008). CUS warrants further study as a tool for assessing bone mineral acquisition in children.

Absorptiometry, Photon↗
PubMed1999

Natural history of growth hormone receptor deficiency.

This review discusses the natural history of growth hormone receptor deficiency (GHRD) in relation to epidemiology, mortality, growth, certain aspects of body composition, and intellectual development. The majority of affected individuals are of Semitic origin and 90% come from the Indian peninsula, the Middle East, or elsewhere in the Mediterranean. There is a twofold increased mortality before the age of 7 years for children with GHRD. Affected adults may have increased cardiovascular risk resulting from increased total cholesterol and low-density lipoprotein cholesterol, unrelated to adiposity or insulin resistance. Intrauterine growth is affected minimally, if at all. Within a genetically homogeneous population in Ecuador, postnatal growth effects are as variable as in a large genetically heterogeneous population. There is no influence of parental heights. Areal bone mineral density is reduced in adults with GHRD, but estimated volumetric bone density (bone mineral apparent density) is normal. Intellectual development is unaffected by GHRD.

Adult↗
PubMed1999

Bone mineral acquisition in healthy Asian, Hispanic, black, and Caucasian youth: a longitudinal study.

Ethnic and gender differences in bone mineral acquisition were examined in a longitudinal study of 423 healthy Asian, black, Hispanic, and white males and females (aged 9-25 yr). Bone mass of the spine, femoral neck, total hip, and whole body was measured annually for up to 4 yr by dual energy x-ray absorptiometry. Age-adjusted mean bone mineral curves for areal (BMD) and volumetric (BMAD) bone mineral density were compared for the 4 ethnic groups. Consistent differences in areal and volumetric bone density were observed only between black and nonblack subjects. Among females, blacks had greater mean levels of BMD and BMAD at all skeletal sites. Differences among Asians, Hispanics, and white females were significant for femoral neck BMD, whole body BMD, and whole body bone mineral content/height ratio, for which Asians had significantly lower values; femoral neck BMAD in Asian and white females was lower than that in Hispanics. Like the females, black males had consistently greater mean values than nonblacks for all BMD and BMAD measurements. A few differences were also observed among nonblack male subjects. Whites had greater mean total hip BMD, whole body BMD, and whole body bone mineral content/height ratio than Asian and Hispanic males; Hispanics had lower spine BMD than white and Asian males. The tempo of gains in BMD varied by gender and skeletal site. In females, total hip, spine, and whole body BMD reached a plateau at 14.1, 15.7, and 16.4 yr, respectively. For males, gains in BMD leveled off at 15.7 yr for total hip and at age 17.6 yr for spine and whole body. Black and Asian females and Asian males tended to reach a plateau in BMD earlier than the other ethnic groups. The use of gender- and ethnic-specific standards is recommended when interpreting pediatric bone densitometry data.

Absorptiometry, Photon↗
PubMed1998

Bone acquisition and loss in children and adults with cystic fibrosis: a longitudinal study.

OBJECTIVES: To determine patterns of bone mineral acquisition in children and young adults with cystic fibrosis (CF) and to identify clinical and laboratory correlates of change in bone mineral density (BMD). STUDY DESIGN: Bone mineral and clinical status were assessed in 41 patients with CF (26 female, aged 9 to 50 years) at baseline and 1.5 years later. Bone mineral content of the lumber spine, femoral neck, and whole body was determined by dual-energy x-ray absorptiometry and expressed as BMD and bone mineral apparent density (BMAD). Changes in weight, height, pubertal status, glucocorticoid use, physical activity, disease severity, and biochemical markers of bone turnover were examined for associations with changes BMD and BMAD. RESULTS: Mean BMD Z-scores (adjusted for age and sex) were reduced at the spine, hip, and whole body at baseline in both adults and youths, and decreased further at all sites among youths at follow-up (-0.4 at spine, p < 0.05; -0.3 at hip, p < 0.10; -0.5 for whole body, p < 0.0005). These data indicate failure to gain bone mineral at the expected rate. BMAD was also reduced at follow-up, suggesting that the observed osteopenia could not be explained by small bone size. Bone loss at multiple sites was observed in four youths and two adults. In general glucocorticoid use, change in body mass, physical activity, and disease severity were the most significant correlates for change in BMD and in BMD Z-score. CONCLUSIONS: Osteopenia in CF generally reflects inadequate gains in bone mineral, although bone loss may occur, particularly in patients requiring glucoc therapy. Late gains in bone mineral may accompany weight gain and pubertal development, but the catch-up appears to be incomplete.

Adolescent↗
PubMed1998

Bone mineral, histomorphometry, and body composition in adults with growth hormone receptor deficiency.

Growth hormone (GH) and insulin-like growth factor I (IGF-I) deficiencies have been associated with osteopenia in both children and adults. To examine the effects of growth hormone resistance on bone mineral and body composition, we studied 11 adults (mean age 30 years) with growth hormone receptor deficiency (GHRD, Laron syndrome) and 11 age- and gender-matched controls from Southern Ecuador. Bone mineral and body composition were determined by dual-energy X-ray absorptiometry. Bone physiology was assessed with biochemical markers of bone turnover and dynamic bone histomorphometry. Bone size and body composition differed markedly between subjects with GHRD and controls. Affected adults were 40 cm shorter than controls, had significantly less lean body mass, and had increased percent body fat. Bone mineral content and density (BMD) at the spine, femoral neck, and whole body were significantly lower in adults with GHRD than in controls. Mean BMD Z scores were -1.5 to -1.6 at all sites in affected women and -2.2 to -2.3 in men with GHRD. Estimated volumetric bone density (BMAD) at the spine and femoral neck, however, was not reduced in GHRD. Spine BMAD was 0.210 +/- 0.025 versus 0.177 +/- 0.021 for affected women versus controls (p < 0.05) and 0.173 +/- 0.018 versus 0.191 +/- 0.025 for men with GHRD versus normals (p = 0.31). Urinary pyridinoline concentrations were significantly greater in adults with GHRD than in controls, while type I collagen C-telopeptide breakdown products and markers of bone formation did not differ. Differences in histomorphometry were limited to a reduction in trabecular connectivity; bone volume and formation rate were similar to controls. These data confirm the importance of the GH/IGF axis in regulating bone size and body composition. The contribution of these peptides to the acquisition and maintenance of bone mineral is less certain since volumetric bone density was preserved despite low levels of IGF-I and IGFBP-3 associated with GH resistance.

Absorptiometry, Photon↗
PubMed1997

Correspondence between theoretical models and dual energy x-ray absorptiometry measurements of femoral cross-sectional growth during adolescence.

We have developed an analytical model of long bone cross-sectional ontogeny in which appositional growth of the diaphysis is primarily driven by mechanical stimuli associated with increasing body mass during growth and development. In this study, our goal was to compare theoretical predictions of femoral diaphyseal structure from this model with measurements of femoral bone mineral and geometry by dual energy x-ray absorptiometry. Measurements of mid-diaphyseal femoral geometry and structure were made previously in 101 Caucasian adolescents and young adults 9-26 years of age. The data on measured bone mineral content and calculated section modulus were compared with the results of our analytical model of cross-sectional development of the human femur over the same age range. Both bone mineral content and section modulus showed good correspondence with experimental measurements when the relationships with age and body mass were examined. Strong linear relationships were evident for both parameters when examined as a function of body mass.

Absorptiometry, Photon↗