Femoral Neck Body Bone Mineral Density Research Articles

ANDROGEN RECEPTOR CAG AND GGN REPEAT POLYMORPHISMS AND BONE MASS IN BOYS AND GIRLS.

the human androgen receptor (AR) gene possesses two trinucleotide polymorphic repeats, (CAG and GGN) that affect the amount of AR protein translated. In this study, we genotyped these polymorphic tracts in a representative sample of Caucasian children (Tanner ≤ 5), 152 boys (11.5 } 2.6 yrs) and 116 girls (10.1 } 3.2 yrs) from Spain and investigated their association with bone mass. the length of CAG and GGN repeats was determined by PCR and fragment analysis. Body composition was assessed by dual energy x-ray absorptiometry (DXA). Individuals were grouped as CAG short (CAGS) if harboring repeat lengths of ≤ 21 and CAG long (CAGL) if CAG > 21. Moreover, subjects were grouped as GGN short (GGNS) if harboring repeat lengths of ≤ 23 and GGN long (GGNL) if GGN > 23. in boys, significant differences in height, body mass, whole body bone mineral density (BMD) and content (BMC), upper extremities BMC, lower extremities BMC, femoral neck BMD, Ward's triangle BMC and BMD and lumbar spine BMD were observed between CAGS and CAGL groups (P < 0.05). Thus, upper extremities BMD differed between GGNS and GGNL groups. After adjusting for confounding variables, only upper extremities BMD between GGNS and GGNL groups remained significant (P < 0.05). No differences were observed in girls in any measured site in relation to either CAG or GGN polymorphisms length. our results support the hypothesis that longer alleles of the AR CAG and GGN polymorphisms are associated with increased bone mass in prepubertal boys.

An altered hormonal profile and elevated rate of bone loss are associated with low bone mass in professional horse-racing jockeys

Horse-racing jockeys are a group of weight-restricted athletes, who have been suggested as undertaking rapid and extreme weight cycling practices in order to comply with stipulated body-mass standards. The aim of this study was to examine bone mass, turnover and endocrine function in jockeys and to compare this group with age, gender and body mass index matched controls. Twenty male professional jockeys and 20 healthy male controls participated. Dual energy X-ray absorptiometry scans and early morning fasting blood and urine samples were used to measure bone mass, turnover and a hormonal profile. Total body bone mineral density (BMD) was significantly lower in jockeys (1.143±0.05 vs. 1.27±0.06gcm(-3), p<0.01). Bone resorptive activity was elevated in the jockey group as indicated by significantly higher urinary NTx/creatinine (76.94±29.52 vs. 55.9±13.9nmolmmol(-1), p<0.01), resulting in a significantly negative uncoupling index between bone resorption and formation. Sex hormone binding globulin (SHBG) levels were significantly higher in jockeys (41.21±9.77 vs. 28.24±9.98nmolL(-1), p<0.01) with a lower percentage of bioavailable testosterone (48.89±7.38 vs. 59.18±6.74%, p<0.01). SHBG and insulin-like growth factor-1 were independent predictors of total body and femoral neck BMD, respectively (p<0.05). In conclusion, it appears that professional jockeys have an elevated rate of bone loss and reduced bone mass that appears to be associated with disrupted hormonal activity. It is likely that this may have occurred in response to the chronic weight cycling habitually experienced by this group.

Weight regulation and bone mass: a comparison between professional jockeys, elite amateur boxers, and age, gender and BMI matched controls

The aim of this study was to compare bone mass between two groups of jockeys (flat: n=14; national hunt: n=16); boxers (n=14) and age, gender and BMI matched controls (n=14). All subjects underwent dual energy X-ray absorptiometry (DXA) scanning for assessment of bone mass, with measurements made of the total body, vertebra L2-4 and femoral neck. Body composition and the relative contribution of fat and lean mass were extrapolated from the results. Data were analysed in accordance with differences in body composition, in particular, height, lean mass, fat mass and age. Both jockey groups were shown to display lower bone mass than either the boxers or control group at a number of sites including total body bone mineral density (BMD) (1.019±0.06 and 1.17±1.05 vs. 1.26±0.01 and 1.26±0.06gcm(-2) for flat, national hunt, boxer and control, respectively), total body bone mineral content (BMC) less head, L2-4 BMD and femoral neck BMD and BMC (p<0.05). Regression analysis revealed that lean mass and height were the primary predictors of total body BMC, although additional group-specific influences were present which reduced bone mass in the flat jockey group and enhanced it in the boxers (R (2)=0.814). Reduced bone mass in jockeys may be a consequence of reduced energy availability in response to chronic weight restriction and could have particular implications for these athletes in light of the high risk nature of the sport. In contrast, the high intensity, high impact training associated with boxing may have conveyed an osteogenic stimulus on these athletes.

Predictors of bone mineral density in aging healthy men varies by skeletal site.

Factors contributing to the pathogenesis of osteoporosis in women are well defined. However, changes in bone mineral metabolism in aging men and the role of various factors in the pathogenesis of age-related bone loss in men are less well understood. To further clarify these changes, serum and urine biochemical parameters, and lumbar spine, hip, and total body bone mineral density (BMD) were evaluated in a small sample of 45 healthy men aged 20-80 years, and multiple regression models were developed to predict age-related bone loss. Serum calcium, phosphate, albumin, creatinine clearance, osteocalcin, C-terminal propeptide of type I procollagen, log-free androgen index, dehydroepiandrosterone sulfate (DHEA-S), and androstenedione decreased with age, and serum sex hormone binding globulin and urine total and free pyridinoline increased with age. Femoral neck BMD decreased with age, but remained stable at the other sites measured. Multiple regression analysis indicated that serum phosphate, DHEA-S, and intact parathyroid hormone (PTH) predicted lumbar spine BMD. Age, serum phosphate, and PTH predicted femoral neck BMD. Urine-free deoxypyridinoline alone predicted femoral greater trochanter BMD. Weight, serum creatinine, and urine-free deoxypyridinoline predicted total body BMD. We conclude that predictor variables of bone density vary by skeletal site in healthy men. Alterations in adrenal androgens, phosphate, and PTH may be important in the pathogenesis of bone loss with aging in men.

Body composition in systemic lupus erythematosus.

The objectives were to determine the body composition, and the effects of disease and corticosteroid therapy on body composition, in a population of female patients with systemic lupus erythematosus (SLE). All female SLE patients managed through a single centre were invited to participate in a cross-sectional study of body composition. Data were collected by standardized interview and examination, and review of medical records. Body composition was assessed by dual-energy X-ray absorptiometry (DXA). Eighty-two subjects were evaluated, 30 of whom were post-menopausal. Univariate linear regression analysis revealed a significant association of reduced fat-free mass with SLE severity [as measured by the Systemic Lupus International Collaborative Clinics (SLICC)] (P = 0.020), a history of corticosteroid exposure (P = 0.043) and age (P = 0.048). Reduced total body bone mineral density (BMD) was also significantly associated with SLICC (P < 0.001) and corticosteroid exposure (P = 0.017), and with age (P < 0.001), post-menopausal status (P = 0.003) and the duration of menopause (P < 0.001). Stepwise multiple linear regression analysis revealed a significant association between fat-free mass and total body, lumbar spine and femoral neck BMD (P = 0.007, P = 0.025, P = 0.003, respectively). Fat mass was significantly associated only with lumbar spine BMD (P = 0.008). In this SLE population, disease severity and corticosteroid exposure were independently associated with a negative effect both on total body BMD and on fat-free mass. Fat-free mass was a significant predictor of lumbar spine, femoral neck and total body BMD.

Hip bone mineral density is improved by high-impact aerobic exercise in postmenopausal women and men over 50 years.

Fifteen men and women (six men) between the ages of 50 and 73 years were recruited to begin keep-fit classes. They were matched for sex, age, menopausal status and mass to 15 non-exercising controls. The keep-fit classes were two to three times a week and included high-impact exercise, including step and jumping exercises specifically to load the proximal femur and spine. Proximal femur, lumbar spine and total body bone mineral density (BMD) were measured at 0 and 12 months. Urinary pyridinoline (Pyr) and deoxypyridinoline (dPyr) crosslinks were measured every 6 months to assess bone resorption. Quadriceps isometric strength was measured every 6 months. BMD increased non-significantly at the femoral neck [1.57 (0.8)%] and Wards triangle [1.97 (1.4)%], and significantly at the greater trochanter 2.21 (0.9)% (P = 0.02) in the exercise group. Femoral neck BMD decreased by -1.9(0.8)% (P = 0.049) in the control group, which was significantly different from the change in the exercise group (P = 0.009). BMD did not change at the Wards triangle or trochanter in the controls. Lumbar spine BMD did not change in either group. Total body BMD did not change in the exercise group, but decreased by -0.79 (0.3)% (P = 0.02) in the controls. Following 6 months of the exercise classes. Pyr and dPyr crosslinks were significantly reduced [-19.0 (7.2)%; P = 0.0019 and -20.0 (7.7)%; P = 0.021 respectively]. There was no significant change in crosslinks after 1 year, and no change at any time in the controls. Quadriceps strength changed by 5.4 (3.7)% in the exercise group and by -6.9 (2.5)% (P = 0.01) in the control group after 12 months, being significant between groups (P = 0.008). This study suggests that high-impact, aerobic exercise in postmenopausal women and men over 50 years old is feasible and effective at maintaining muscle strength and increasing proximal femur BMD but not spine or total body BMD.