Effect of subclinical hypothyroidism on body fluid compartments.

OBJECTIVE: The present study was aimed to assess the effects of subclinical hypothyroidism on body composition (BC). SUBJECTS: Thirty-one women (age: 37 +/- 9.9 years) with a wide range of body mass index (BMI) were studied. Subclinical hypothyroidism was defined by a basal TSH > or = 4 mU/L and/or TRH stimulated peak > or = 30 mU/L. MEASUREMENTS: For each subject, weight, height, BMI, multifrequency bioelectrical impedance spectroscopy (BIS) and D2O and NaBr dilution tests were performed to assessed total body water (TBW) and extracellular water (ECW). Thyroid function (basal and TRH stimulated TSH, free T3, and free T4) were determined from fasting blood samples for all subjects. Total body dual energy X-ray absorptiometry (DXA) were used to measure fat mass (FM) and lean mass (Lean). RESULTS: The results of BIS were compared with the TBW and ECW estimated by the dilution techniques on the same individuals. The correlation was R2 = 0.65 for impedance at 5 kHz and ECW by NaBr and R2 = 0.72 for impedance at 100 kHz and TBW by D2O. Intracellular water (ICW) was calculated as differences between TBW and ECW measured by dilution methods. Percent of ECW and ICW were related to BMI (ANOVA, p < 0.001). No difference in TBW, body water distribution and body composition related to thyroid function was demonstrated. CONCLUSIONS: In our patients affected with subclinical hypothyroidism, with or without obesity, only obesity appeared related to TBW, ECW and ICW; the subclinical hypothyroidism, on the contrary, had no effect on compartments of body fluids. Bioimpedance is a valid tool to assess body fluid distribution in subclinical hypothyroidism.     

Effect of bone mineral content on the tensile properties of cortical bone: experiments and theory

The effect of mineral volume fraction on the tensile mechanical properties of cortical bone tissue is investigated by theoretical and experimental means. The mineral content of plexiform, bovine bone was lowered by 18% and 29% by immersion in fluoride solutions for 3 days and 12 days, respectively. The elastic modulus, yield strength and ultimate strength of bone tissue decreased, while the ultimate strain increased with a decrease in mineral content. The mechanical behavior of bone tissue was modeled by using a micromechanical shear lag theory consisting of overlapped mineral platelets reinforcing the organic matrix. The decrease in yield stress, by the 0.002 offset method, of the fluoride treated bones were matched in the theoretical curves by lowering the shear yield stress of the organic matrix. The failure criterion used was based on failure stresses determined from a failure envelope (Mohr's circle), which was constructed using experimental data. It was found that the model predictions of elastic modulus got worse with a decrease in mineral content (being 7.9%, 17.2% and 33.0% higher for the control, 3-day and 12-day fluoride-treated bones). As a result, the developed theory could not fully predict the yield strain of bones with lowered mineral content, being 12.9% and 21.7% lower than the experimental values. The predicted ultimate stresses of the bone tissues with lower mineral contents were within +/- 10% of the experimental values while the ultimate strains were 12.7% and 26.3% lower than the experimental values. Although the model developed in this study did not take into account the presence of hierarchical structures, voids, orientation of collagen molecules and micro cracks, it still indicated that the mechanical properties of the organic matrix depend on bone mineral content.     

Relation of bone mineral density and content to mineral content and density of the fat-free mass.

Differences in the mineral fraction of the fat-free mass (M(FFM)) and in the density of the FFM (D(FFM)) are often inferred from measures of bone mineral content (BMC) or bone mineral density (BMD). We studied the relation of BMC and BMD to the M(FFM) and D(FFM) in a heterogeneous sample of 216 young men (n = 115) and women (n = 101), which included whites (n = 155) and blacks (n = 61) and collegiate athletes ( n = 132) and nonathletes (n = 84). Whole body BMC and BMD were determined by dual-energy X-ray absorptiometry (DXA; Hologic QDR-1000W, enhanced whole body analysis software, version 5.71). FFM was estimated using a four-component model from measures of body density by hydrostatic weighing, body water by deuterium dilution, and bone mineral by DXA. There was no significant relation of BMD to M(FFM) (r = 0.01) or D(FFM) (r = -0.06) or of BMC to M(FFM) (r = -0.11) and a significant, weak negative relation of BMC to D(FFM) (r = -0.14, P = 0.04) in all subjects. Significant low to moderate relationships of BMD or BMC to M(FFM) or D(FFM) were found within some gender-race-athletic status subgroups or when the effects of gender, race, and athletic status were held constant using multiple regression, but BMD and BMC explained only 10-17% of the variance in M(FFM) and 0-2% of the variance in D(FFM) in addition to that explained by the demographic variables. We conclude that there is not a significant positive relation of BMD and BMC to M(FFM) or D(FFM) in young adults and that BMC and BMD should not be used to infer differences in M(FFM) or D(FFM).     

Suit therapy versus whole-body vibration on bone mineral density in children with spastic diplegia

Objectives:Osteoporosis because of physical inactivity is one of the major complications associated with neuromuscular disorders. The study aimed to compare using Suit therapy and whole-body vibration in addition to selected physical therapy program to improve Bone Mineral Density in children with cerebral palsy of spastic diplegia.Methods:Forty-six patients were classified randomly into two equal groups. Patients in the group (A) engaged in a selected physical therapy program, also besides, suit therapy training program while those in the group (B) received the same selected physical therapy program received by group (A) in addition to the whole-body vibration training program. The treatment programs were conducted three times per week for twelve successive weeks. Measurements obtained included bone mineral density at the lumbar spine as well as at the femoral neck. These measures were recorded pre- and post-treatment.Results:There was a significant improvement in favor of the whole-body Vibration group. Bone mineral density improved significantly at both the lumbar spine (P=.038) and the femoral neck (P=.005) in the WBV group as compared to the Suit therapy group.Conclusions:Whole-body vibration is effective in improving Bone Mineral Density rather than Suit therapy in children with cerebral palsy of spastic diplegia.     

Effects of aging on bone mineral content and bone biomarkers in female cynomolgus monkeys.

Age-related changes in bone mineral content and bone biomarkers were assessed over the complete lifespan of female cynomolgus monkeys. The bone mass of the lumbar spine increased linearly from birth to about 2.5 years of age, and this increase gradually slowed thereafter until a peak bone mass was achieved at 9 years of age. The bone mass stabilized after 9 years of age, showing no sign of further reduction with age. In contrast with the significant increase in bone mass before 2.5 years of age, significant decreases occurred in the serum concentrations of the following bone formation markers: intact osteocalcin, bone-specific alkaline phosphatase and amino-terminal propeptide of type I procollagen, but the serum concentration of carboxy-terminal propeptide of type I procollagen did not change significantly throughout the entire lifespan. Concerning the bone resorption markers, the levels of tartrate-resistant acid phosphatase fluctuated throughout the entire lifespan. The skeleton of an aging female monkey undergoes changes similar to those observed in senescent humans, but did not undergo the menopausal changes seen in women. The use of female cynomolgus monkeys to model human skeletal interventions should therefore be undertaken with consideration of the similarities and differences between cynomolgus monkeys and humans.     

The relationship between the stiffness and the mineral content of bone

The modulus of elasticity (E) of bone increases very rapidly with increase in mineral content, and in this is atypical of most composite materials. It is proposed that this apparent anomaly is caused by the end-to-end fusion of apatite crystals as the matrix becomes saturated with mineral. There is electron microscopic evidence that this occurs. Calculations using a fairly simple model show that this mechanism could be effective in life.     

Effect of bone mineral density on masticatory performance and efficiency

doi: 10.1111/j.1741‐2358.2010.00414.x Effect of bone mineral density on masticatory performance and efficiency Objective: To evaluate the effect of bone mineral density (BMD) on masticatory performance and efficiency in dentate subjects. Background data: Osteoporosis is the most common disorder of the bone. It causes reduction in BMD of the all the skeletal tissue including jaw bones. It also promotes bone loss in jaw bones. In osteoporosis, a reduction of maximal bite force and greater electromyography activity of masticatory muscles is documented. This may lead to the development of masticatory dysfunction which can be assessed by a chewing test in the form of change in masticatory performance and efficiency. Materials and methods: Sixty subjects with equal numbers of men and women were selected for the study, in which BMD screening (T‐score) was carried out to identify the normal, osteopenic and osteoporotic subjects. Their masticatory performance and efficiency was evaluated by a chewing test (fractional sieving method). Results: A high ‘T’ score was associated with low masticatory efficiency and a low ‘T’ score with high masticatory efficiency. Masticatory performance and efficiency was significantly higher among males as compared to females with similar range of BMD. Conclusion: In both genders, high BMD groups (low ‘T’ score) had a significantly high percentage of masticatory efficiency compared to the low BMD (high ‘T’ score) group.     

Effect of CaSO4 and NaCl on mineral content ofLeucaena leucocephala

The effects of varying CaSO₄ and NaCl levels on the nutrient content ofLeucaena leucocephala were established by examining the concentrations of Na, Ca, Cl, K and Mg in leucaena roots, stems and leaves. Leucaena was grown in nutrient solution at four levels of CaSO₄ (0.5, 1.0, 2.5 and 5.0 mM) and NaCl (1, 25, 50 and 100 mM), in randomized blocks with five replications. Leucaena excluded sodium from stems and leaves when NaCl concentration was 50 mM or less. Sodium uptake decreased as CaSO₄ concentration increased. Calcium uptake was affected by NaCl concentration when substrate CaSO₄ concentration was 0.5 mM. At this level, 100 mM NaCl caused a marked decrease in leaf calcium and a marked increase in leaf Cl. In all other treatments, Cl uptake was not affected by CaSO₄ concentration. Potassium uptake was strongly depressed as NaCl concentration increased at low Ca concentration, but this effect was offset at high Ca. Magnesium uptake decreased as CaSO₄ levels increased.     

Measurement of bone mineral content in vivo using photon absorptiometry

Progress in evaluating treatment of systemic bone disease has been hampered in the past by lack of precise in vivo quantitative techniques. Recently a method has been developed for measurement of bone mineral content (BMC), based on bone absorption of low-energy monochromatic radiation. This paper discusses a technique of photon absorptiometry using ¹²⁵l as a collimated point source. The technique is simple, with accuracy and precision within 2%.BMC and bone width (W) were measured in the distal radius of 359 normal subjects ranging in age from 5 to 82 years. A “normal” curve of BMC/W with age as the independent variable was then obtained from this population and was constructed for each sex. A positive correlation of BMC/W with height and body weight was found in a group of normal males.A series of patients with osteoporosis or malabsorption, or undergoing hemodialysis or steroid treatment, was then assessed in order to demonstrate changes in BMC/W that may occur secondary to disease or disturbances in calcium metabolism. Many of these patients were found to have a BMC/W below the normal mean value for their age and sex.     

Effect of growth hormone therapy on IGF-I, bone GLA-protein and bone mineral content in short children with and without chronic renal failure.

Chronic renal failure (CRF) in the young is complicated by, among other conditions, growth retardation, hyperparathyroidism and uremic osteodystrophy. Many children with CRF are now being treated with growth hormone (GH). Since GH has a direct mitogenic effect on osteoblasts in culture, we studied the effects of GH therapy on osteoblastic activity, such as serum alkaline phosphatase (AP), bone GLA-protein (BGP) and bone mass density (BMD) in poorly growing children with and without CRF. Fifteen (4 girls, 11 boys) healthy children with short stature (SS) and 10 (3 girls, 7 boys) children with end-stage renal failure (CRF) 4.5-12.4 years of age were treated with daily subcutaneous injections of GH in a dose of 0.1-0.125 IU/kg/day for 1 year. IGF-I, BGP and BMD of the spine were determined before and after the year of treatment. During GH therapy, a similar increase in height velocity and IGF-I were noted in SS and CRF groups: 3.8 +/- 0.77 to 8.38 +/- 1.25 (p < 0.001) vs. 4.0 +/- 0.6 to 7.14 +/- 1.3 cm/year (p < 0.001) and 7.8 +/- 2.6 to 21.8 +/- 7.5 (p < 0.01) vs. 7.9 +/- 1.3 to 21.5 +/- 5.6 nmol/l (p < 0.01), respectively. AP increased from 205 +/- 27 to 274 +/- 50 IU/l (p < 0.01) in the SS group but not in CRF patients (223 +/- 58 pre- 218 +/- 51 IU/l post-GH therapy).(ABSTRACT TRUNCATED AT 250 WORDS)     

Tensile behavior of cortical bone: dependence of organic matrix material properties on bone mineral content

A porous composite model is developed to analyze the tensile mechanical properties of cortical bone. The effects of microporosity (volksman's canals, osteocyte lacunae) on the mechanical properties of bone tissue are taken into account. A simple shear lag theory, wherein tensile loads are transferred between overlapped mineral platelets by shearing of the organic matrix, is used to model the reinforcement provided by mineral platelets. It is assumed that the organic matrix is elastic in tension and elastic-perfectly plastic in shear until it fails. When organic matrix shear stresses at the ends of mineral platelets reach their yield values, the stress-strain curve of bone tissue starts to deviate from linear behavior. This is referred as the microscopic yield point. At the point where the stress-strain behavior of bone shows a sharp curvature, the organic phase reaches its shear yield stress value over the entire platelet. This is referred as the macroscopic yield point. It is assumed that after macroscopic yield, mineral platelets cannot contribute to the load bearing capacity of bone and that the mechanical behavior of cortical bone tissue is determined by the organic phase only. Bone fails when the principal stress of the organic matrix is reached. By assuming that mechanical properties of the organic matrix are dependent on bone mineral content below the macroscopic yield point, the model is used to predict the entire tensile mechanical behavior of cortical bone for different mineral contents. It is found that decreased shear yield stresses and organic matrix elastic moduli are required to explain the mechanical behavior of bones with lowered mineral contents. Under these conditions, the predicted values (elastic modulus, 0.002 yield stress and strain, and ultimate stress and strain) are within 15% of experimental data.     

Total body bone mineral and pelvis bone mineral content as parameters of bone mass in men. A dual-energy X-ray absorptiometry study.

Total body bone mineral content (TBBM) is a highly discriminating determinant of bone mass. We correlated TBBM with pelvis bone mineral content (PBMC) and pelvis bone mineral density (PBMD) in 179 normal men, in order to observe whether the pelvis is an adequate region of bone mass evaluation. There was a good correlation between PBMC and TBBM (r = 927, p less than 0.001), and significant correlations between PBMD and TBBM (r = 818, p less than 0.001) and between PBMC and PBMD (r = 0.902, p less than 0.001). As the pelvis does not undergo the densitometric changes so often observed in the spine, we believe that the pelvis is appropriate as anatomic region for bone mass evaluation studies.     

Effect of bed rest immobilization on metabolic turnover of bone and bone mineral density

Immobilization induces abnormal bone metabolism and severe decalcification of bone. To investigate the effect of middle-term immobilization on bone metabolism, we studied 10 young healthy males and females during bed rest for 20 days. Bone mineral density (BMD) rapidly decreased in both lumbar and metacarpal bones. No bone showed consistent BMD alterations, partial increase and partial decrease, and both lumbar and metacarpal bone showed similar rapid BMD change. Urinary excretion of pyridinoline tended to slightly increase by day 10, and to decline by day 20 (mean +/-SE: 34.2 +/-7.4, 26.3+/-4.6 nmol day-1, respectively). Neither alkaline phosphatase (isoform III) nor tartrate-resistant acid phosphatase, changed, suggesting that in the early stage of immobilization bone matrix in some part might increase or be resorbed without any activation of osteoblast or osteoclast, resulting in rapid calcification or decalcification, respectively.     

Annual changes in bone mineral content and body composition during growth

OBJECTIVES: To compute the annual changes in total bone mineral content (BMCt), lean tissue mass and fat mass (LTM and FM) during growth. METHODS: Whole body DXA data were used to calculate the annual changes of the parameter P (P = BMCt, LTM or FM), as a percentage, as DeltaP% = 100 x (P(i+1) - P(i)) / P(i); with P(i) and P(i+1) the values for P at age i and age (i+1). Smoothed curves were then obtained from DeltaP% values plotted against age. RESULTS: Changes in FM were different in males and females. A peak velocity was marked for the three tissues at age 6.5 in boys, and at age 6.5-7.5 in girls; a pubertal peak spurt appeared at age 12 in girls and between age 13 and 14 in boys. This latter peak was followed by an exponential decrease, and no significant changes were found for the three components after age 20 in girls and age 21-22 in boys. CONCLUSION: Changes in tissue accretion during growth are easy to follow when expressed in percentages. Fat changes, especially, should be around 17% in girls and 15% in boys at the age of puberty.     

Influence of calcitonin treatment on the bone structure and mineral content in osteoarthritis.

8 femoral heads removed in 4 patients operated on by bilateral total hip replacement for osteoarthritis were evaluated. 3 patients were treated with Calcitonin between the first and the second operation. X-ray powder diffractometry analysis showed an improvement of bone crystallinity in the Calcitonin treated patients.     

Extreme obesity reduces bone mineral density: complementary evidence from mice and women

Objective: To evaluate the effects of body adiposity on bone mineral density in the presence and absence of ovarian hormones in female mice and postmenopausal women. Research Methods and Procedures: We assessed percentage body fat, serum leptin levels, and bone mineral density in ovariectomized and non‐ovariectomized C57BL/6 female mice that had been fed various calorically dense diets to induce body weight profiles ranging from lean to very obese. Additionally, we assessed percentage body fat and whole body bone mineral density in 37 overweight and extremely obese postmenopausal women from the Women's Contraceptive and Reproductive Experiences study. Results: In mice, higher levels of body adiposity (>40% body fat) were associated with lower bone mineral density in ovariectomized C57BL/6 female mice. A similar trend was observed in a small sample of postmenopausal women. Discussion: The complementary studies in mice and women suggest that extreme obesity in postmenopausal women may be associated with reduced bone mineral density. Thus, extreme obesity (BMI > 40 kg/m²) may increase the risk for osteopenia and osteoporosis. Given the obesity epidemic in the U.S. and in many other countries, and, in particular, the rising number of extremely obese adult women, increased attention should be drawn to the significant and interrelated public health issues of obesity and osteoporosis.