Biomedical subjects

A Vaswani

Publications and source records attributed to A Vaswani.

At least 19 recordsLinked to original sources

PubMed1998

Discordance between ultrasound of the calcaneus and bone mineral density in black and white women.

Black women have 40% of the incidence rate for hip fracture and have a higher bone mineral density (BMD) than white women. The possibility was raised that bone quality may be disproportionately greater than the advantage in bone density in protection against osteoporotic fractures in black versus white women. Ultrasound (US) of the calcaneus is believed to measure properties of bone in addition to its density. We performed bone density measurements and US of the calcaneus in 108 black and 177 healthy white women, aged 20-70 years. The highest correlation was seen between total body bone density and speed of sound (r = 0.75). The interracial differences in BMD were all statistically significant and varied from 3.4 to 7.6%. The US measurements had lesser interracial differences than the bone density measurements, with velocity barely different between races. These findings suggest that US of the calcaneus measures properties of bone different from density. Fracture prediction data using US from prospective data in white women should not be extrapolated to black women because of the discordance between bone density and US measurements. Prospective studies are needed comparing US measurements in black women to the occurrence of osteoporotic fractures.

Adult↗

PubMed1998

Relationship of body water compartments to age, race, and fat-free mass.

Water compartments were studied in 72 black and 128 white women, aged 20 to 70 years. Total body water (TBW) was measured by tritiated water dilution, and extracellular water (ECW) was measured by using delayed gamma neutron activation for the determination of total body chloride. Intracellular water (ICW) was assessed as the difference between TBW and ECW. Fat-free mass (FFM) was estimated by the measurement of total body potassium (TBK) and total body fat (TBF) by measurement of total body carbon (TBC). Total body protein was calculated from total body nitrogen (TBN). TBW was found to decline with age and to also be significantly influenced by body size. The extracellular water space was 41.5% of TBW. The decline of TBW with age is due primarily to a decline in ICW. The hydration of the FFM increased with age for the overall population because of a decline in TBK and TBN and an increase in ECW. Body composition models that have assumed constancy of hydration should be adjusted not only for gender but for age and body size.

Adipose Tissue↗

PubMed1997

Comparison of body composition in black and white premenopausal women.

We examined 23 pairs of black and white premenopausal women to determine whether there were ethnic differences in body composition. The pairs were matched on weight and height. Each woman had measurements of total body water taken by a tritiated water dilution technique, total body nitrogen, and total body carbon by neutron-activation, mineral ash by dual x-ray absorptiometry, and body potassium by whole body counting. Differences between blacks and whites were compared with the use of both the two-compartment and four-compartment models. The two-compartment model showed that in premenopausal black and white women of similar age, heights, and weights, blacks had significantly more lean mass. The four-compartment model resulted in similar conclusions. The black women had larger protein, mineral, and water compartments and less fat than whites. It may be that body weight measurements as an indicator of obesity should be adjusted for black versus white women.

Absorptiometry, Photon↗

PubMed1997

Thyroid disease among the Rongelap and Utirik population--an update.

In 1954, 253 Marshallese were accidentally exposed to fallout radiation from the hydrogen bomb, BRAVO. The Marshall Islands Medical Program (MIMP) was established by the Department of Energy in 1955 to monitor and treat radiation-related disease pursuant to this accident. Medical teams from Brookhaven National Laboratory, a federal institution, regularly visit the Marshall Islands to give medical care to the exposed population. The most significant complication of the exposure has been found to be thyroid disease due to the ingestion of radioactive iodides from the fallout. In 1963 the first thyroid nodules were found in Rongelap subjects and in 1969 in Utirik. Non-neoplastic adenomatous nodules were associated with higher doses of radiation and neoplastic nodules developed in individuals receiving lower doses of radiation. Women were more susceptible to the development of palpable thyroid nodules than men. In 1994 the MIMP initiated examination of the thyroid by ultrasound to supplement the clinical examination. One hundred and sixty-four patients were evaluated. No significant differences were found in the incidence of thyroid nodules or the mean nodule count between the three groups of Rongelap and Utirik exposed and a comparison patient population. There was no significant difference in the incidence of thyroid nodules in males vs. females. Five exposed patients were referred for surgical excision of a nodule detected only by ultrasound. These ultrasound findings are unexpected in that females are known to have a higher incidence of thyroid disease than males and we expected that the incidence of ultrasound nodules would be higher in the exposed population.

Biopsy, Needle↗

PubMed1997

Sodium distribution in black and white women.

Delayed gamma neutron activation analysis (DGNA) was performed on 99 black and 168 healthy white women, aged 20-80 years, to examine sodium distribution in the two ethnic groups. Elements measured included total body levels of sodium (TBNa) and chlorine (TBCl). The black women were heavier, and consequently had a higher body surface area. Sodium excess (Naes) was calculated from TBNa and TBCl. Total body water was measured by tritiated water dilution. TBNa was higher in black than white women, and this difference persisted when the values were corrected for body surface area. TBNa and Naes declined significantly with age in white women, whereas extracellular fluid sodium (ECFNa) remained constant. The change with age was not statistically significant in black women for TBNa, Naes or ECFNa. Our sample of healthy black women had a higher TBNa and Naes than healthy white women. This difference persisted after adjustment for body surface area, so that values for sodium distribution need to be adjusted for race. The change in TBNa with age in white women appears to be due to their decline of skeletal tissue mass with a consequent decline in nonexchangeable sodium.

Adult↗

PubMed1996

Risk for osteoporosis in black women.

Models of involutional bone loss and strategies for the prevention of osteoporosis have been developed for white women. Black women have higher bone densities than white women, but as the black population ages there will be an increasingly higher population of black women with osteoporosis. Strategies should be developed to reduce the risk of black women for fragility fractures. Dual energy X-ray absorptiometry measurements of the total body, femur, spine, and radius were performed on 503 healthy black and white women aged 20-80 years. Indices of bone turnover, the calcitrophic hormones, and radioisotope calcium absorption efficiency were also measured to compare the mechanisms of bone loss.The black women had higher BMD values at every site tested than the white women throughout the adult life cycle. Black women have a higher peak bone mass and a slightly slower rate of adult bone loss from the femur and spine, which are skeletal sites comprised predominantly of trabecular bone. Indices of bone turnover are lower in black women as are serum calcidiol levels and urinary calcium excretion. Serum calcitriol and parathyroid hormone levels are higher in black women and calcium absorption efficiency is the same in black and white women, but dietary calcium intake is lower in black women. Black and white women have a similar pattern of bone loss, with substantial bone loss from the femur and spine prior to menopause and an accelerated bone loss from the total skeleton and radius after menopause. The higher values for bone density in black women as compared with white women are caused by a higher peak bone mass and a slower rate of loss from skeletal sites comprised predominantly of trabecular bone. Low-risk strategies to enhance peak bone mass and to lower bone loss, such as calcium and vitamin D augmentation of the diet, should be examined for black women. The risk vs. benefits of hormonal replacement therapy should be determined, especially in older women.

Adult↗

PubMed1996

Differential effects of dietary calcium augmentation and hormone replacement therapy on bone turnover and serum levels of calcitrophic hormones.

The mechanism of action of retardation of postmenopausal bone loss may be different for dietary calcium augmentation and hormonal replacement therapy (HRT). We performed a three-arm, placebo-controlled, randomized clinical trial comparing an intake of calcium of 1700 mg with: (1) calcium augmentation with HRT and (2) placebo. One hundred and eighteen women entered the study; 17 patients dropped out of the study. The vast majority of women were less than 2 years postmenopause. Bone mineral density declined significantly in the placebo group. The previously reported rates of change in the HRT group were significantly positive for total body calcium and the trochanter and not significantly different from zero for the others. The rate of change in the calcium augmentation group was intermediate between that in the two other groups, and achieved statistical significance compared with placebo for the total body calcium measurement and for the neck of the femur. Measurements were made prior to treatment and at the end of the study (2.9 years +/- 1.1 SD) for parameters of bone turnover and the calcitrophic hormones, to examine whether the mechanism of action was different for calcium augmentation versus hormonal therapy. There were no changes in the placebo group. The calcium augmentation group had a significant increase in 24-h urinary calcium and declining values for urinary collagen cross-links (pyridinium and deoxypyridinium), urinary hydroxyproline and calcitriol. The group treated with HRT and dietary calcium augmentation also had an increase in urinary calcium and a decline in collagen cross-links and urinary hydroxyproline and skeletal alkaline phosphatase; serum calcitriol did not change. The HRT group also displayed a drop in serum osteocalcin, and an increase in nephrogenous cAMP. Serum parathyroid hormone remained unchanged in all groups. Dietary calcium augmentation retards postmenopausal bone loss by decreasing resorption. The addition of HRT results in a more marked decline in bone resorption parameters and a suppression of parameters of bone formation. Whereas calcium augmentation suppressed calcitriol levels, the addition of HRT resulted in maintenance of calcitriol levels, possibly through enhancement of the renal effects of parathyroid hormone, although other mechanisms are possible.

Bone Density↗

PubMed1996

Aging in women--the four-compartment model of body composition.

The four-compartment model of body composition was examined in 155 white women through measurement of total body carbon (TBC), nitrogen (TBN), calcium (TBCa), and water levels. The age (mean +/- SD) of the population was 51.4 +/- 13.5 years, and values for the four compartments were as follows (in kilograms): protein 8.9 +/- 1.0, water 30.9 +/- 3.5, mineral 2.6 +/- 0.4, and fat 22.6 +/- 7.3. There was a linear change with age for protein and water, whereas mineral and fat were curvilinear. These latter two compartments also showed differences in premenopausal and postmenopausal rates of change. Various models were fit to the data to adjust for body size and age. Each of the four compartments (mineral, water, fat, and protein) changed with age, with fat increasing and the other compartments declining. The equation, y = age + age2 + height + weight, fit the data as well as the other models. Equations are provided to assess body composition in populations with disorders of nutrition, as well as other illnesses, using height, weight, and age as covariates. Since this was a cross-sectional study, longitudinal studies will have to be performed to confirm the accuracy of rates of change with age predicted with each compartment.

Absorptiometry, Photon↗

PubMed1996

Body composition in normal black women: the four-compartment model.

The four-compartment model of body composition was studied in 112 healthy black women to develop normative data to be used to assess deviations in illness. Each compartment was measured by an independent method: tritiated water dilution, prompt-gamma neutron activation analysis (for nitrogen), inelastic neutron scattering (for carbon) and dual energy x-ray absorptiometry (for calcium). The mean age of the population was 43.2 years. Race was self-declared. The mean values for the four compartments were [kg SE] protein: 9.6 (0.07); mineral 3.0 (0.03); fat 24.2 (0.70); and water 33.1 (0.29). Each of the compartments changed significantly with age (P < .0001). There were declines in total body water, mineral, and protein, whereas fat increased linearly with age. Linear regressions performed on pre- and postmenopausal women showed a significant difference only for the mineral compartment. Various models were fit to the data to adjust for body size and age. The equation y = age + height + weight fits the data as well as the other models. Equations and graphs were developed to assess each compartment using this linear model and may be used to assess the body composition status of healthy and ill black women. Although black women tended to be heavier than white women, after controlling for differences in body weight (and age) black women had a greater mass of protein, mineral, and water and a similar fat store. These differences, while statistically significant, were not of great magnitude. This was a cross-sectional study and suspected trends with aging must be confirmed by a longitudinal study.

Adipose Tissue↗

PubMed1995

The influence of menopause and hormonal replacement therapy on body cell mass and body fat mass.

OBJECTIVE: Our purpose was to determine the efficacy of dietary calcium augmentation in the prevention of early postmenopausal bone density loss in comparison with hormonal replacement therapy and placebo. STUDY DESIGN: A three-arm parallel randomized trial comparing the influence of placebo, dietary calcium augmentation, and estrogen-progesterone-calcium in 118 women who were within 6 years of menopause was conducted. Dual photon absorptiometry was performed annually to measure lean and fat mass. In addition, the ratio of fat in the trunk/extremities was measured. RESULTS: Body weight increased in each group. The increase was statistically significant in the hormone replacement group (0.8 kg/year). The percent of body fat increased in each group from baseline measurements, with the greatest increase in the hormonal replacement group. There was a decline in the extremity/trunk ratio in the hormonal replacement group as a result of a relatively greater increase in the trunk fat mass. There was a rapid rate of loss in lean body mass that was equal among groups. CONCLUSIONS: Menopause is associated with a gain in fat mass and a loss of lean body mass, but these changes in body composition are not prevented by hormone replacement therapy.

Adipose Tissue↗

PubMed1995

To what extent is bone mass determined by fat-free or fat mass?

One hundred sixty-four healthy black and white women aged 24-79 y were studied to determine to what extent bone mass is determined by fat-free mass (FFM). A multicomponent approach to body composition, with techniques that are not interdependent, was used. The measurements included dual x-ray absorptiometry (DXA), prompt gamma-neutron-activation analysis, inelastic neuron scattering, tritiated water dilution, and whole-body counting. Univariate correlations showed significant relationships of all the fat-free measures and most of the fat measures with bone mass measured by total body calcium (TBCa). Data from pre- and postmenopausal women were analyzed separately. The average FFM by itself explained 50-55% of the variability in TBCa whereas the average fat mass by itself explained only 5-18% of the variability. The contribution of fat mass was consistently greater in postmenopausal than in premenopausal women. When stepwise multiple regression with TBCa was performed to determine the influence of adding fat mass, height, and race to the relationship of FFM with TBCa, the variation explained by average FFM was 56% premenopausal, 50% postmenopausal; by height 3% premenopausal, 6% postmenopausal; by race 4% premenopausal, 8% postmenopausal; and average fat mass was not significant. Average values for fat mass and FFM were obtained by averaging all the methods used. In conclusion, in black and white healthy women, although bone mass may be partially influenced by fatness or race, the major determinant of bone mass is FFM. Fat mass may play a more important role in postmenopausal women.

Absorptiometry, Photon↗

PubMed1995

Comparative study of body composition by dual-energy x-ray absorptiometry.

UNLABELLED: Dual-energy x-ray absorptiometry (DEXA) is a readily available technique that has recently been applied to measurement of body composition. In order to validate this technique, results from DEXA were compared with fat-free mass (FFM) and fat mass (FM) measured by total body levels of potassium (TBK), nitrogen (TBN), water (TBW) and carbon (TBC). METHODS: A healthy population of 127 white women and 38 black women with a body mass index of 18-30 were recruited. RESULTS: Compared with each of the other methods, DEXA overestimated FM and underestimated FFM. The slopes of the FM by DEXA versus the FM from each of the four methods were approximately the same, with a s.e.e. ranging from 2.4 to 3.0 units. The slopes of DEXA in comparison to FFM, however, ranged from 0.61 to 0.74 and were significantly less than unity, with a s.e.e. of 1.6 to 2.4 units. CONCLUSION: These findings suggest that at high values of FFM, DEXA is measuring something different from the FFM measured by TBW, TBN and TBK. The program for separating bone and soft tissue and for separating soft tissue into fat and lean at higher values in the DEXA method may need to be adjusted.

Absorptiometry, Photon↗

PubMed1994

Calcium supplementation with and without hormone replacement therapy to prevent postmenopausal bone loss.

OBJECTIVE: To determine whether augmentation of dietary calcium is effective in the prevention of early postmenopausal bone loss. DESIGN: Three-arm, placebo-controlled, randomized parallel trial. The study duration was 2.9 +/- 1.1 (SD) years. SETTING: General community. PARTICIPANTS: 118 healthy, white women 3 to 6 years after spontaneous menopause, recruited by community announcement. INTERVENTIONS: Random allocation to daily intake of 1700 mg of calcium (calcium carbonate given in divided doses with meals); placebo; or conjugated equine estrogens (0.625 mg; days 1 to 25), progesterone (10 mg; days 16 to 25), and 1700 mg of elemental calcium daily. Each participant received 400 IU of vitamin D daily. MAIN OUTCOME MEASURES: Total body calcium measured by delayed gamma neutron activation analysis and whole-body counting; bone mineral density of the spine, femur, and radius measured by photon absorptiometry. RESULTS: Bone mineral density declined in the placebo group for the lumbar spine (-2.1%/y; 95% Cl, -3.3 to -0.9), femoral neck (-2.0%/y; Cl, -2.6 to -1.2), trochanter (-1.6%/y; Cl, -2.4 to -0.8), Ward triangle (-2.7%/y; Cl, -3.7 to -1.7), and total body calcium (-2.0%/y; Cl, -2.2 to -1.8). Rates of change were intermediate for calcium augmentation compared with placebo and estrogen-progesterone-calcium but statistically significant compared with placebo for total body calcium (-0.5%/y; Cl, -0.9 to -0.1; P = 0.006) and the femoral neck (-0.8%/y; Cl, -1.4 to -0.2; P = 0.03). CONCLUSIONS: Although less effective than estrogen-progesterone-calcium, calcium augmentation alone significantly retards bone loss from the femoral neck and improves calcium balance in recently postmenopausal women. Dietary calcium augmentation should be recommended as a strategic option in helping to prevent early postmenopausal bone loss.

Analysis of Variance↗

PubMed1992

Preferential osteopenia in women with osteoporotic fractures.

One-hundred thirty-six women with spontaneous vertebral crush fractures had bone density measurements by photon absorptiometry. Their absolute and relative extent of osteopenia were expressed as Z scores with respect to values from normal white women. Absolute Z scores were used to express the mean bone mass of women with crush fractures vis-a-vis normal women at peak bone mass; relative Z scores were used to express the same means vis-a-vis age-matched controls. The skeletal sites measured included the distal radius, lumbar spine, and three sites on the femur (neck, Ward's triangle, and trochanter). The absolute deficit for the five sites ranged from -1.66 to -2.60. The relative deficit was close to 1 SD for all sites. A discriminant analysis revealed that the spine and femur were predictive for vertebral crush fractures but the radius was not. Comparison with a previously reported hip-fracture population (n = 31) showed that the low bone density of the spine separated the two fracture groups best. We propose the following: (a) vertebral-fracture patients have extensive generalized osteoporosis including the hip with a preferential deficit in the spine and (b) hip-fracture patients have generalized osteoporosis with preferential osteopenia of the hip and do not have a greater mineral deficit in the spine or radius than age-matched normal women. It may be that if a single site is to be selected for screening for spine and hip fractures, the greatest value would be in measurement of the femur, although ideally the skeletal site of interest would be measured. Prospective studies are needed to confirm the utility of measurements at the spine and hip in prediction of future fractures.

Absorptiometry, Photon↗

PubMed1991

Coexisting hyperparathyroidism with thyrotoxicosis.

The coexistence of hyperparathyroidism complicating thyrotoxicosis is quite rare. We report the case of one patient who presented with thyrotoxicosis, (total thyroxine of 15.1 micrograms/dl (5-13), free thyroxine index of 18 (4-15) and triiodothyronine by RIA of 305 ng/dl (70-230) and asymptomatic hypercalcemia of 15 mg/dl (8.5-10.6), who was also initially noted to have an elevated (C-terminal) serum immunoreactive parathyroid hormone (iPTH) level of 8,800 pg/ml (50-340). With propylthiouracil and propranolol, however, this patient became normocalcemic with a decrease in iPTH values to 714 pg/ml. As the patient was tapered from medication, after being rendered euthyroid, a recurrence of hypercalcemia with rising iPTH levels occurred. PTH levels should be helpful in defining coexisting hyperparathyroidism in patients with thyrotoxicosis since in the latter iPTH is usually suppressed. Our findings support the recommendation that in patients suspected of having both hyperparathyroidism and hyperthyroidism, a diagnosis of the former can only be made with certainty after the patient has been rendered euthyroid with persistently elevated serum calcium and iPTH levels. While there are no clinical features which permit the easy identification of patients who present with dual lesions, the determination of iPTH values may be the most consistently helpful test initially, whereas other parameters such as vitamin D, serum phosphate are less reliable.

Adult↗

PubMed1991

Biochemical short-term changes produced by hormonal replacement therapy.

Seventy-one white women within 6 months to 6 years postmenopause were randomly assigned to three treatment groups: (a) placebo, (b) calcium, (c) cyclic estrogen-progestin plus calcium. Calcium was given as calcium carbonate with meals to attain an intake of 1,700 mg daily in the latter two groups. All women received 400 IU of vitamin D daily. Samples were obtained at baseline and after 2 months therapy. The hormonal treatment group had a decline in serum calcium, osteocalcin and urinary hydroxyproline and an increase in levels of calcitonin, parathyroid hormone and calcitriol. The increase in the latter two measurements could have resulted from the drop in serum calcium, it is also possible that the increase in calcitonin levels was a result of calcium supplementation. Although all these changes were statistically significant for the estrogen treatment group when considered alone, analysis of variance including the 3 groups demonstrated significance for the estrogen group for the parameters of skeletal metabolism but not for the changes in the calciotrophic hormones. There was an increase in serum calcium (p = 0.05) in the calcium augmentation group. It would be of interest to determine the effects of higher intakes of calcium in both the calcium and the estrogen treatment groups and to further explore differences in effects on bone remodeling between the two treatment approaches as well as the possibility of a additive effects. Early effects of estrogen replacement reduce bone remodeling whereas calcium supplementation to 1,700 mg per day of Ca CO3 did not appear to affect the parameters of bone remodeling.

Bone Remodeling↗

PubMed1990

Aging bone loss from the femur, spine, radius, and total skeleton.

In order to establish a comprehensive model for involutional bone loss, the following measurements were made of healthy white women: total body calcium by neutron activation analysis, bone density of the distal radius by single-photon absorptiometry, and dual-photon absorptiometry of the lumbar spine and femur (neck, Ward's triangle, and intertrochanteric areas). Longitudinal measurements were made for each of these skeletal sites except the femur. Evidence for a curvilinear component to the pattern of bone loss with aging was found for total body calcium and bone density of the radius, but not for the other measurements on analysis of cross-sectional data. Longitudinal studies confirmed that substantial bone loss begins only after menopause for the radius, whereas there is substantial premenopausal loss of bone from the lumbar spine. Prevention of vertebral osteoporosis requires maximizing bone mass before menopause. If longitudinal data confirm the model of linear rates of bone loss for the femur, there will be important implications for prevention of hip fractures.

Adult↗

PubMed1988

Calcitriol in the treatment of postmenopausal osteoporosis.

Calcitriol was compared with placebo in the treatment of postmenopausal osteoporosis in a double-blind, randomized, parallel clinical trial of 24 months' duration. Adjustment was made in dietary calcium to maximize the dose of calcitriol. The study was completed by 15 patients who received placebo and 12 patients who received calcitriol. The calcitriol group had positive slopes (compared with negative slopes for the placebo group) for total body calcium, bone mineral content of the radius, bone mineral density of the lumbar spine, and radiographic absorptiometry of the middle phalanges. The difference between the two groups was statistically significant for each of these measurements. The fracture rate in the treatment group was 250 per 1,000 patient-years as compared with 333 for the placebo group. The mean dose of calcitriol was 0.8 micrograms per day. Hypercalcemia, hypercalciuria, and perhaps nephrolithiasis were observed as complications of treatment. Calcitriol increased bone mineral density by decreasing bone resorption, but not by increasing bone formation. Future studies should concentrate on treatment with oral calcitriol in lower doses. It would also be of interest to examine parenteral administration of calcitriol. It is possible that bone formation can be increased by achieving higher serum levels of the drug, whereas complications may be avoided by using a non-oral route of administration.

Aged↗