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Biomedical subjects

R B Mazess

Publications and source records attributed to R B Mazess.

At least 127 records · Page 7Linked to original sources
PubMed1983

Long-term influence of calcitriol (1,25-dihydroxyvitamin D) and supplemental phosphate in X-linked hypophosphatemic rickets.

Ten patients with hypophosphatemic rickets (eight with X-linked familial form) were treated with vitamin D2 (10,000 to 75,000 units per day) and oral phosphate (1.5 to 3.6 gm) for a total of 438 treatment months. Therapy was then changed to calcitriol (17 to 34 ng/kg/day) and the same phosphate dose. Patients served as their own controls, and significant biochemical changes noted were an increase in immunoreactive parathyroid hormone from 29 +/- 9 (SD) microliters Eq/ml (pre-phosphate) to 62 +/- 34 on vitamin D2 plus PO4, then decreasing to 40 +/- 20 on a regimen of 1,25-dihydroxyvitamin D (1,25(OH)2D) plus PO4; serum PO4 rose from 2.44 +/- 0.45 (SD) mg/100 ml to 3.06 +/- 0.79 and then to 3.43 +/- 0.76; alkaline phosphatase activity decreased from 677 +/- 298 (SD) IU/liter to 457 +/- 183 to 290 +/- 176. Serum calcium and creatinine levels were unchanged. Both urinary calcium excretion and calcium-creatinine ratio decreased after therapy with 1,25(OH)2D. Urinary phosphate excretion was higher after calcitriol administration. Serum 1,25(OH)2D levels were low in these vitamin D2-treated patients, and an inverse relationship between serum 25(OH)D and 1,25(OH)2D was found. Improved bone mineralization was evident from serial assessment by photon absorptiometry, and radial bone mineral content rose from 75.3% +/- 2.2% of expected to 82.2% +/- 1.4% (P less than .005). Stature was improved when assessed by standard deviation for chronologic age but did not reach statistical significance. Long-term 1,25(OH)2D plus phosphate therapy appears to be more efficacious than vitamin D2 in this form of rickets, particularly in improving phosphate homeostasis.

Adolescent↗
PubMed1982

Skeletal demineralization in Turner's syndrome.

The bone mineral status of 17 girls with Turner's syndrome was evaluated by single photon absorptiometry. Bone mineral content (BMC) was 25.4% below that predicted by normalization for age, sex, height, weight, and bone width. Only 25% of this demineralization could be attributed to delayed skeletal maturation. Bones of girls who received estrogen replacement therapy were less demineralized than those of the others. The bone mineral deficit became less pronounced with advancing age. It could not be determined if the apparent effect of estrogens was related to age or if the apparent improvement with age was really due to an effect of estrogen treatment. For 8 subjects followed longitudinally there was no significant change in the BMC deficit.

Adolescent↗
PubMed1982

Bone status of children receiving anticonvulsant therapy.

Bone mineral status was assessed by direct photon absorptiometry on 140 children and adolescent hospital outpatients receiving long-term anticonvulsant drug therapy and on 132 institutionalized mentally retarded subjects, 74 of whom were receiving anticonvulsant drugs. Serum calcium, phosphorus and alkaline phosphatase concentrations were determined for the hospital outpatients. Average deviations of bone mineral content (%BMC) ranged from 8.4-16.2% of normal values predicted from regression analysis. A trend toward increased demineralization was associated with length of anticonvulsant drug therapy. Mentally retarded subjects and hospital subjects with seizures accompanied by other serious disorders showed significantly greater osteopenia than hospital subjects with seizures alone. A lack of association of BMC with presence of anticonvulsant drug therapy in the mentally retarded population suggested that their low %BMC values were due to other factors related to the nature of the sample and the condition of institutionalization. Biochemical values showed a lack of association with osteopenia. A comparison of the present results on compact bone with results of others involving osteoid of trabecular bone suggests that anticonvulsant drug therapy affects these tissues differently and that the chemistry of the blood more closely reflects the osteoid proliferation of the trabecular bone rather than the changes related to the osteopenia of compact bone.

Adolescent↗
PubMed1982

Circulating vitamin D metabolite concentrations in childhood renal diseases.

Vitamin D metabolites were measured in children, untreated with glucocorticoids, who had renal disease. Two groups were defined in relation to endogenous creatinine clearance values: those with impaired clearance , 0 to 48 ml/min per 1.73 m2; and those with unimpaired clearance, 75 to 150 ml/min per 1.73 m2. Serum 1.25(OH)2D was 16 +/- (SD) 12 pg/ml in impaired patients (N=24) and 48 +/- 16 pg/ml in unimpaired patients (N=18). The latter level is not different from healthy childhood controls (43 +/- 12 pg/ml; N=194). Serum samples of 25(OH)D2 and D3 were comparable in each group and not different from control values of 33.2 +/- 10.3 ng/ml. Serum 24,25(OH)2D was 0.6 +/- (SD) 0.14 ng/ml in patients with a clearance of less than 13 ml/min per 1.73 m2, 1.39 +/- 0.54 ng/ml in those with a clearance of 18 to 48 ml/min per 1.73 m2, and 152 +/- 0.91 ng/ml in patients without an impairment of clearance. Only patients with the lowest clearance had values different from control values of 1.70 +/- 0.57 ng/ml. In our study we suggest that a significant reduction in 24,25(OH)2D and 1,25(OH)2D are found at low clearance values in children with tubulointerstitial disease. Our study further suggests that a reduction in renal tubular mass is important in accounting for these changes in vitamin D metabolite values.

24,25-Dihydroxyvitamin D 3↗
PubMed1982

Changes in bone mineral density of the proximal femur and spine with aging. Differences between the postmenopausal and senile osteoporosis syndromes.

We measured bone mineral density (BMD) of the proximal femur, lumbar spine, or both by dual photon absorptiometry in 205 normal volunteers (123 women and 82 men; age range 20 to 92 yr) and in 31 patients with hip fractures (26 women and 5 men; mean age, 78 yr). For normal women, the regression of BMD on age was negative and linear at each site; overall decrease during life was 58% in the femoral neck, 53% in the intertrochanteric region of the femur, and 42% in the lumbar spine. For normal men, the age regression was linear also; the rate of decrease in BMD was two-thirds of that in women for femoral neck and intertrochanteric femur but was only one-fourth of that in women for lumbar spine. This difference may explain why the female/male ratio is 2:1 for hip fractures but 8:1 for vertebral fractures. The standard deviation (Z-score) from the sex-specific age-adjusted normal mean in 26 women with hip fracture averaged -0.31 (P < 0.05) for the femoral neck, -0.53 (P < 0.01) for the intertrochanteric femur, and +0.24 (NS) for the lumbar spine; results were similar for 5 men with hip fractures. By contrast, for 27 additional women, ages 51-65 yr, with only nontraumatic vertebral fractures, the Z-score was -1.92 (P < 0.001) for the lumbar spine. Thus, contrary to the view that osteoporosis is a single age-related entity, our data suggest the existence of two distinct syndromes. One form, "postmenopausal osteoporosis," is characterized by excessive and disproportionate trabecular bone loss, involves a small subset of women in the early postmenopausal period, and is associated mainly with vertebral fractures. The other form, "senile osteoporosis," is characterized by proportionate loss of both cortical and trabecular bone, involves essentially the entire population of aging women and, to a lesser extent, aging men, and is associated with hip fractures or vertebral fractures or both.

Adult↗
PubMed1982

On aging bone loss.

A survey was done of aging changes in compact and trabecular bone. During the past decade, noninvasive methods have demonstrated similar results for compact bone in large samples. Aging decreases of 3%/decade begin at about age 40 in both sexes and continue, but in women, an additional loss occurs after menopause, bringing their total rate of decrease to 9%/decade between ages 45 and 75. Results on trabecular bone loss are more variable, the majority indicating a slightly lower rate of loss (6% to 8% decade), beginning in young adulthood (20 to 40 years) in both sexes. These findings suggest that the common assumption about a large ongoing loss of trabecular bone after menopause may be erroneous. These assumptions are examined, as are the implications of the findings for calcium metabolism, anatomical correlations and fracture incidences.

Adult↗
PubMed1981

Total body bone mineral and lean body mass by dual-photon absorptiometry. I. Theory and measurement procedure.

A method was developed for measuring total body bone mineral (TBBM) and lean body mass in vivo using dual-photon absorptiometry. The entire body was scanned in a rectilinear raster (transverse speed of 1 cm/s and longitudinal steps of 2.5 cm) with a modified nuclear medicine scanner and conventional nuclear counting electronics. The source was 153Gd (1 Ci) with principal photopeaks at 44 and 100 keV. The scan time was about 70 min with an absorbed dose of under 1 mrem. The low dose allows measurements to be repeated at frequent intervals or used on children. Short-term (months) precision of TBBM was about 1.5% for isolated skeletons and about 2% on normal human subjects. Long-term (years) precision on skeletons was under 3%. The precision of percent fat was 0.9%, which would lead to an error of less than 1% in the TBBM. Geometry of measurements also had minimal (and correctable) influence on the accuracy of results. The accuracy (1 standard error of estimate) of TBBM on isolated skeletons (N = 5) was 36 g (equivalent to about 13 g of Ca) with a correlation coefficient of 0.99; this error amounts to about 1--1.5% in normal adults; 2% in older women, and 2.5% in osteoporotic females. The dual-photon absorptiometry method could be implemented in many nuclear medicine departments to follow skeletal changes during growth and aging or to follow the course of a disease or treatment.

Body Composition↗
PubMed1981

Total body bone mineral and lean body mass by dual-photon absorptiometry. II. Comparison with total body calcium by neutron activation analysis.

Total body bone mineral (TBBM) was measured in vivo using dual-photon absorptiometry (DPA) in 10 subjects. The total body calcium (TBCa) was measured in the same subjects using neutron activation analysis. The correlation between the two methods was very high (r greater than 0.99) and the standard error of estimate was low. The TBCa relative to TBBM was about 39%. The two noninvasive methods provided nearly identical indications of skeletal mass, but the radiation exposure with DPA was 500 to 5000 times smaller (0.6 mrem vs 300 to 3000 mrem). The radius shaft bone mineral content was highly correlated with the TBBM (0.97) and the TBCa (0.98) and could be used to estimate the latter variables with errors (1 SEE) of 9% and 6%, respectively.

Body Composition↗
PubMed1981

Total body bone mineral and lean body mass by dual-photon absorptiometry. III. Comparison with trunk calcium by neutron activation analysis.

Dual-photon absorptiometry using 153Gd (44 and 100 keV) was used to measure the bone mineral content (BMC) of the trunk and of the total body (TBBM) in 7 volunteers with no overt bone disease. These values were compared to those obtained with partial-body neutron activation of calcium (trunk Ca). The trunk Ca seemed to represent best a 60 x 30 cm area; the correlation coefficient with the corresponding BMC in that area was 0.97 (SEE congruent to 7%). Trunk Ca was also highly correlated with TBBM (r = 0.96; SEE = 8%) and with radius BMC (r = 0.92; SEE = 11%), but the correlations with the BMC of smaller subareas of the trunk were lower (r congruent to 0.9; SEE approximately 12%). The BMC of the lumbar spine was only moderately correlated with trunk Ca, radius BMC and TBBM (r approximately 0.82; SEE approximately 18%), and only slightly more associated with trunk BMC (r approximately 0.88; SEE approximately 14%). The BMC of the combined lumbar-thoracic spine showed higher correlations with trunk Ca, radius BMC and TBBM (r approximately 0.87; SEE approximately 13%), and trunk BMC (r = 0.93; SEE approximately 10%). An accurate and sensitive measure of spinal status requires a direct measurement of that area.

Adult↗
PubMed1981

Osteopenia in juvenile diabetes.

The bone mineral status of fifty-one children with diabetes mellitus was studied by single photon absorptiometry. The mean bone mineral content was 13% below values predicted by age, sex, height, and weight. Those children whose diabetes was one year or less in duration were as osteopenic as those whose diabetes was of longer duration. The demineralized children received a higher daily insulin dose than others. No association was noted between the degree of skeletal demineralization and sex, statural growth, renal function, and serum calcium and phosphorus. No significant changes in bone mineral content were noted longitudinally.

Child↗
PubMed1981

Differential changes in bone mineral density of the appendicular and axial skeleton with aging: relationship to spinal osteoporosis.

Patterns of bone loss in the axial and the appendicular skeleton were studied in 185 normal volunteers (105 women and 82 men; age range, 20--89 yr) and in 76 women and 9 men with vertebral fractures due to osteoporosis. Bone mineral density was measured in vivo at the lumbar spine (predominantly trabecular bone) by dual photon absorptiometry and at the midradius (greater than 95% cortical bone) and distal radius (75% cortical and 25% trabecular bone) by single photon absorptiometry. In normal women, bone diminution from the vertebrae began in young adulthood and was linear. In the appendicular skeleton, bone diminution did not occur until age 50 yr, was accelerated from aged 51 to 65 yr, and then decelerated somewhat after age 65 yr. Overall bone diminution throughout life was 47% for the vertebrae, 30% for the midradius, and 39% for the distal radius. In normal men, vertebral and appendicular bone diminution with aging was minimal or insignificant. Mean bone mineral density was lower in patients with osteoporosis than in age- and sex-matched normal subjects at all three scanning sites, although spinal measurements discriminated best; however, there was considerable overlap. By age 65 yr, half of the normal women (and by age 85 yr, virtually all of them) had vertebral bone mineral density values below the 90th percentile of women with vertebral fractures and, thus, might be considered to have asymptomatic osteoporosis. For men, the degree of overlap was less. The data suggest that disproportionate loss of trabecular bone from the axial skeleton is a distinguishing characteristic of spinal osteoporosis.

Adult↗
PubMed1981

Long-term therapy of uremic osteodystrophy in adults with calcitriol.

Patients with end-stage renal failure develop osteodystrophy in part due to defective production of 1,25-dihydroxycholecalciferol by the kidney. We treated eight adults with chronic renal failure and osteodystrophy with 1,25-dihydroxycholecalciferol (calcitriol) for 30-44 months. Seven of these patients were also symptomatic with bone pain and/or muscle weakness. Striking amelioration of muscle weakness occurred, and bone pain was considered to be significantly improved in four of seven patients. Hypercalcemia was noted in all the patients, necessitating a reduction in the daily dose of calcitriol to a range of 0.125 to 0.5 microgram/day. While serum alkaline phosphatase fell during therapy, serum iPTH did not show any significant change. Bone mineral content improved in four patients, though it still remained below normal. Radiographic changes of osteodystrophy showed definite improvement in only three.

Adult↗