Bone mass measurement by DXA: influence of analysis procedures and interunit variation.

Interunit variability among bone densitometers is due to different factors, including different calibration procedures and algorithms and variability in photon source energies and/or intensities. Other factors, such as the choice of scan parameters or the analysis procedures, can also introduce variability. The new generation of dual-energy x-ray absorptiometry (DXA) has partially improved this situation. The aim of this study was to investigate the operator-dependent analysis procedures that can affect scan results and to evaluate the phantom and in vivo interunit variation of some DXA instruments. Four DXA instruments (QDR 1000 and 1000/W, Hologic, Inc.) were used. Potential sources of variability in the analysis procedures of anteroposterior lumbar spine and hip scans were considered: in most cases these procedures significantly influenced scan results. On lumbar spine, an enlargement of the scan window of less than 3 cm was responsible for an average increase in bone mineral density (BMD) of about 3%. On the hip, lowering the scan window by about 1 cm accounted for an increase in the whole-segment BMD of about 4%. After standardization of analysis procedures, interunit and intraunit coefficients of variation and percentage differences among instruments were less than 1% for all the parameters considered (area and bone mineral content and density) with both an anatomic and a geometric phantom, and in nine subjects scanned by two different devices the percentage difference in BMD was greater than 2%. This study shows that present interunit variability allows comparisons among laboratories, but only if highly standardized analysis procedures are used.

Age, time since menopause, and body parameters as determinants of female spinal bone mass: a mathematical model.

The study of mathematical models to describe bone mass behavior throughout life is a possibility for assessing the main factors of peak bone mass and bone loss. We developed a mathematical model to predict spinal bone mass behavior on a sample of 181 healthy Italian women whose lumbar bone mineral content was determined by Gd-153 dual photon absorptiometry. This model proved to be both efficient, showing the best fit (r = 0.7 on spinal bone mineral content) when compared to other previously suggested models, and also reliable as its fit remained the best when applied to a subsequent sample of 519 women whose lumbar spine was measured by dual X-ray photon absorptiometry. This model suggests that body height and body weight (but not age) are determinants of bone mass in premenopausal women. In postmenopausal women, an accelerated phase of bone loss starting at menopause is dependent on age and time since menopause, whereas body mass index acts as a protective factor. This model confirms the influence on spinal bone mass not only of age and time since menopause but also of body size parameters.

Spinal and forearm bone mass in relation to ageing and menopause in healthy Italian women.

Most studies concerning bone status have been performed in Nordic and Anglo-Saxon countries and few data are available on southern European populations. We performed a cross-sectional study on spine and forearm bone mass in 234 healthy Italian women and related the results to age and time since menopause. Forearm bone mass does not decline in premenopausal age, whereas, as far as the spine is concerned, a significant reduction appears 3 years before the mean age of menopause; in both cases, the occurrence of menopause accounted for an accelerated phase of bone loss. In postmenopausal women both spine and forearm bone mass show a stronger correlation with years since menopause than with age. According to a linear exponential model, the rate of spinal bone loss per year since menopause is around 4% in the first 3 years which slows down to around 2% in the 5th year; the corresponding rates of forearm bone loss are 2% and 1.3%, respectively.

Cyclic hormonal replacement therapy after the menopause: transdermal versus oral treatment.

In an open, randomized, comparative, between-patient trial, 45 postmenopausal women were treated for 4 months with cyclical transdermal oestradiol 0.05 mg per day or oral conjugated equine oestrogens 0.625 mg per day, in both cases, plus, medroxyprogesterone acetate 10 mg per day on the last 8 days of each cycle. Similar relief from postmenopausal symptoms was obtained with both treatments. Post-treatment histological evaluation of the endometrium did not reveal neoplastic or hyperplastic change in any patient. Early follicular-phase plasma oestradiol levels were observed only after transdermal oestradiol. There was a significant reduction in serum total cholesterol and LDL cholesterol in both treatment groups, with no difference between treatments, whereas serum triglyceride levels were decreased only by transdermal oestradiol. Plasma calcium and phosphorus fell significantly and serum intact parathyroid hormone rose significantly, with no difference between the therapies. No significant changes were observed in clotting factors. Transdermal oestradiol appears to be an effective and safe hormonal replacement therapy, and this route of administration may be responsible for the more useful action of the drug on serum lipids and plasma oestradiol levels.

Bone metabolism in juvenile rheumatoid arthritis.

Plasma and urinary indexes of bone metabolism were studied in 36 children affected by juvenile rheumatoid arthritis (JRA) during 1 year, in order to evaluate the calciotropic hormone levels and bone mass. Children were divided in three groups according to the subtype of JRA: pauciarticular, polyarticular, systemic. Patients of the latter two groups were on corticosteroid treatment. A control group of healthy children (matched for age and sex) was compared. Children affected by pauciarticular disease did not show any difference with respect to controls. In the polyarticular and systemic groups, basal observation revealed decreased levels of 25(OH)D, significantly lower (P less than 0.01) with respect to the control and pauciarticular groups. After one year, 25(OH)D showed a further decrease in the systemic group, while PTH levels were increased. Moreover, bone mineral density values in systemic JRA were significantly lower than values of a matched control group and did not increase as expected during the year. It seems thus possible that severe JRA has an influence on bone mass, perhaps mediated by a decrease in active vitamin D metabolites.

Bone mineral density in adult celiac patients and the effect of gluten-free diet from childhood.

Peripheral single photon absorptiometry was used to measure forearm bone mineral density in 22 celiacs on gluten-free diet from childhood (male 14, female 8, age 13-20) and 29 untreated adult celiacs at diagnosis (male 5, female 24, age 18-56, 14 with subclinical disease), compared with healthy sex- and age-matched controls. Bone mineral density was similar in patients treated from childhood and their controls [(668.4 +/- 65.3 vs. 654.9 +/- 69.6 mg/cm2, (mean +/- SD)], but significantly lower in untreated patients than in their controls (598.3 +/- 83.1 vs 673.2 +/- 42.7 mg/cm2, p less than 0.001). It was also significantly lower in the 12 younger untreated celiacs (18-28 yr) versus controls (619.4 +/- 68.5 vs 669.1 +/- 39.3 mg/cm2, p less than 0.01). In the untreated women, but not their controls, a negative correlation (p less than 0.05) was observed between bone mineral density and age. Bone mineral density did not correlate with severity of clinical or biochemical abnormalities. These results suggest that bone derangements are common in celiacs diagnosed in adulthood, even if they never presented evident malabsorption symptoms, and emphasize the importance of early diagnosis and treatment.

Vitamin D metabolites in spasmophilia.

The comparison of 20 untreated spasmophilic patients (2 men, 18 women) with 25 healthy subjects revealed no significant differences in vitamin D metabolite plasma levels or in other laboratory indexes of calcium metabolism except for ionized and cytosolic free calcium levels which were lower in the former group (P less than 0.01; P less than 0.001). After 3 months treatment with calcitonin and 25-hydroxyvitamin D there was a clear improvement in patient symptoms, no significant modification of 1,25-dihydroxyvitamin D levels and significant increases in 25-hydroxyvitamin D, cytosolic free calcium and urinary calcium (P less than 0.001, P less than 0.001 and P less than 0.01, respectively). We conclude that high plasma levels of 25-hydroxyvitamin D play an important role in restoring normal cytosolic free calcium levels and reducing clinical manifestations in spasmophilia.

Bone involvement in primary hemochromatosis and alcoholic cirrhosis.

Biochemical indexes of bone metabolism, bone mineral density, and histomorphometry were evaluated in 14 male patients with noncholestatic cirrhosis due to primary hemochromatosis (six cases) or to chronic alcohol abuse (eight cases), and in 30 male controls of similar age. Alkaline phosphatase in alcoholic patients was significantly higher than in controls (mean +/- SD 50.4 +/- 33.7 vs 33.0 +/- 7.1 U/L, p less than 0.01), as was urinary hydroxyproline in both hemochromatotics and alcoholics (mean +/- SD, 44.3 +/- 8.4 and 40.4 +/- 16.8, respectively, vs 30.1 +/- 4.5 mg/g, p less than 0.001 and p less than 0.005). Bone mineral density was significantly lower in hemochromatotics than in alcoholics and controls (mean +/- SD, 591 +/- 90 vs 765 +/- 87 and 759 +/- 34 mg/cm2, respectively, p less than 0.005 and p less than 0.001). At bone biopsy, trabecular osteoporosis was observed in two hemochromatotics and four alcoholics, and osteomalacia was seen in another alcoholic. Overall densitometric and histomorphometric findings indicate a derangement of trabecular bone in both alcoholic and hemochromatotic cirrhosis, whereas cortical osteoporosis seems limited to hemochromatotic patients.

Growth in young children with chronic renal failure.

Statural growth and its relation to growth potential, renal function, blood urea nitrogen (BUN), mineral metabolism hormones and dietary intake were studied in 17 prepubertal children (aged 1.6-9.3 years) on conservative treatment for chronic renal failure due to tubulo-interstitial nephropathy. Statural growth (height SDS) was related to the degree of renal failure, was more retarded than ossification, and was independent of the chronological age of the patients. We observed that the lower the glomerular filtration rate (GFR), the lower was the growth potential (increased bone age/statural age ratio). Growth velocity may be normal regardless of statural and bone maturation delay and the degree of renal insufficiency. Impaired growth rate correlated with parathyroid hormone levels, caloric intake and increased blood urea nitrogen during the year of observation. These data show that comprehensive monitoring and suitable treatment must be performed in order to prevent growth retardation at any GFR level.

Bone and mineral metabolism in adult celiac disease.

Bone mineral density (125I photon absorptiometry) was lower in 20 untreated adult celiac patients than in sex- and age-matched controls (p less than 0.001), and plasma alkaline phosphatase, parathyroid hormone, urinary hydroxyproline/creatinine levels were higher than normal (p less than 0.05, less than 0.001, less than 0.05, respectively). Gluten-free diet was started, and the patients were divided randomly into two treatment groups, one which received oral 25-hydroxyvitamin D 50 micrograms/day and one which did not. After 12 months' treatment, bone turnover markers showed a decrease, which did not reach statistical significance, and bone mineral density did not show significant modifications compared with base line in either group. It was found that a gluten-free diet followed for 1 yr can prevent further bone loss, but no significant differences were detected between the two groups.

Increased forearm bone mineral content after bromocriptine treatment in hyperprolactinemia.

We studied 15 hyperprolactinemic women to evaluate possible modifications of bone mineral content after pharmacological treatment. Patients received a dopamine agonist (bromocriptine) for six months after which there was a significant decrease of prolactin plasma levels (P less than 0.01) and a significant increase of bone mineral content (P less than 0.05).