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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Osteoporosis, a bone-thinning disease that leads to fractures, affects 25 million Americans, mostly women. The good news is that this disease is preventable and treatable. Adequate nutrition, for example, is estimated to reduce the impact of osteoporosis by as much as one half. The bad news is that unless more attention is given to communicating preventive strategies, osteoporosis and its related costs will continue to escalate. To make osteoporosis a priority among health professionals and communicators, The American Dietetic Association, in cooperation with National Diary Council, held a conference on this subject in November 1993. Recognized national experts addressed the issue of osteoporosis from various perspectives. This article summarizes the information presented at this conference. Prevention of osteoporosis focuses on increasing peak bone mass, which is usually reached between the age of 30 to 35 years, and reducing bone loss in later years. Bone health is influenced by three major interacting factors: diet, exercise, and estrogen. To optimize bone health, accumulating scientific findings support intakes of calcium and vitamin D exceeding current Recommended Dietary Allowances (RDAs) for these nutrients. Unfortunately, most women in the United States, in particular female adolescents, do not consume the RDA for calcium. Although recommendations to prevent osteoporosis can be made, there are several obstacles to translating these recommendations into action. Examples include failure to inspire people to make lifestyle changes early in life and to provide understandable recommendations. To be facilitators of change and not just nutrition experts, dietitians and other health professionals need to overcome these obstacles and to effectively market the risks of and prevention strategies for osteoporosis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Osteoporosis: visions for care and prevention--a conference report. 819 63

We recently reported that mice treated with 1,25-dihydroxyvitamin D3 ( 1,25-(OH)2D3) or 19-nor-1,25-(OH)2D2 experienced a severe loss of their thymocytes and decreased proliferation in response to concanavalin A mitogen. The present study investigated the effect of short-term treatment with 1,25-(OH)2D3 on the thymic architecture and thymocyte subsets. Daily treatment with 1,25-dihydroxyvitamin D3 at 20 ng per mouse for 4 days induced significant involution of thymic tissue. The atrophy was predominantly observed in the cortical component. Flow cytometric analysis of thymocyte subsets showed that the CD4 + CD8 + population was the primary target. Since the treated mice experienced profound hypercalcemia, we studied the effect of 1,25-(OH)2D3 on animals fed a vitamin D-deficient, low calcium diet or the same diet containing vitamin D for 25 days prior to treatment. The low calcium fed mice showed severe hypocalcemia and slight thinning of thymic cortex. Treatment with 1,25-(OH)2D3 moderately improved the hypocalcemia but had no further effect on the thymus of these animals. On the other hand, hypercalcemia and thymic atrophy were found in the animals fed the diet containing vitamin D. Overall, the atrophy effect on the thymus caused by 1,25-(OH)2D3 treatment was prevented by eliminating the hypercalcemia observed in + D + Ca treated animals. Thus, thymic atrophy probably resulted from hypercalcemia and not from 1,25-(OH)2D3 itself.
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PMID:Effect of 1,25-dihydroxyvitamin D3 on mouse thymus: role of extracellular calcium. 860 Sep 85

Bone thinning causing both fractures and severe pain not associated with fractures has been recognized in patients with chronic liver diseases. The patients most commonly affected are those with primary or secondary biliary cirrhosis, but those with alcoholic liver disease and cirrhosis after active chronic hepatitis may also be involved. Chronic liver disease has also been recognized as an important cause of osteoporosis in both sexes, with the mechanism thought to be a combination of calcium and/or vitamin D. The 9.1% patients with chronic active hepatitis accompanied with osteodystrophy. But 50% cirrhotic patients accompanied with osteodystrophy. Bone densitometry was determined by Digital Image Processing Method (Osteodystrophy < mean-2SD: age- and sex-matched normal value). Serum levels of osteocalcin (BGP) and parathyroid hormone (PTH) in patients of hepatic cirrhosis without osteodystrophy were lower than those with osteodystrophy. These results were suggested that hepatic osteodystrophy was rapidly turnover osteodystrophy. To function physiologically, vitamin D must be hydroxylation in liver to 25-(OH)-D and subsequently by the kidney to 1 alfa, 25-(OH)2-D. Osteodystrophy associated with hepatic cirrhosis is due to a defect in the 1 alfa-hydroxylation by the kidney rather than a hepatic hydroxylation defect. 1 alfa OH-D3 is very useful for treatment for hepatic osteodystrophy.
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PMID:[Hepatic osteodystrophy]. 964 89

For many years, osteoporosis has been considered as a women's disease. Data show that the incidence of this bone thinning disease is high in men. Aging is accompanied with changes in circulating hormone levels. Thus, low testosterone levels is associated with osteoporosis in men. Like osteoporosis in females, in men, might be treated with calcium supplements, vitamin D and bisphosphonates. Recent report of treatment for osteoporotic men with bisphosphonate alendronate was successful in improving bone density at several sites in the male skeleton, in reducing the incidence of fractures and in preventing loss of height. The benefits and risks of hormone androgen replacement therapy in men are not fully defined, but the androgens supplementation is also expected to have favorable consequences on bone.
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PMID:[Osteoporosis in males is a frequently overlooked risk]. 1072 10

The mechanisms behind the influence of PHPT on the skeleton are closely connected with bone turnover. Throughout life, the skeleton is continuously renewed by bone remodeling, a process which serves the purpose of repairing damaged bone and adapting the skeleton to changes in physical load. In this process, old bone is removed by osteoclastic resorption and new bone is laid down by osteoblastic formation. Bone mass increases with growth in the first decades of life, and around the age of 30 years the peak bone mass is reached. Thereafter, as a result of mechanisms involving bone remodeling, a net bone loss is seen: 1) A reversible bone loss because of increase in the remodeling space, i.e., the amount of bone resorped but not yet reformed during the remodeling cycle. This mechanism leads to decrease in average trabecular thickness and cortical width, and to increase in cortical porosity. 2) An irreversible bone loss caused by negative bone balance, where the amount of bone formed by the osteoblasts is exceeded by the amount of bone resorbed by the osteoclasts at the same remodeling site. Consequently, progressive thinning of trabecular elements, reduced cortical width and increased cortical porosity is seen. 3) Finally, perforation of trabecular plates by deep resorption lacunae leads to complete irreversible removal of structural bone components. Parathyroid hormone, together with vitamin D, are the principal modulators in calcium homeostasis. The main actions of PTH are executed in bone and kidneys. In the kidneys, PTH increases the tubular re-absorption of calcium, thereby tending to increase serum calcium. PTH also induces increased conversion of 25(OH)-D to 1,25(OH)2-D. This last action, enhances intestinal calcium absorption and increased skeletal calcium mobilization, which further adds to the circulating calcium pool. In bone, the "acute" regulatory actions of PTH on serum calcium are probably accompliced via activation of osteocytes and lining cells. A second mechanism of PTH in bone is the regulation of bone remodeling. The action seems to be an increased recruitment from osteoblastic precursor cells and activation of mature osteoclasts. It is supposed that these responses are predominantly mediated indirectly through actions on osteoblast-like or nonosteoblast-like stromal cells, as osteoclasts themselves to not have PTH receptors. Bone metabolism and bone mass are studied by biochemical bone markers, bone histomorphometry, and densitometry. As bone markers and bone histomorphometry give information on bone metabolism from different points of view, these methods are preferably combined. Histomorphometry gives detailed information about bone turnover on cellular level, the whole remodeling sequence is described, and the bone balance can be calculated. However, they focus on a small volume, and may, therefore, not be representative for the whole skeleton. On the other hand, studies of bone markers supply general information about turnover in the whole skeleton, but they do not give facts on the bone turnover on the cellular or tissue level and bone balance. Bone densitometry is the principal method in studying bone mass, but valuable information concerning bone structure also comes from histomorphometry. Bone remodeling is considerably increased in PHPT. Studies of bone markers show increase in both resorptive and formative markers, and the increases seem to be of equivalent size. This is in agreement with histomorphometric findings and shows that the coupling between resorption and formation is preserved. By histomorphometry on iliac crest biopsies, trabecular bone remodeling is found increased by 50%, judged by the increase in activation frequency; a measure of how often new remodeling is initiated on the trabecular bone surface. In PHPT, such remodeling activity is repeated about once every year. Reconstruction of the whole remodeling sequence does not show major deviations in lengths of the resorptive and formative periods compared to normal. Furthermore, the amount of bone removed by the osteoclasts during the resorptive phase is matched by the amount of new bone formed by the osteoblasts leading to a bone balance very close to zero. Compared with trabecular bone, the turnover rate in cortical bone is considerably lower, around 10%. Remodeling of the cortical bone takes place at the endocortical, the pericortical, and the Haversian surfaces. Endocortical bone remodeling activities are very similar to trabecular remodeling activities with good correlation between individual parameters. Periosteal remodeling activity is negligible in PHPT, as it is in the normal state. Cortical porosity, which reflects the remodeling activity on the Haversian surface, is increased by 30-65% in PHPT. (ABSTRACT TRUNCATED)
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PMID:The skeleton in primary hyperparathyroidism: a review focusing on bone remodeling, structure, mass, and fracture. 1141 22

Glucocorticoids are important drugs in the treatment of variety diseases, but long-term period use can lead to various adverse effects, including osteoporosis. Glucocorticoid-induced osteoporosis is mainly caused by inhibition of osteoblastic bone formation, which results not only in decreased bone mineral density, but reduction of bone strength by trabecular thinning in bone microstructures. The evidence suggests that daily oral glucocorticoid doses higher than 5 mg prednisolone or equivalent increase the risk of fracture within 3-6 months after the start of therapy. High-dose inhaled glucocorticoids may also increase fracture risk. The diagnostic procedures are similar to those for primary osteoporosis, but the diagnostic threshold for bone mineral density needs to be higher than that for primary osteoporosis. Treatment with vitamin D, calcitonin, sex hormone replacement, and bisphosphonates has been shown to be effective, and bisphosphonates have been demonstrated to be the most valuable drugs for glucocorticoid-induced osteoporosis. There are several lines of evidence indicating that they are effective in preventing and treating low bone mineral density and in reducing fracture risk.
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PMID:Glucocorticoid-induced osteoporosis. 1551 6

Vitamin D is synthesized in skin through a reaction mediated by sunlight, and it is metabolized to 25-hydroxyvitamin D, in liver, and in 1,25-dihydroxyvitamin D, in kidney. This last reaction has a tight feedback mechanism. 1,25-dihydroxyvitamin D is the active hormone, and its actions are mediated mainly by nuclear receptors. Its major functions are in calcium metabolism and bone mass maintenance. Hypovitaminosis D, as a disease in adult people, manifests itself with hypocalcemia and secondary hyperparathyroidism with subsequent loss of trabecular bone, thinning of cortical bone, and, eventually, a higher risk of fractures. Hypovitaminosis D is a very common condition in Europe, Africa, North America and some South American countries, such as Chile and Argentina. Measurement of serum total 25-hydroxyvitamin D concentration is the gold standard to diagnose vitamin D deficiency. Serum concentrations below 50 nmol/L are associated with an increase in parathyroid hormone concentration, and bone loss. Risk factors for vitamin D deficiency, like poor sunlight exposition, aging skin and factors that interfere with normal vitamin D metabolism, are well established. Oral vitamin D supplementation, an easy and inexpensive treatment, is needed to treat this illness.
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PMID:[Vitamin D deficiency in adults: to better understand a new presentation of an old disease]. 1662 72

Klotho gene mutation leads to a syndrome strangely resembling chronic kidney disease patients undergoing dialysis with multiple accelerated age-related disorders, including hypoactivity, sterility, skin thinning, muscle atrophy, osteoporosis, vascular calcifications, soft-tissue calcifications, defective hearing, thymus atrophy, pulmonary emphysema, ataxia, and abnormalities of the pituitary gland, as well as hypoglycemia, hyperphosphatemia, and paradoxically high-plasma calcitriol levels. Conversely, mice overexpressing klotho show an extended existence and a slow aging process through a mechanism that may involve the induction of a state of insulin and oxidant stress resistance. Two molecules are produced by the klotho gene, a membrane bound form and a circulating form. However, their precise biological roles and molecular functions have been only partly deciphered. Klotho can act as a circulating factor or hormone, which binds to a not yet identified high-affinity receptor and inhibits the intracellular insulin/insulin-like growth factor-1 (IGF-1) signaling cascade; klotho can function as a novel beta-glucuronidase, which deglycosylates steroid beta-glucuronides and the calcium channel transient receptor potential vallinoid-5 (TRPV5); as a cofactor essential for the stimulation of fibroblast growth factor (FGF) receptor by FGF23. The two last functions have propelled klotho to the group of key factors regulating mineral and vitamin D metabolism, and have also stimulated the interest of the nephrology community. The purpose of this review is to provide a nephrology-oriented overview of klotho and its potential implications in normal and altered renal function states.
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PMID:Klotho: an antiaging protein involved in mineral and vitamin D metabolism. 2241 41

Although alveolar wall thinning has been attributed to apoptosis of interstitial lung lipofibroblasts (LFs), the underlying molecular mechanism(s) remains unknown. Although the physiological vitamin D steroid hormone 1alpha,25(OH)(2)D(3) (1,25D) has been suggested as a local paracrine/autocrine effector of fetal lung maturation and is known to affect fibroblast apoptosis, its effects on LF apoptosis are unknown. We determined the role of 1,25D and its metabolite, C-3-epimer (3-epi-1,25D), on LF and alveolar type II (ATII) cell differentiation, proliferation, and apoptosis. Embryonic day 19 Sprague-Dawley fetal rat lung LFs and ATII cells were treated with 1,25D or 3-epi-1,25D (1 x 10(-10) to 1 x 10(-8) M) for 24 h, and cell proliferation, apoptosis, and differentiation were assessed. Both 1,25D and 3-epi-1,25D exhibited dose-dependent increases in expression of the key homeostatic epithelial-mesenchymal differentiation markers, increased LF and ATII cell proliferation, and decreased apoptosis. Furthermore, rat pups administered 1,25D from postnatal days 0 to 14 showed increased expressions of key LF and ATII cell differentiation markers, increased Bcl-2-to-Bax ratio as an index of decreased spontaneous alveolar LF and ATII cell apoptosis, increased alveolar count, and a paradoxical increase in septal thickness. We conclude that spatial- and temporal-specific actions of vitamin D play a critical role in perinatal lung maturation by stimulating key alveolar epithelial-mesenchymal interactions and by modulating LF proliferation/apoptosis. These data not only provide the biological rationale for the presence of an alveolar vitamin D paracrine system, but also provide the first integrated molecular mechanism for increased surfactant synthesis and alveolar septal thinning during perinatal lung maturation.
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PMID:1alpha,25(OH)2D3 and its 3-epimer promote rat lung alveolar epithelial-mesenchymal interactions and inhibit lipofibroblast apoptosis. 1957 20

Vitamin D plays a major role in mineral and skeletal homeostasis through interaction with the nuclear vitamin D receptor (VDR) of target cells. Recent reports have indicated that some cellular effects of vitamin D may occur via alternative signaling pathways, but concrete evidence for mineral homeostasis has not been shown in vivo. To investigate this issue, the actions of calcitriol (1,25D) and maxacalcitol (OCT), which were developed for treatment of uremia-induced secondary hyperparathyroidism, were analyzed in VDR knockout (VDR(-/-)) mice. The VDR(-/-) mice were fed a rescue diet immediately after weaning. 1,25D, OCT or a control solution was administered intraperitoneally to these mice three times a week for eight weeks. Biological markers and bone growth were measured and bone histomorphometric analysis of the calcein-labeled tibia was performed 24 h after the final administration. Significantly higher levels of serum Ca(2+) were observed in 1,25D- and OCT-treated mice, but the serum parathyroid hormone level was unchanged by both agents. Impaired bone growth, enlarged and distorted cartilaginous growth plates, morphological abnormalities of cancellous and cortical bones; a morbid osteoid increase, lack of calcein labeling, and thinning of cortical bone, were all significantly improved by 1,25D and OCT. The significance of these effects was confirmed by bone histomorphometrical analysis. Upregulation of the calbindin D(9k) mRNA expression level in the duodenum may explain these findings, since this protein is a major modulator of Ca transport in the small intestine. We conclude that 1,25D and OCT both at a high dose exert significant effects on Ca and skeletal homeostasis with the principal improvement of Ca status in VDR(-/-) mice, and some of these effects may occur through an alternative vitamin D signaling pathway.
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PMID:Improvement of impaired calcium and skeletal homeostasis in vitamin D receptor knockout mice by a high dose of calcitriol and maxacalcitol. 1963 78


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