Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0024523 (malabsorption)
 7,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Severe osteomalacia of uncertain etiology was observed in a 44-year-old woman. There was no evidence of chronic renal insufficiency, malabsorption, or of the renal tubular defects classically associated with osteomalacia. However, the dietary history suggested vitamin D deficiency and most of the biochemical findings were compatible with this condition. The unusual feature of the case was a decrease in plasma bicarbonate levels which appeared to be due to a lowered renal tubular threshold for bicarbonate reabsorption. There was no renal tubular defect with respect to hydrogen ion excretion.Rapid symptomatic and radiologic improvement occurred when the dietary intake of vitamin D was increased to approximately 200 I.U. per day and the acidosis was simultaneously corrected with sodium bicarbonate. Although no firm conclusions could be drawn about the relative importance of vitamin D deficiency or chronic acidosis in the production of the osteomalacia, the possibility that the chronic acidosis may have been a major contributing factor is discussed.
 ...
PMID:Osteomalacia associated with renal bicarbonate loss. 594 Jun 37

Proximal muscular weakness is a feature of many metabolic bone diseases but is not well recognized in spinal osteoporosis. Thirty-six post-menopausal women presenting with back pain, with or without osteoporosis, were therefore studied in order to define the relationship between abnormal electromyographic findings and disturbed vitamin D metabolism, as both low plasma 1,25 dihydroxy vitamin D concentrations and malabsorption of calcium have been reported in osteoporosis. Patients with abnormal electromyograms had lower concentrations of plasma 1,25 dihydroxy vitamin D (mean 78.3 pmol/l, SD 20.5, n = 15) than normal subjects of similar age (mean 110.4 pmol/l, SD 39.4, n = 21; P less than 0.01), but electromyographic abnormality was not associated with changes in radiocalcium absorption, plasma 25 hydroxy vitamin D, plasma calcium or phosphate or urinary calcium or hydroxy-proline excretion or impaired renal function. There was no relationship between abnormal electromyography and osteoporosis assessed by spinal radiographs and iliac crest biopsy. These findings are consistent with our previous suggestion that muscle weakness in many unrelated bone disorders is related to low plasma 1,25 dihydroxy vitamin D concentrations, but suggest that there is no relationship between proximal myopathy and spinal osteoporosis in post-menopausal women.
 ...
PMID:Vitamin D metabolites in post-menopausal women and their relationship to the myopathic electromyogram. 622 23

These studies were performed to see if jejunal malabsorption of magnesium in patients with chronic renal disease was influenced by therapy with 1 alpha, 25-dihydroxyvitamin D3 [1,25-(OH)2D3; 2 microgram/day by mouth for 7 days]. This treatment restored normal serum concentrations of the vitamin D metabolite from 0.9 +/- 0.2 to 4.2 +/- 0.6 ng/dl. Jejunal absorption of magnesium, measured by a triple-lumen constant-perfusion technique, was enhanced in each of the seven patients by this therapy. The mean value rose from 0.04 +/- 0.02 to 0.13 +/- 0.02 mmol . 30 cm-1 . h-1. This last value is similar to the magnesium absorption rate in untreated normal subjects. These results demonstrate that magnesium absorption in the human jejunum is dependent on vitamin D, and they show that 1 alpha,25-dihydroxyvitamin D3 therapy in patients with chronic renal failure is associated with an enhanced jejunal absorption of magnesium.
 ...
PMID:Effect of 1,25-(OH)2D3 on jejunal absorption of magnesium in patients with chronic renal disease. 624 8

Vitamin D deficiency is in most cases subclinical and can only be detected by blood vitamin assays or biochemical changes in phosphorus and calcium metabolism. Clinical and radiological osteomalacia is much less common. It is due to prolonged and profound hypovitaminaemia, which in turn depends upon a variety of factors, the main one being defective photosynthesis. Low vitamin D dietary intake apparently does not result in osteomalacia unless it is accompanied by insufficient exposure to sun. Malabsorption of cholecalciferol results from steatorrhoea of various origina. Disorders in hepatic 25-hydroxylation are due to drug enzymatic induction and seem to be unrelated to the state of the renal function. Disorders in renal 1,25-hydroxylation may be consecutive to reduced renal tissue, impaired stimulation, or inhibiton or even congenital lack of 1-alpha hydroxylase.
 ...
PMID:[Osteomalacia due to vitamin D deficiency. Part One: mechanisms (author's transl)]. 625 Jan 30

The absorption of simultaneously administered equimolar doses of 14C vitamin D3 and 3H 25 hydroxyvitamin D3 (25-OH-D3) has been studied in controls and patients with a variety of gastrointestinal disorders. As assessed from peak radioactivity in the serum and from faecal excretion of radioactivity, malabsorption of both vitamin D3 and 25-OH-D3 occurred in patients with steatorrhoea. Malabsorption of vitamin D3 was greater than 25-OH-D3. The magnitude of malabsorption of these compounds was related to the severity of the steatorrhoea but was moderate enough to suggest that replacement therapy in patients with intestinal malabsorption should be accomplished with relatively small doses of vitamin D. The more potent vitamin D metabolites are probably unnecessary in this situation.
 ...
PMID:Comparative absorption of vitamin D3 and 25-hydroxyvitamin D3 in intestinal disease. 625 63

Elucidation of the vitamin D endocrine system and the availability of potent metabolites have led to new approaches to vitamin D therapy. The traditional management of exogenous (sunlight) or endogenous (malabsorption) vitamin D deficiency without evidence of disordered vitamin D metabolism has not changed, since it consists of treatment with vitamin D itself--a therapy which preserves the normal intrinsic mechanisms for regulating the rate of production of 1,25-dihydroxycholecalciferol. 1,25-DHCC and the analogue compound 1 alpha-CC should be reserved for treatment of hypocalcemia consequent on chronic renal failure or hypoparathyroidism, where 1-hydroxylation is lacking or impaired. Hypophosphatemic rickets has been treated with 1-hydroxylated compounds, with promising results; this use of the latter metabolites warrants further investigation. The use of vitamin D metabolites and of pharmacological doses of vitamin D itself must be regarded as substitution of a hormone or hormone precursors. Therefore, careful monitoring of serum and urine calcium is required in every patient receiving these compounds, in order to avoid excessive dosage. Special attention must be paid to patients with sarcoidosis since they often develop hypercalcemia after vitamin D or UV-light exposure, as a result of an intrinsic regulation defect in 1,25-DHCC synthesis.
 ...
PMID:[Therapy with vitamin D and D-metabolites]. 626 26

The intestinal absorption of calcium (Ca) has been shown to depend on vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and dietary phosphorus (P) concentration. This study was designed to evaluate the role of dietary P independent of vitamin D3 or 1,25(OH)2D3. Vitamin D-deficient rats were studied during dietary P restriction and were compared with control groups raised on a normal-phosphorus diet (NP). Balance studies were sued. Net intestinal Ca absorption was significantly lower with dietary P restriction compared with the NP group. This malabsorption of Ca was corrected by the administration of either D3 for 1,25(OH)2D3, despite hypophosphatemia. Everted gut sacs showed a marked reduction in the uptake of 45Ca in the duodenum, jejunum, and ileum during dietary P restriction. We concluded that dietary P concentration plays a major role in intestinal Ca absorption in the vitamin D-deficient rats. These findings suggest an effect of the low-phosphate diet on the vitamin D-dependent, Ca-transport mechanism.
 ...
PMID:Intestinal absorption of calcium: role of dietary phosphate and vitamin D. 626 9

Five patients with primary biliary cirrhosis and vitamin D deficiency (serum 25-hydroxyvitamin D less than 6 ng/ml) are presented. All patients had low serum 24,25-dihydroxyvitamin D3 concentrations. Three patients had histological osteomalacia, negative calcium balance, and subnormal serum 1,25-dihydroxyvitamin D3. Malabsorption of a standard dose of [3H]vitamin D3 was found in three of four patients with steatorrhea, enabling the effective dose of vitamin D3 given to be calculated. Oral vitamin D3 400-4000 IU/day (effectively 400-1860 IU/day) resulted in a return to normal of the serum vitamin D metabolites, correction of the impaired intestinal calcium absorption and healing of the osteomalacia. Increases in serum calcium, phosphate, and the renal tubular reabsorption of phosphate occurred with a concomitant decrease in serum parathyroid hormone. It is suggested that osteomalacia in primary biliary cirrhosis is the end result of vitamin D deficiency; the hepatic and renal hydroxylations of vitamin D are normal and target tissues are responsive to endogenously produced metabolites of vitamin D.
 ...
PMID:Vitamin D deficiency, osteomalacia, and primary biliary cirrhosis. Response to orally administered vitamin D3. 629 63

Because of the high prevalence of metabolic bone disease in older persons, we investigated the possibility of impaired intestinal absorptive capacity for vitamin D3 in aging animals. Using a single-pass technique, we measured vitamin D absorption and mucosal accumulation in male rats 9 to 101 weeks of age. Intestinal length, water absorption, and vitamin D3 intestinal tissue concentration remained constant after 41 weeks of age. Vitamin D3 absorption increased from 1209 pmol/100 cm/hr at 9 weeks of age to 2114 pmol/100 cm/hr at 41 weeks of age and remained relatively constant thereafter. Because vitamin D3 absorption rate is partly regulated by the dimensions of the unstirred water layer, we assessed the dimensions of the UWL of our aging animals. As the animals aged, the surface area of the UWL increased from 197 to 316 cm2/100 cm, and its resistance decreased from 1.2 to 0.7 min/cm3/100 cm by 41 weeks of age and remained stable thereafter. Inasmuch as the UWL is a major regulatory step in the absorption of vitamin D, its constant dimensions after 41 weeks of age explain the normal absorption of vitamin D3 observed in our aging animals. If these findings are found to be true in humans as well, they would argue against the possibility of vitamin D3 malabsorption as a cause of metabolic bone disease seen in aging individuals.
 ...
PMID:Influence of aging on vitamin D absorption and unstirred water layer dimensions in the rat. 632 19

Therapy of the malabsorption syndrome centers on adequate diagnosis of the underlying pathology, with vigorous therapeutic efforts directed at correcting this and thereby preventing ongoing losses of nutrients. Dietary therapy includes a high-protein, high-calorie, low-fat diet often supplemented with MCTs in an effort to minimize steatorrhea. Water-soluble vitamin deficiency is rare, but supplementation with small daily doses is innocuous and probably should be prescribed. Significant fat-soluble vitamin deficiencies are seen more commonly and can be monitored by physical examination and the prothrombin time. Calcium, magnesium, and vitamin D deficiencies are more common than originally suspected. Adequate therapy requires monitoring of the serum calcium, magnesium, parathyroid hormone levels, and, optimally, 24-hour urinary collections for calcium. Supplementation of these mineral deficiencies requires ongoing close observation to prevent hypercalcemia. Iron deficiency can be easily diagnosed by available serum iron determination, and replacement with oral supplements is curative. Trace metal deficiencies occur, but our capabilities of detecting and treating them is still in its infancy. Figure 3 outlines our approach to the evaluation and treatment of the patients suspected of having the malabsorption syndrome.
 ...
PMID:Nutritional aspects of malabsorption syndromes. 641 33


<< Previous 1 2 3 4 5 6 7 8 9 10