Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Severe secondary hyperparathyroidism is still observed at present in 5-10% of haemodialysis patients. It requires surgical correction. Fifty-eight haemodialysis patients had neck surgery and their 222 parathyroid glands analysed. The individual gland weight was comprised between 22 and 3880 mg (mean +/- SEM, 689 +/- 62 mg). Mean total parathyroid gland weight per patient was comprised between 2 and 3 g. Schematically, 4 types of gland architecture could be distinguished: diffuse hyperplasia alone; diffuse hyperplasia associated with incipient nodule formation; hyperplasia with pronounced nodule formation; and nodule formations alone. Total gland weight was significantly higher for the latter two histological forms than for the former suggesting transformation with time of pure hyperplasia to nodular hyperplasia. Patients with chronic pyelonephritis had a mean gland weight higher than that of patients with chronic glomerulonephritis (3308 +/- 498 mg versus 1824 +/- 358 mg, p less than 0.01). No relation was found between total gland weight and plasma calcium, phosphate or alkaline phosphatases. However, a weak relation existed between total gland weight and plasma immunoreactive parathyroid hormone. In addition, a negative relation was observed between highest prior plasma aluminium and gland weight when considering only patients with a gland weight less than 2000 mg. Parathyroid gland aluminium content was significantly higher in haemodialysis patients than in nonuraemic patients with primary hyperparathyroidism. A direct relation was found between parathyroid gland and bone aluminium. In conclusion, in haemodialysis patients with evolving hyperparathyroidism initially diffuse gland hyperplasia appears to be associated progressively with nodule formation. Circulating immunoreactive parathyroid hormone is positively related to total gland weight.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:[Hyperparathyroidism secondary to renal insufficiency: anatomo-clinical relations and the potential role of an aluminum overload]. 648 74

Fifty-eight patients on intermittent haemodialysis underwent parathyroidectomy because of severe secondary hyperparathyroidism. Mean individual parathyroid gland weight was 689 +/- 62 (SEM) mg. Mean total gland weight per patient was between two and three grams. Increasing nodule formation within hyperplastic glands appeared to develop with increasing time of duration of hyperparathyroidism. Patients with chronic pyelonephritis had a higher gland weight than those with chronic glomerulonephritis. A direct relationship was found between gland weight and circulating immunoreactive parathyroid hormone, but an inverse relationship between gland weight and plasma aluminium concentration. The higher the parathyroid gland aluminium, the higher was the bone aluminium concentration.
 ...
PMID:Secondary hyperparathyroidism in chronic haemodialysis patients: a clinico-pathological study. 665 93

Several renal functions respond to nephron loss by a compensatory adaptation. Whether the production of 1,25(OH)2D3 also adapts to a renal mass reduction is still a matter of controversy. In the present study we have investigated in rats the influence of unilateral nephrectomy, in both the acute (48 hr) and chronic (2 to 6 weeks) state, on plasma 1,25(OH)2D3 level measured by competitive protein binding assay. In the acute state no difference in plasma 1,25(OH)2D3 level between sham-operated (SHAM) and unilateral-nephrectomized (UNI-NX) rats was found. The presence of the thyroparathyroid glands was not required for maintaining plasma 1,25(OH)2D3 at a normal level 48 hr after UNI-NX. In the chronic state in rats fed at 1.1% Ca diet, plasma 1,25(OH)2D3 (means +/- SEM) was 94 +/- 4 in SHAM and 98 +/- 8 pM in UNI-NX. In rats fed a 0.1% Ca diet it was 252 +/- 16 in SHAM and 239 +/- 20 pM in UNI-NX. Analysis of 3H-1,25(OH)2D3 plasma decay curve indicated that in UNI-NX under a high calcium diet the normalization of plasma 1,25(OH)2D3 appears to be entirely due to an increase in production, whereas under a low calcium diet part of it may also result from a moderate decrease in the elimination rate. In conclusion, this study indicates that unilateral nephrectomy does not affect the level of plasma 1,25(OH)2D3 even under a calcium restriction challenge. This compensatory adaptation appears to be independent of parathyroid hormone.
 ...
PMID:Unilateral nephrectomy and 1,25-dihydroxyvitamin D3. 668 42

Earlier studies have shown that an oral sodium (Na) load may induce hypercalciuria in previously normocalciuric subjects and may also increase intestinal calcium (Ca) absorption. To probe the cause of the increased intestinal Ca absorption, we simultaneously measured parathyroid function, serum 1,25-dihydroxyvitamin D [1,25-(OH)2D], and fractional intestinal 47Ca absorption before and after a salt load. Eleven normal subjects and two patients with postsurgical hypoparathyroidism were placed on a 10 meq Na, 400 mg Ca per day diet for 10 days, followed by another 10-day period in which the same diet was supplemented by 240 meq Na daily. Measurements were performed on the final 3 days of each phase. In the normal subjects, urinary Na excretion increased from 7 +/- 2 to 226 +/- 8 meq/day (mean +/- SEM), urinary Ca rose from 110 +/- 14 to 167 +/- 16 mg/day, serum parathyroid hormone (PTH) increased from 20 +/- 1 to 22 +/- 1 muleq/ml, serum 1,25-(OH)2D rose from 38 +/- 4 to 51 +/- 7 pg/ml, and fractional intestinal 47Ca absorption increased from 0.39 +/- 0.03 to 0.49 +/- 0.03 (P less than 0.05 for all changes). Serum Ca corrected for total protein did not change (9.9 +/- 0.1 to 9.8 +/- 0.1 mg/dl). The patients with hypoparathyroidism who were maintained on vitamin D therapy also showed increases in urinary Na (20 +/- 12 to 245 +/- 11 meq/day) and urinary Ca (271 +/- 48 to 305 +/- 43; P less than 0.05). However, there were no increases in serum PTH (13 +/- 1 to 11 +/- 1 muleq/ml), serum 1,25-(OH)2D (44 +/- 1 to 40 +/- 6 pg/ml), or intestinal Ca absorption (0.41 +/- 0.03 to 0.42 +/- 0.05). Corrected serum Ca decreased from 9.4 +/- 0.2 to 8.6 +/- 0.2 mg/dl. We conclude that in normal subjects, Na-induced renal hypercalciuria is accompanied by increased 1,25-(OH)2D synthesis and enhanced intestinal Ca absorption. Since this adaptive mechanism did not occur in two patients with hypoparathyroidism, mediation by PTH is suggested.
 ...
PMID:The role of dietary sodium on renal excretion and intestinal absorption of calcium and on vitamin D metabolism. 689 38

The effects of continuous ambulatory peritoneal dialysis on parathyroid hormone (PTH) and mineral metabolism were evaluated in ten patients. Utilizing a PTH radioimmunoassay, which measures both intact hormone and carboxyl-terminal PTH fragments, it was found that the mean clearance of immunoreactive parathyroid hormone was 1.5 +/- 0.73 ml/min (SEM) yielding a daily net removal of 13.6 +/- 3.2% of estimated total extracellular parathyroid hormone. Gel electrophoresis of the dialysate revealed the presence of both intact parathyroid hormone and fragments in a similar pattern to that of peripheral plasma. Normal levels of 25-(OH) vitamin D and vitamin D binding protein were observed prior to the initiation of continuous ambulatory peritoneal dialysis and following 6 months of treatment. Timed dialysate collections (N = 93) demonstrated a daily calcium influx of only 9.9 +/- 9.7 mg. The daily removal of phosphorus was 308.4 +/- 15.5 mg. Despite elevated serum magnesium levels in all patients, the net daily removal was inadequate (31.2 +/- 15.5 mg). It was concluded that: (1) Unlike chronic hemodialysis, continuous ambulatory peritoneal dialysis removes significant amounts of parathyroid hormone. (2) Normal 25-(OH) vitamin D and vitamin D binding protein levels are maintained with continuous ambulatory peritoneal dialysis despite large protein losses. (3) Substantial amounts of phosphorus are removed with continuous ambulatory peritoneal dialysis but not to an extent that precludes use of phosphorus binders. (4) Dialysate containing lower magnesium and possibly higher calcium concentrations should be made available to improve mineral homeostasis.
 ...
PMID:Minerals, vitamin D, and parathyroid hormone in continuous ambulatory peritoneal dialysis. 689 87

We studied the effects of glucocorticoid excess on calcium and phosphorus homeostasis in relation to vitamin D metabolites and parathyroid hormone (PTH) in seven patients with spontaneous ACTH-dependent Cushing's syndrome. Remission of hypercortisolism resulted in a significant increase in tubular reabsorption of phosphate [from 76 +/- 4% to 89 +/- 2% (mean +/- SEM); P less than 0.01] and serum phosphorus (from 3.1 +/- 0.1 to 4.2 +/- 0.2 mg/dl; P less than 0.005). Serum calcium did not change, although there was a reduction in daily urinary calcium excretion from 0.23 +/- 0.02 to 0.107 +/- 0.02 mg calcium/mg creatinine. Serum immunoreactive PTH (iPTH) levels were normal during Cushing's syndrome (34 +/- 5 microleq/ml), but fell significantly after remission to 22 +/- 2 microleq/ml (P less than 0.05). This small decrease in iPTH did not correlate with the improvement of phosphate homeostasis. Plasma 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D [1,25-(OH2)D] concentrations in Cushing's syndrome did not differ from measurements in 97 normal subjects. After treatment, 25OHD did not change, but 1,25-(OH)2D fell in each patient from a mean of 44 to 22 pg/ml (P less than 0.02). 1,25-(OH)2D was inversely correlated with serum phosphorus (r = 0.59; P less than 0.01), but did not correlate with iPTH. The known impairment of intestinal calcium absorption in Cushing's syndrome cannot be attributed to a decrease in the circulating levels of 1,25-(OH)2D. Endogenous hypercortisolism decreases tubular phosphate reabsorption and serum phosphorus, increase tubular phosphate reabsorption and serum phosphorus, increases iPTH, and results in an increase in 1,25-(OH)2D. These events may contribute to the severe loss of bone mass in such patients and may account for the calciuria and phosphaturia of Cushing's syndrome.
 ...
PMID:Vitamin D metabolites and parathyroid hormone in Cushing's syndrome: relationship to calcium and phosphorus homeostasis. 697 49

Rats were semistarved over a 7-week period, resulting in a loss of 28.2 +/- 1.6% (SEM) of their initial body weights, while ad libitum fed controls gained 15.1 +/- 1.8% (SEM). Bone loss occurred and skeletal turnover was markedly reduced in the semistarved rats, as evidenced by a paucity of osteoid and osteoclasts, failure of the bone to assume a tetracycline label, and reduced urinary hydroxyproline excretion. Despite these changes, there were no alterations of serum or bone alkaline phosphatase activity with semistarvation, and analysis of tibial mineral content revealed reductions only in magnesium and sodium. The malnourished animals, however, were hypercalciuric and hypophosphatemic. Semistarvation had no effect on circulating levels of immunoreactive parathyroid hormone or 25-hydroxyvitamin D, but did result in reduced serum levels of corticosterone, insulin, and 1,25-dihydroxyvitamin D. Therefore, it appears that the effects of semistarvation on the rat skeleton are osteoporotic rather than osteomalacic, and that the defect is the consequence of reduced bone turnover. The contribution which the abnormalities of bone-regulating hormones play in the genesis of this skeletal lesion remains to be determined.
 ...
PMID:Effects of semistarvation on skeletal homeostasis. 700 Apr 97

Dispersed parathyroid cells were employed to study calcium-regulated parathyroid hormone (PTH) release in severe secondary hyperparathyroidism due to chronic renal insufficiency. Cell preparations were obtained from 16 parathyroid glands of 6 patients undergoing subtotal parathyroidectomy for parathyroid bone disease and/or hypercalcemia. The effects of increasing ambient calcium concentration on immunoreactive PTH release in vitro were assessed and compared with results observed in cells prepared from 7 adenomas and 6 normal parathyroid glands. There was no difference in maximal PTH release for the 3 types of tissue (mean +/- SEM, 8.48 +/- 1.9 , 8.1 +/- 3, and 10.1 +/- 0.78 ng/10(5) cells. h respectively). In 14 of 16 hyperplastic glands, 6 of 7 adenomas, and all of the normal glands, PTH release was inhibited more than 50% by 2-3 mM calcium (suppressible glands). Of the normal glands, half of the maximal inhibition of PTH release (the set-point) occurred at less than 1.03 mM calcium in 5 of 6 cases. In 12 of 14 suppressible hyperplastic glands and all of the 6 suppressible adenomas, on the other hand, the set-point was 1.03 mM or higher (p less than 0.01 and P less than 0.002, respectively). Thus, in severe secondary parathyroid hyperplasia due to chronic renal insufficiency, there is frequently an increase in the set-point for calcium without a change in the maximal secretory rate per cell. Abnormal calcium-regulated PTH release at the cellular level, therefore, is not limited to parathyroid neoplasia (i.e. adenoma or primary hyperplasia), but may occur in secondary hyperplasia as well.
 ...
PMID:Abnormal regulation of parathyroid hormone release by calcium in secondary hyperparathyroidism due to chronic renal failure. 705 14

In man as well as in experimental animals progressive renal failure is associated with a decrease in the fractional reabsorption (FR) of inorganic phosphate (Pi). This response has been considered as an adaptation phenomenon and generally attributed to an increase in parathyroid hormone (PTH) secretion. One report indicates that in chronic thyroparathyroidectomized (TPTX) dogs treated with large doses of vitamin D progressive renal failure can also be associated with a fall in FRPi. However, in this latter study the concomittant administration of vitamin D could have accounted for the observed decrease in FRPi. In our study we investigated whether or not chronic reduction in renal mass leads to a similar decrease in maximal net tubular Pi reabsorption per volume of glomerular filtrate (maximal TRPi/ml GF) in the presence and absence of PTH and without pharmacological supplementation in vitamin D. Male rats were either TPTX or sham-operated (intact). One and two weeks later the animals of both groups were either subtotally nephrectomized (NX) in two stages or sham-operated (control). Four weeks after the second renal operation, the glomerular filtration rate (GFR) and the reabsorption of Pi were determined by clearance methodology under acute sodium chloride and Pi infusion, that is, at endogenous and increased plasma Pi concentrations ([Pi]Pl.). Thus maximal TRPi/ml GFR could be determined. In rats with intact parathyroid glands GFR was 1.56 +/- 0.10 (mean +/- SEM) and 0.54 +/- 0.10 ml/min in control and NX respectively, whereas maximal TRPi/ml GF was 2.24 +/- 0.07 in control and 1.57 +/- 0.18 mumol/ml (P less than 0.005) in NX. In TPTX rats GFR was 1.66 +/- 0.27 and 0.62 +/- 0.06 ml/min in control and NX respectively, whereas maximal TRPi/ml GF was 3.80 +/- 0.20 in control and 2.95 +/- 0.13 mumol/ml (P less than 0.005) in NX. The marked decrease in maximal TRPi/ml GF observed in TPTX after subtotal NX could not be ascribed to any consistent change in plasma calcium. Our study provides conclusive evidence that the decrease in maximal TRPi/ml GF in response to renal mass reduction can occur to the same degree in the presence or absence of PTH.
 ...
PMID:Parathyroid hormone-independent adaptation of the renal handling of phosphate in response to renal mass reduction. 708 83

The pathogenetic roles of idiopathic renal hypercalciuria and absorptive hypercalciuria in children with urolithiasis have not yet been determined. Oral calcium loading studies were performed in 21 children with unexplained calcareous urolithiasis. Thirteen children, aged 20 months to 17 years, were found to have renal hypercalciuria after an overnight fast (urinary calcium-urinary creatinine [UCa/UCr] ratio in milligrams, greater than 0.21). Four children were found to have absorptive hypercalciuria. In this group, fasting UCa/UCr values were normal (SEM, 0.12 +/- 0.02); however, UCa/UCr values were elevated (SEM, 0.31 +/- 0.01) after the oral calcium load. Serum parathyroid hormone values were normal in all children with hypercalciuria. Urinary calcium excretion was normal in four patients. These data indicate that hypercalciuria may frequently occur in children with urolithiasis and that detailed metabolic evaluation is warranted in children with kidney stone disease.
 ...
PMID:Hypercalciuria in children with urolithiasis. 710 17


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