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Biomedical subjects

S B Oldham

Publications and source records attributed to S B Oldham.

At least 37 records · Page 2Linked to original sources
PubMed1978

Parathyroid hormone secretion in magnesium deficiency.

The effect of an acute elevation of the serum magnesium concentration on the concentrations of serum immunoreactive parathyroid hormone (IPTH) were studied in hypocalcemic hypomagnesemic patients, hyperparathyroid patients, and normal individuals. Basal serum IPTH concentrations in the hypomagnesemic patients ranged from undetectable to 3 times the upper limit of normal. All hypomagnesemic patients were observed to have an immediate rise in the serum IPTH concentration after magnesium administration regardless of the basal IPTH concentration. In contrast, normal individuals and patients with primary and secondary hyperparathyroidism responded to magnesium administration with either a decrease or little change in the serum IPTH concentration. These date indicate that an acute stimulation of PTH secretion induced by magnesium is characteristic of the magnesium-deficient state. The consistency of this response suggests that impaired PTH secretion is a significant factor contributing to the hypocalcemia of magnesium deficiency.

Calcium↗
PubMed1977

Effectiveness of 1 alpha-hydroxyvitamin D3 in children with renal osteodystrophy associated with hemodialysis.

Two children who were receiving maintenance hemodialysis were treated with 1 to 4 microng/day of 1 alpha-hydroxyvitamin D3 for 500 to 700 days, respectively. Sequential parathyroid hormone levels and radiologic evaluations showed considerable improvement in one patient. The second patient initially responded with healing of the bone disease. Subsequent deterioration may be related either to medical noncomplicance and/or interference by diphenylhydantoin in the subsequent hepatic 25-hydroxylation of 1 alpha-OH-D3.

Adolescent↗
PubMed1977

Urinary cyclic AMP analyzed as a function of the serum calcium and parathyroid hormone in the idfferential diagnosis of hypercalcemia.

Urinary cyclic AMP (UcAMP) appropriate for the serum calcium concentration was determined in normal subjects during the base-line state and during alteration in their serum calcium concentrations by saline and calcium infusions. This was compared to the UcAMP in 76 patients with hypercalcemia and 5 patients with hypocalcemia. In 54 of 56 patients with primary hyperparathyroidism, the UcAMP was inappropriately high for their serum calcium concentration, the 2 exceptions having renal failure. In four patients with vitamin D intoxication, sarcoidosis, milkalkali syndrome, and thiazide-induced hypercalcemia and in five patients with hypocalcemia due to hypoparathyroidism, the UcAMP was appropriately low for their serum calcium concentration. In 16 patients with nonparathyroid neoplasms, 10 had UcAMP levels that were inappropriately high suggesting ectopic parathyroid hormone (PTH)-mediated hypercalcemia and 6 had UcAMP levels that were appropriately low suggesting that their hypercalcemia was due to osteolytic factors other than PTH. Correlations between UcAMP, serum calcium concentration, and carboxyl-terminal immunoreactive PTH suggest that random UcAMP is a sensitive accurate reflection of circulating biologically active PTH. If there is adequate renal function (serum creatinine concentration less than 2.0 mg/dl), a random UcAMP expressed as mumol/g creatinine and analyzed as a function of the serum calcium concentration completely separates patients with PTH and non-PTH-mediated hypercalcemia.

Adult↗
PubMed1976

Functional hypoparathyroidism and parathyroid hormone end-organ resistance in human magnesium deficiency.

Hypocalcaemia is a well-recognized manifestation of magnesium deficiency. We have studied seventeen patients with this syndrome in an attempt to determine the pathogenesis of the hypocalcaemia. Mean initial serum calcium concentration was 5-6 mg/dl and mean initial serum magnesium concentration was 0-75 mg/dl. Serum immunoreactive parathyroid hormone (IPTH) was measured in sixteen patients in the untreated state. Despite severe hypocalcaemia, serum IPTH was either undetectable (less than 150 pg/ml) or normal (less than 550 pg/ml) in all but two patients. Serial measurements made during the initial 4 days of magnesium therapy in four patients showed an increase in serum IPTH within 24h, but a delayed increase in serum calcium, which required approximately 4 days to reach normal values. The effect of the rapid normalization of serum magnesium on serum IPTH and serum calcium concentration was studied in three patients. Within 1 min after 144-300 mg of elemental magnesium was administered i.v., serum IPTH had risen from undetectable to 3600 pg/ml and 1725 pg/ml in two patients and from 425 pg/ml to 937 pg/ml in the third. Serum calcium concentrations were unchanged after 30-60 min. These data provide evidence for impaired parathyroid gland function in most of the magnesium deficient patients. The rapidity with which serum IPTH rose in response to magnesium therapy indicates that this may reflect a defect in parathyroid hormone (PTH) secretion rather than its biosynthesis. The failure of serum calcium concentration to increase during the initial days of magnesium repletion, at a time when serum IPTH concentrations were normal or elevated, suggests end-organ resistance to PTH in these patients. The renal response to PTH was examined in two magnesium deficient patients by measurement of urinary cyclic AMP excretion following administration of parathyroid extract. In both patients there was a minimal increase in urinary cyclic AMP concentrations. In contrast, when the hepatic response to glucagon was tested on the same patients by measurement of plasma cyclic AMP concentrations following administration of glucagon, normal increases were observed. These results suggest that adenylate cyclase systems of various organs may be affected differentially by a state of magnesium deficiency. It is suggested that magnesium deficiency may result in defective cyclic AMP generation in the parathyroid glands and in the PTH target organs. This could be the principal mechanism operative in both impaired PTH secretion and end-organ resistance to PTH which together contribute to the development of hypocalcaemia.

Adult↗
PubMed1976

Vitamin D: the discovery of its metabolites and their therapeutic applications.

Our understanding of the role of vitamin D in calcium-phosphorus metabolism has changed considerably in the last decade. Studies performed in tissue culture, animal, and man have firmly established that the natural compound requires hydroxylation in the liver at the C-25 position and in the kidney at the C-1 position to form the biologically active derivative 1,25-(OH)2D3. These hydroxylation reactions are finely regulated to maintain normal calcium-phosphorus homeostasis: We now regard 1,25-(OH)2D3 as a hormone which is released by the kidney during periods of hypocalcemia. This hormone acts on the intestinal mucosa to facilitate calcium absorption and on bone to increase calcium mobilization. Its function in other tissues is still being evaluated. The active metabolites of vitamin D and several closely related analogs have been synthesized. It has been clearly demonstrated that 1,25-(OH)2D3 and 1alpha-OH-D3 promote healing in uremic bone disease. Administration of small amounts of these compounds has corrected the biochemical disturbances in vitamin D-dependency and hypoparathyroidism. Limited clinical experience with 25-OH-D3 and 1,25-(OH)2D3 in children with familial hypophosphatemia has failed to show convincing evidence of a therapeutic effect. Further clinical studies are needed to fully evaluate the therapeutic potential of this new family of compounds.

Animals↗
PubMed1975

1-alpha-hydroxyvitamin D3 in chronic renal failure. A potent analogue of the kidney hormone, 1,25-dihydroxycholecalciferol.

In chronic renal disease, the synthesis of the kidney hormone, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), is impaired, thus contributing to the development of renal osteodystrophy. The clinical use of 1,25-(OH)2D3 is limited, due to the complexity and expense of its chemical synthesis. This study reports the use of 1-alpha-hydroxyvitamin D3 (1-alpha-OH-D3), an active analogue of 1,25-(OH)2D3, in eight patients with chronic renal failure, five of whom were undergoing long-term hemodialysis. The drug was given orally for 6 to 260 days at a dosage of 1mug to 4mug/day. Short-term (21 days) balance studies showed an increase in intestinal calcium absorption and a simultaneous fall in serum parathyroid hormone levels during administration of 1-alpha-OH-D3. In two long-term studies (160 and 260 days), roentgenographic improvement of renal osteodystrophy was seen after 45 and 185 days, respectively. The data indicate that 1-alpha-OH-D3 holds considerable promise for the prevention and treatment of renal osteodystrophy.

Administration, Oral↗
PubMed1972

Calcium-regulated parathyroid hormone peptidase.

An enzymatic activity that catalyzes the conversion of glandular parathyroid hormone to a smaller-molecular-weight, biologically and immunologically active form of this hormone has been extracted from normal parathyroid and other porcine tissues. The product of the conversion has the immunologic characteristics of the hormone that occurs in peripheral serum and in tissue culture medium from parathyroid explants. The enzyme is activated by chelating agents and is inhibited by high calcium concentrations, suggesting that this enzyme may be important in the regulation of secretion or metabolism of the hormone.

Animals↗
PubMed1970

Native human parathyroid hormone: an immunochemical investigation.

We have produced an antiserum to porcine parathyroid hormone (PTH) which distinguishes between the PTH in human hyperparathyroid serum and that in extracts of parathyroid adenomata. The PTH secreted into the medium by parathyroid adenoma slices in culture reacts with this antiserum in the same way as the PTH in human hyperparathyroid serum, but extraction of the same serum by a conventional procedure used for the extraction of glandular tissue converts the serum hormone to a species which reacts more like hormone extracted from adenomata. The results suggest that we have immunologically identified a native molecular species of PTH, that the antiserum used recognizes primarily this species in human hyperparathyroid serum, and that the PTH extracted from parathyroid adenomata is immuno-chemically altered.

Adenoma↗