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Biomedical subjects

M Peacock

Publications and source records attributed to M Peacock.

At least 145 records · Page 8Linked to original sources
PubMed1981

The vitamin D metabolites in the pathogenesis and management of osteoporosis.

Studies on post-menopausal osteoporotic patients indicate that 1,25-(OH)2 D3 concentrations are no different from those in age-matched normal subjects and the data suggest that the malabsorption of calcium found in many osteoporotic patients cannot generally be attributed to low plasma 1,25-(OH)2 D3 levels. The effects are discussed of three different therapies - sex hormones alone, vitamin D metabolites alone and a combination of both - on calcium balance and peripheral bone loss in treated compared with untreated osteoporotic patients. The results indicate that combined therapy with a vitamin D metabolite and an oestrogen is more effective in inhibiting the rate of bone resorption in post-menopausal osteoporosis than treatment with either agent used alone, and should be regarded as the treatment of choice at the present time. It is suggested that, using this regimen which is suitable for patients up to about 65 years of age, calcium supplementation is not required, provided daily calcium intake is reasonably adequate, and may even be undesirable by increasing the risk of hypercalcaemia.

Calcitriol↗
PubMed1981

Biochemical evidence of vitamin D deficiency in pregnant Asian women.

Levels of plasma 25-hydroxy-vitamin D (25 OHD) were found to be lower in 58 pregnant Asians when compared with 59 Caucasian controls. Thirty per cent of Asians and none of the controls had levels less that 10 ng/ml. The low plasma was associated with biochemical evidence of secondary hyperparathyroidism and increased bone turnover as assessed by plasma parathyroid hormone, alkaline phosphatase and urinary hydroxyproline. Vitamin A and its binding protein, and vitamin D binding protein, were also measured in a subgroup of 40 patients. There was no difference between Asians and their controls. The data suggest that vitamin D supplementation would be beneficial in Asian women during pregnancy.

Asia↗
PubMed1980

Purification of plasma vitamin D metabolites for radioimmunoassay.

The ability of four solvent systems to extract tritiated 25-hydroxy vitamin D3, 24,25-dihydroxy vitamin D3, 25,26-dihydroxy vitamin D3 and 1 alpha, 25-dihydroxy vitamin D3 from plasma was compared. Diethyl ether gave the highest yield of metabolites and lowest yield of "lipid" materials, the dihydroxylated metabolites were more readily extracted than 25-hydroxy vitamin D3. Following extraction with ether the vitamin D metabolites could be separated, without prior purification, on a 6.2 mm X 250 mm Zorbax-Sil high pressure liquid chromatography (HPLC) column, a simplification of previous methods. Plasma 1 alpha, 25-dihydroxy vitamin D levels measured after purification by this method were not significantly different from those obtained by an established, more complex method.

24,25-Dihydroxyvitamin D 3↗
PubMed1980

Plasma 1,25(OH)2 vitamin D measured by radioimmunoassay and cytosol radioreceptor assay in normal subjects and patients with primary hyperparathyroidism and renal failure.

Antibodies to 1 alpha, 25-dihydroxy vitamin D3 25-hemisuccinate linked to albumin were produced and an immunoassay for 1,25-dihydroxy vitamin D developed. Plasma 1,25-dihydroxy vitamin D concentrations were compared using an immunoassay and cytosol radioreceptor assay. Both assays gave comparable results but the immunoassay was more reproducible, slightly more sensitive and had a lower detection limit. Using the immunoassay the plasma 1,25-dihydroxy vitamin D was 110.5 pmol/l (S.D. 29.4) in normal subjects; there was no difference between males and premenopausal females. It was negatively related to plasma phosphate. In renal failure and primary hyperparathyroidism plasma 1,25(OH)2D was positively related to radiocalcium absorption. Following 1 and 2 microgram of 1,25-dihydroxy vitamin D3 given orally the peak plasma concentration occurs within 12 h.

Adult↗
PubMed1980

The decline in vitamin D status with age.

A cross-sectional study of plasma 25-hydroxy-vitamin D (250HD) concentrations in healthy women in the age range 20-96 years is reported. Mean values decline with increasing age while abnormally low levels of plasma 250HD are more common in the elderly. The decline in vitamin D status with age is probably the result of lack of sunlight exposure associated with social factors and physical immobility.

25-Hydroxyvitamin D 2↗
PubMed1980

The cause of idiopathic calcium stone disease: hypercalciuria or hyperoxaluria?

Hypercalciuria is common in patients who form calcium oxalate urinary stones and is considered by many to be the cause of the disorder. This review shows that there is little relationship between either the rate of stone-formation or calcium oxalate crystalluria and the urinary excretion of calcium. There is, however, a strong relationship between these parameters and the urinary excretion of oxalate which is slightly, but significantly, elevated in stone-formers compared with normals. It is concluded that this mind degree of hyperoxaluria may be much more important than hypercalciuria in the genesis of calcium oxalate stones.

Calcium↗
PubMed1980

Factors influencing the intestinal absorption of calcium and phosphorus following renal transplantation.

After successful renal transplantation there is continuing malabsorption of calcium and phosphorus. This is due in part to impaired glomerular filtration rate, and in part to the action of steroid on calcium and phosphorus absorption. The effect of steroids is most marked over the first 18 months after transplantation and causes significant malabsorption of calcium and phosphorus even though good graft function is established. Calcium and phosphorus malabsorption can be improved by exogenous 1,25-dihydroxy vitamin D (oral 1 alpha-OH D3 or 1,25-[OH]2D3).

Adolescent↗
PubMed1980

Clinical and metabolic aspects of urinary stone disease in Leeds.

In summary, the persistent passage of urine excessively supersaturated with calcium oxalate and/or calcium phosphate in conjunction with a low level of inhibitory activity increases the risk of abnormal crystalluria and stones in a given individual. Treatment of the disorder must be aimed at correcting the abnormal risk factor(s) in that individual.

Adolescent↗
PubMed1979

Plasma 25-hydroxyvitamin D in pregnant Asian women and their babies.

Plasma 25-hydroxyvitamin D (25-OHD) was measured in cord blood taken at delivery and in fasting blood taken from 44 Asian mothers in the first day of the puerperium. Blood was taken from the baby 48 h after delivery. Cord-blood samples were also taken at 43 non-Asian deliveries. Plasma 25-OHD concentrations in Asians were low at delivery; in 81% of the mothers and 36% of the babies plasma 25-OHD was in the osteomalacic range. Asian lower than concentrations in non-Asian controls. 4 Asian babies had vraniotabes and 1 had neonatal tetany. 1 non-Asian baby had craniotabes. A review of 3327 deliveries in 1978 confirmed that neonatal tetany was significantly more common in Asian babies (2.3%) than in non-Asian babies (0.3%). In 44 other Asian mothers supplements of 1000 units of vitamin D daily during pregnancy significantly increased plasma-25-OHD concentrations at delivery.

Asia↗