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Biomedical subjects

J A Raymakers

Publications and source records attributed to J A Raymakers.

At least 37 records · Page 2Linked to original sources
PubMed1990

[Hypercalcemia in the elderly].

The symptoms which are caused by hypercalcemia are variable and unspecific. In the elderly the functional capacity of homeostatic mechanisms is less than in young people and at the same time the prevalence of diseases which may cause hypercalcemia is greater. One should be aware of the possibility of hypercalcemia in patients presenting vague gastrointestinal and/or psychiatric complaints or symptoms. The prevalence of hypercalcemia in elderly women may well be 3%. Hypercalcemia leads to renal loss of salt and disturbances of renal function. An increasing inability to excrete the calcium overload is the result. Only in primary hyperparathyroidism renal function remains generally normal and moderately increased calcium levels may exist for years without serious consequences. Important causes of hypercalcemia in the elderly are hyperthyroidism, malignant disease and abrupt immobilization with previously elevated skeletal remodelling activity. Thiazide diuretics may precipitate the hypercalcemic state. Diagnosis is relatively simple and is based on a limited package of laboratory tests. Treatment should always begin with the restoration of the extracellular fluid volume. This is followed by inhibition of bone resorption by means of bisphosphonates or corticosteroids and treatment of the underlying disease.

Aged↗
PubMed1989

No short-term effects of 24,25-dihydroxycholecalciferol in healthy subjects.

Seven healthy volunteers were given 25 micrograms of 24,25-DHCC for one week to study the effects on calcium and bone metabolism. Mean plasma 24,25-DHCC concentration increased from 2.2 +/- 1.7 micrograms/l to 10.8 +/- 6.1 micrograms/l (p less than 0.001). No significant change was seen in the fasting plasma concentrations of Ca, Ca++, PTH and alkaline phosphatase activity and in urinary excretion of calcium and hydroxyproline and in tubular reabsorption of phosphate. The area under the curve for plasma ionized calcium concentration and urinary excretion of calcium during a standard calcium infusion of 10 mg/kg of Ca in 2 h did not change by 24,25-DHCC. We conclude that in healthy subjects no effect of 24,25-DHCC on the steady state parameters of calcium and bone metabolism, on renal calcium handling and on the handling of an intravenous calcium challenge by the homeostatic system could be demonstrated.

24,25-Dihydroxyvitamin D 3↗
PubMed1988

Bone mineral content of the forearm in healthy Dutch women.

Single energy photon absorptiometry is a reliable technique for assessing the bone mineral content (BMC) of cortical bone in the forearm. It can also be used for BMC measurement in the ultradistal part of the forearm, where there is a considerable proportion of trabecular bone. The results of a BMC survey at both sites in healthy Dutch women, aged 26-75 yr, are reported, and the differences and changes with age are discussed. The technique offers possibilities for a rational screening programme in post-menopausal women, because of its high precision, low radiation dose, speed and low cost. The validity of the ultradistal measurement for the detection of abnormally fast bone mineral loss from trabecular bone in the individual patient has yet to be proven.

Adult↗
PubMed1988

Acute changes in calcium and bone metabolism during methylprednisolone pulse therapy in rheumatoid arthritis.

Corticosteroids (CS) decrease bone formation and enhance bone resorption and this can lead to osteopenia. Bone metabolism was studied during the administration of huge amounts of CS (1000 mg methylprednisolone) over a short period of time in 10 patients with persistently active rheumatoid arthritis. The effects could be divided into those occurring within 24 h: (a) a decrease in bone resorption (urinary excretion of calcium and hydroxyproline) and bone formation (alkaline phosphatase); (b) a decrease in renal excretion of calcium; (c) an increase in concentration of serum 1,25-dihydroxy-cholecalciferol and those secondary effects arising after 24 h; (d) a decrease in serum calcium due to the decrease in intestinal Ca absorption and the decrease in renal tubular reabsorption of Ca; (e) an increase in serum PTH concentrations. In a previous study it was found that these changes normalized within a few days after completion of the CS treatment.

Adult↗
PubMed1987

Responders and non-responders after fluoride therapy in osteoporosis.

Patients with osteoporosis were treated for two years with sodium fluoride. Fifteen received sodium fluoride in capsules, 56 in enteric coated slow release tablets (Ossin) and 20 in enteric coated tablets (Procal). Seven women treated with Procal were also treated with oestrogens. All patients had a calcium intake between 1000 and 2000 mg/day, used dihydrotachysterol for vitamin suppletion and were advised to exercise. Non-responders were arbitrarily defined as those who had an increase in serum alkaline phosphatase less than 10 U/l, those who had no increase in bone mineral content measured with CT in L4 and those who got a femoral neck fracture during the period of therapy. In the overall group of 91 patients 20% were non-responders based on a serum alkaline phosphatase increase less than 10 U/l. Based on the changes in bone mineral content 40% were non-responders during the first year of treatment, 45% during the second year and 23% over the first plus second year. The impression is that patients with a femoral neck fracture have a higher increase in serum parathyroid hormone concentration than patients without fractures. The urinary excretion of fluoride has a better predictive value than the change in serum alkaline phosphatase concentration for the prediction of an increase in bone mineral content.

Aged↗
PubMed1987

Monitoring fluoride therapy in osteoporosis by dual photon absorptiometry.

Dual photon absorptiometry (DPA) was used to evaluate changes in bone mineral mass in 108 osteopenic patients. Ninety were treated with fluoride and 18 served as controls. All osteopenic patients and 9 of the controls took calcium and vitamin D supplements. In 16 women estrogens were combined with the fluoride therapy. Seven patients received prednisone. Significant positive changes in bone mineral mass in the lumbar spine could be demonstrated over a mean observation time of 14-15 months in all groups treated with fluoride but not in the control group. The average increase in bone mineral mass in the lumbar spine (L2, L3 and L4 combined) ranged from 3.57% +/- 1.42% (sem, p less than 0.05) in women on fluoride to 10.36% +/- 3.17% (p less than 0.01) in men and 10.18% +/- 2.39% (p less than 0.001) in women on estrogen and fluoride. Changes in bone mineral mass in femoral necks (left and right combined) and femoral diaphysis were not significant. In the control group no significant changes were observed (lumbar spine: -1.68% +/- 1.75%, femoral necks -0.09% +/- 3.3% and femoral diaphysis -2.32% +/- 2.40%). It is concluded that a positive effect of fluoride on trabecular bone in the spine can be demonstrated with DPA on a group basis when data processing is done in a uniform way by a single observer. Its longitudinal use in individual patients necessitates a series of measurements to overcome the analytical error.

Adult↗
PubMed1986

Fracture prevalence and bone mineral mass in osteoporosis measured with computed tomography and dual energy photon absorptiometry.

In 174 adults presenting with backache, bone densitometry was performed on the lumbar spine, both femoral necks, and one femoral shaft employing dual energy photon absorptiometry (DPA); in 112 of these, densitometry was undertaken on L4 using single energy quantitative computer assisted tomography (CT). Radiographs of the spine were obtained in all patients and those with known or suspected malignant disease were excluded. The subjects were divided into two groups according to the presence (n = 128) or absence (n = 44) of signs of vertebral collapse or compression. The predictive value of the densitometric results for the presence of vertebral fractures was calculated and used as an estimate of fracture risk. While CT showed somewhat higher predictive values than DPA of the spine or combinations of DPA results from spine and femoral necks, the difference was not significant. It is concluded that with both CT and DPA the probability of the presence or absence of fracture can be raised to 75-80% when the probability prior to the investigation is 50% and when the threshold values of the measurements are chosen so that their sensitivity and specificity are about equal.

Adult↗
PubMed1985

Treatment of renal osteodystrophy in children with dihydrotachysterol and 24,25-dihydroxyvitamin D3.

The effect of administration of 25 micrograms 24,25-dihydroxyvitamin D3 (24,25(OH)2D) combined with dihydrotachysterol (DHT2) on clinical, radiological, biochemical and bone histological parameters was assessed in ten children on chronic hemodialysis. Eight children had been treated with DHT2 prior to administration of 24,25(OH)2D. Addition of 24,25(OH)2D to the treatment resulted in a decrease in serum calcium values. Therefore higher doses of DHT2 were required to maintain serum-calcium levels between 2.4-2.8 mmol/l. Administration of 24,25(OH)2D did not modify the quality of bone, but histomorphometric investigation did show a significant reduction of the surface percentage of bone trabecula, in the iliac crest, covered with osteoclasts (oc%). Following the administration of 24,25(OH)2D an increase in bone mineralization was shown by X-rays of the wrists and measured by dual photonabsorptiometry. Addition of 24,25(OH)2D to the DHT2 treatment resulted in an increase in serum concentration of 24,25(OH)2D and a decrease in DHT2 levels. The present study suggests that administered 24,25(OH)2D interferes with DHT2 metabolism and increases DHT2 tolerance. Increased bone mineralization may be related to 24,25(OH)2D, a higher dose of DHT2 or both.

24,25-Dihydroxyvitamin D 3↗
PubMed1976

Calculation of three hours calcium absorption from a double isotope test; a simplified method.

For the rapid evaluation of calcium absorption in human subjects several isotopic tests have been proposed. Among them, the double isotope test based on the concurrent oral and intravenous administration of calcium isotopes seems the most reliable. However, the computations involved in this test, a deconvolution of the two specific-activity functions obtained, are quite extensive. By simulating these functions we developed a simple formula to calculate the absorption in the first three hours of the test. Applied to the data of 79 patients the result differed less than the experimental error from the absorption computed with the more elaborate deconvolution method.

Calcium↗
PubMed1975

Pre-operative localization of parathyroid adenomas or parathyroid hyperplasia by means of venous sampling.

Pre-operative localization of parathyroid tumours on primary hyperparathyroidism is discussed. 20 patients were examined in this way. Of the 15 patients who were operated on, the pre-operative findings of 12 correspond with the results of operations and histological examinations. These results correspond with what is known from other publications. Preoperative localization by means of venous sampling is possible in a large number of cases. The examination is especially important in patients with previous neck exploration.

Adenoma↗