Oral Calcium-loading Test in Rickets and in Neonatal Tetany: Effect of Vitamin D

In an oral calcium-loading test performed on 10 infants with vitamin-D deficiency rickets and low fasting calcium levels, a comparison of results before and after therapy showed that vitamin D raised the serum calcium level at each stage of the test and altered the response so that a more rapid and substantial rise and fall in serum calcium occurred.The effects of vitamin D therapy on newborn infants with hypocalcaemic hyperphosphataemic tetany in another study suggests that these infants should be treated in this way to make them more responsive to oral calcium therapy.     

Serum ionised calcium concentration: measurement versus calculation.

Four hundred and eighteen measurements of serum ionised calcium, total calcium, and protein concentrations were made from 47 normal volunteers, 104 patients with chronic renal failure (33 being treated conservatively and 71 with regular haemodialysis), and 83 renal transplant recipients. The serum ionised calcium concentration was measured with an Orion SS-20 meter and calculated from the total serum calcium and protein concentrations by using three formulae and a nomogram. In the normal subjects and patients undergoing regular haemodialysis, whose serum calcium concentrations were in or near the normal range, three of the calculations gave results similar to those obtained by direct measurement. In patients with conservatively treated chronic renal failure and those who had received renal transplants, however, there was poor aggrement between the methods. When patients with hypercalcaemia and hypocalcaemia from all the groups were considered separately there was again poor agreement between calculated and measured concentrations of serum ionised calcium. Of the patients whose measured concentrations of serum ionised calcium were high, 69-76% were classified as normal by the four indirect methods. We conclude that calculation of the serum ionised calcium concentrations is not an adequate substitute for direct measurement.     

Clinical Problems: Hypercalcaemia in Patients with Advanced Mammary Cancer

Hypercalcaemia and hypercalciuria are common complications of advanced mammary cancer. Of 127 patients with the disease 63 (49·5%) had some abnormality of calcium balance. Eighteen (14%) of these patients developed severe progressive hypercalcaemia and became acutely ill.Most patients had skeletal metastases, and the usual cause of hypercalcaemia was rapid destruction of bone by the cancer. One patient with severe uncontrollable hypercalcaemia and minimal skeletal involvement probably developed the complication due to inappropriate secretion of a parathyroid-hormone-like substance by massive hepatic deposits.Severe hypercalcaemia was controlled successfully in 13 of the 18 patients, the serum calcium levels returning to normal and the acute symptoms disappearing. Unfortunately, successful correction of the hypercalcaemia rarely was followed by prolonged survival from the underlying malignant disease. The incidence of subsequent objective response to pituitary ablation was less than usual, and only three patients survived for more than one year after the episode of hypercalcaemia.     

Calcium Metabolism in Acromegaly

A total of 78 acromegalic patients were studied before and after treatment by yttrium-90 needle implantation.Among the untreated patients 16% had a borderline or raised serum calcium. In half of these patients the serum calcium fell to normal after remission of their acromegaly. In the others the hypercalcaemia was due to associated proved or probable hyperparathyroidism. A downward trend of the serum calcium was noted even in the normocalcaemic patients with remission of their disease.Only 20% of untreated patients had a raised serum phosphate, and follow-up showed this measurement to be a poor index of disease activity.Net calcium absorption and calcium balances in five patients in this series and 12 others from the literature were essentially normal for their given level of calcium intake. No patient showed definite radiological evidence of osteoporosis and vertebral fractures.Bone uptake rate of calcium-47 and stable strontium was raised in the untreated state in all nine patients studied. The 24-hour strontium space was raised in 73% of untreated patients and fell to normal after treatment in all the retested patients in whom it was high initially.     

Paraneoplastic hypercalcaemia in ovarian carcinoma.

Five patients were seen in whom a raised serum calcium concentration was associated with ovarian carcinoma (clear cell in two cases, cystadenocarcinoma in three). None showed evidence of metastases in bone. The hypercalcaemia occurred as a paraneoplastic phenomenon, but biochemical studies suggested the production of a parathyroid-hormone-like substance. One patient remained free of symptoms of her hypercalcaemia throughout. Paraneoplastic hypercalcaemia due to ovarian carcinoma may be more common than generally recognised and present as a life threatening condition requiring urgent treatment.     

Single dose versus daily intravenous aminohydroxypropylidene biphosphonate (APD) for the hypercalcaemia of malignancy

Thirty patients with hypercalcaemia and known malignant disease were randomly allocated to receive 60 mg 3-amino-1-hydroxypropylidene-1, 1-bisphosphonate (APD) intravenously as a single dose or as consecutive daily doses of 30 mg (two days) or 15 mg (four days). The rate of infusion was the same for each regimen (7.5 mg/hour). Calcium concentrations fell in all patients and returned to normal in all but two. Relapse of hypercalcaemia occurred after a mean of 21 days in each group. Urinary calcium excretion fell in all groups and symptoms were greatly improved. After relapse patients were retreated with APD (30 mg as a single infusion) and normocalcaemia maintained by regular infusions at two to three week intervals.APD given as a single 60 mg infusion over eight hours together with rehydration is recommended as the initial management of the hypercalcaemia of malignancy, followed by 30 mg APD roughly every two to three weeks to maintain normal or near normal serum calcium concentrations.     

Effects of short-term recovery periods on fluid-induced signaling in osteoblastic cells

It is well known that cyclic mechanical loading can produce an anabolic response in bone. In vivo studies have shown that the insertion of short-term recovery periods (10-15 s) into mechanical loading profiles led to an increased osteogenic response compared to continuous cyclic loading of bone. Although this is suggestive of temporal processing at the bone cell level, there is little evidence to support such a hypothesis. Therefore, the current study investigated the cellular mechanism of bone's response to rest inserted vs. continuous mechanical loading. Cell responses to rest inserted mechanical loading were quantified by applying oscillatory fluid flow (OFF) to osteoblastic cells and quantifying real-time intracellular calcium [Ca2+]i, prostaglandin E2 (PGE2) release, and osteopontin (OPN) mRNA levels. Cells were exposed to OFF (1 Hz) at shear stresses of 1 and 2 Pa with rest periods of 5, 10, and 15s inserted every 10 loading cycles. The insertion of 10 and 15s rest periods into the flow profile resulted in multiple [Ca2+]i responses by individual cells, increased [Ca2+]i response magnitudes, and increased overall percent of cells responding compared to continuously loaded control groups. We determined the source of the multiple calcium responses to be from intracellular stores. In addition, rest inserted OFF led to similar levels of PGE2 release and increased levels of relative OPN mRNA compared to cells exposed to continuous OFF. Our study suggests that the cellular mechanism of bone adaptation to rest inserted mechanical loading may involve modulation of intracellular levels of calcium (frequency, magnitude, percent of cells responding).     

Effect of single high dose infusions of aminohydroxypropylidene diphosphonate on hypercalcaemia caused by cancer.

Single intravenous infusions of 30 mg aminohydroxypropylidene diphosphonate were given to 16 patients who had malignant hypercalcaemia to assess host tolerance and the effect on serum calcium concentration. Ten of these patients also received intravenous rehydration or corticosteroids, or both. The serum calcium concentrations decreased significantly after treatment with aminohydroxypropylidene diphosphonate. Ten patients became normocalcaemic (normal range, adjusted for serum albumin, 2.25-2.75 mmol/l), two became hypocalcaemic, three showed decreases in serum calcium concentrations of more than 0.75 mmol/l, and one showed a decrease of more than 0.55 mmol/l. Only one patient had a minimum concentration greater than 2.77 mmol/l. Aminohydroxypropylidene diphosphonate was effective in metastatic and non-metastatic hypercalcaemia, and its hypocalcaemic effect was prolonged in some cases. There were no appreciable side effects. Single high dose infusions of aminohydroxypropylidene diphosphonate could replace conventional daily lower dose infusions, but the optimum frequency of high dose infusions remains to be determined.     

Vitamin D Intoxication Treated with Porcine Calcitonin

Porcine calcitonin was used to treat three patients with hypercalcaemia due to vitamin D intoxication. In two patients a rapid and sustained fall to normal in serum calcium occurred within three days, in the third patient normocalcaemia was achieved in seven days. In view of its rapid and sustained effect calcitonin may be of value in the urgent treatment of hypercalcaemia due to vitamin D intoxication.     

Hypercalcaemia due to dihydrotachysterol treatment in patients with hypothyroidism after thyroidectomy.

Hypercalcaemia is a recognised complication of hypothyroidism. We describe three patients who developed hypercalcaemia after thyroidectomy when thyroid supplements were discontinued. They were treated with thyroxine, dihydrotachysterol, and calcium after operation, and in all three cases serum calcium concentrations remained constant during combined treatment. Thyroxine treatment was discontinued several weeks before a radioiodine scan was performed; dihydrotachysterol and calcium were continued throughout. Serum calcium concentrations rose to hypercalcaemic levels in all cases. Elimination of dihydrotachysterol from plasma may be delayed in hypothyroidism, resulting in hypervitaminosis D. It is advisable to reduce the dose of dihydrotachysterol and to check serum calcium concentrations regularly in patients whose thyroid treatment is interrupted.     

Role of antidiuretic hormone in hyponatremia in patients with isolated adrenocorticotropic hormone deficiency.

We found symptomatic hyponatremia in four elderly patients in which serum sodium (Na) levels ranged from 101 to 122 mEq/l. All 4 patients had low levels of plasma adrenocorticotropic hormone (ACTH), serum cortisol, and urinary excretion of 17-OHCS, and poor responses of ACTH to exogenous insulin and antidiuretic hormone (ADH). Other pituitary hormones were all normal. They were therefore diagnosed as having isolated ACTH deficiency. Plasma ADH was relatively high despite hypoosmolality which was associated with the hyponatremia. Water loading test revealed impaired water excretion and poor suppression of plasma ADH. Replacement with 20-30 mg hydrocortisone completely restored the serum Na level and restored the plasma ADH level to the normal range in all 4 patients. Other factors such as decreased glomerular filtration, enhanced urinary Na loss and decreased Na intake were also included. These results indicate that there is marked hyponatremia and that in the presence of hypoosmolality the sustained secretion of ADH is the key factor in causing the impaired water excretion and hyponatremia in isolated ACTH deficiency.     

Renal Effects of Calcitonin

Porcine calcitonin in a slow-release gelatin vehicle was given by intramuscular injection to 10 patients—four with primary hyperparathyroidism, four with Paget''s disease, and two with carcinoma of the breast and hypercalcaemia. All cases showed a fall in serum calcium with an immediate rise in urine calcium. All except three patients with primary hyperparathyroidism showed a fall in serum phosphorus, but an immediate rise in urine phosphorus occurred in all cases. Urine hydroxyproline output fell in three patients with severe Paget''s disease. Urine sodium rose in all cases, but the effects on potassium, magnesium, water, and pH were not appreciably different from results obtained in four control subjects who were given the gelatin vehicle alone.The data suggest that calcitonin caused a decrease in the tubular resorption of calcium and phosphorus. The hypocalcaemic effect appeared to be due to a decrease in bone resorption in the patients with Paget''s disease but in the remaining cases could be accounted for in part or entirely by the rise in urine calcium.     

Calcium metabolism, serum thyroid-stimulating hormone, prolactin, and growth hormone in spontaneously hypercholesterolemic rats

We have shown previously that spontaneously hypercholesterolemic (SHC) rats exhibit abnormal bone metabolism with advanced bone resorption, which develops with age. In this study, we measured serum levels of growth hormone, thyroid-stimulating hormone, and prolactin in addition to several parameters of calcium metabolism and renal function in young (6-week) and old (24-week) SHC rats and compared these with age-matched Sprague-Dawley rats. In young SHC rats, urinary excretion of hydroxyproline and serum levels of calcium were significantly elevated and excretion of protein into urine and urea nitrogen in the serum were normal, suggesting that calcium metabolism was abnormal without kidney dysfunction at this age. Serum growth hormone and thyroid-stimulating hormone levels were markedly higher (20- to 30-fold and 4- to 5-fold, respectively) in young and old SHC rats, whereas serum prolactin levels were similar. A high level of serum thyroid-stimulating hormone was associated with elevated levels of thyroxine and triiodothyronine in young SHC rats, but not old ones. These results demonstrate that the rat exhibits abnormalities in endocrine function as well as calcium metabolism preceding the occurrence of renal dysfunction.     

Immobilization hypercalcaemia in patients on regular haemodialysis.

Immobilization of normal people causes reabsorption of calcium from bone, a small rise in serum ionized calcium, and, rarely, frank hypercalcaemia. The hazard is increased when patients with renal osteodystrophy are immobilized because of pathological fractures.     

Somatomedin, transferrin and amino-acids in serum following injection of human growth hormone in children with growth disease

17 children with growth retardation (12 with idiopathic hypopituitary dwarfism, 2 with craniopharyngioma and 3 constitutionally short) were studied for three days following a single intramuscular injection of human growth hormone. Somatomedin activity was bioassayed using both sulphate incorporation into chick embryo cartilage and thymidine uptake by human lectin-activated lymphocytes. In hypopituitary patients it showed a significant response, maximal 24 hours after the injection, and significantly correlated for the two bioassays. The aminoacid content of the incubation medium used for thymidine bioassay appeared as an important factor: both glutamine and nonessential aminoacids are required to obtain significant stimulation by low serum concentrations, thus increasing the sensitivity of the assay but reducing the differences between normal and hypopituitary sera. Transferrin levels in serum were significantly lower in hypopituitary dwarfs. They did not rise in the three days following hGH. Aminoacid levels were lower in idiopathic GH deficient patients than in other groups, and did not show short term increase in the fasting samples collected after hGH administration.     

Surgical treatment of primary hyperparathyroidism in the elderly.

Twelve patients aged over 70 with primary hyperparathyroidism (persistent hypercalcaemia and raised serum parathyroid hormone concentrations) underwent parathyroidectomy, which was well tolerated by all. After operation serum calcium concentrations returned to normal and the commonest symptoms before operation (muscle weakness, malaise, and mild to severe dementia), although not related in severity to the degree of hypercalcaemia, improved. Mental function was greatly improved. The findings suggest that primary hyperparathyroidism should be sought in any elderly patient with hypercalcaemia and that more such patients with the diagnosis should be considered for parathyroidectomy irrespective of age.     

Familial hypocalciuric hypercalcaemia and acute pancreatitis.

Four families with familial hypocalciuric hypercalcaemia were studied. The probands presented with abdominal pain, which in three was due to acute pancreatitis; in two the condition was life threatening. Serum concentrations of calcium, magnesium, phosphate, and immunoassayable parathyroid hormone, urinary calcium excretion, and the rate of renal tubular reabsorption of phosphate were measured; the findings were compared with results in 10 patients with primary hyperparathyroidism matched for serum calcium concentration to establish differences between the diseases. Familial hypocalciuric hypercalcaemia should be suspected in patients with hypercalcaemia in whom daily urinary calcium excretion is below 5 mmol (200 mg) provided renal insufficiency, vitamin D deficiency, and ingestion of drugs that reduce calcium excretion have been excluded. Most cases appear to run a benign course, but some may suffer considerable morbidity. Surgical treatment should be reserved for patients with severe complications, when all parathyroid tissue should be removed.     

The Effects of Probenecid and Thiazides and Their Combination on the Urinary Excretion of Electrolytes and on Acid-base Equilibrium

The effects of commonly used therapeutic doses of hydrochlorothiazide and probenecid, given singly and in combination, on the urinary excretion of monovalent and divalent ions and on acid-base equilibrium were studied in four patients with idiopathic hypercalciuria.Probenecid had no effect on the urinary excretion of monovalent ions but resulted in a sustained increase in the urinary excretion of calcium, magnesium and citrate and a temporary increase in the urinary excretion of ammonium, in addition to its well-known effects on uric acid metabolism. A temporary fall in serum phosphorus levels was also observed.Probenecid also modified the response to hydrochlorothiazide in that the urinary excretion of calcium, magnesium and citrate was greater during combined therapy than when hydrochlorothiazide was administered alone. Probenecid prevented or abolished the increase in serum uric acid levels associated with the use of thiazide but did not modify the effects of hydrochlorothiazide on the urinary excretion of sodium, chloride, potassiu, phosphorus, ammonium, titratable acid and bicarbonate.     

The effects of fasting and refeeding on serum parathormone and calcitonin concentrations in young and old male rats.

Although fasting and refeeding reveal the existence of age-related changes in carbohydrate and lipid metabolism, the effects of aging on mineral metabolism in refed animals are unknown. We therefore investigated hormonal regulation of calcium metabolism in young (4 months) and old (26 months) male rats fasted for 48 hours and then refed for 4 or 24 hours. Serum concentrations of total and ionized calcium and parathormone were similar in control young and old rats. Serum calcitonin level was higher, and the concentrations of albumin and inorganic phosphate and alkaline phosphatase activity were lower in fed old rats. In young fasted rats, the serum ionized and total calcium was decreased, and phosphate concentration was increased. In old rats, fasting resulted in the increase of serum parathormone level. Fasting reduced serum alkaline phosphatase activity to a similar extent in both age groups. In young rats, refeeding for 24h normalized serum calcium and phosphate levels and alkaline phosphatase activity, and decreased serum concentrations of PTH and calcitonin. In old refed rats, serum calcitonin concentration was raised by 77% compared to fed or fasted animals, whereas parathormone levels were normalized. Our results indicate that old fasted or refed rats maintain normal serum calcium concentration in a different way than young animals, possibly through the increase in serum levels of parathormone and/or calcitonin. Thus, dietary manipulations such as fasting and refeeding constitute an interesting model for the investigation of the effects of aging on the hormonal regulation of serum calcium level.     

Mechanism of malignant hypercalcaemia in carcinoma of the breast.

To investigate the mechanisms of hypercalcaemia in carcinoma of the breast, 22 patients with hypercalcaemia due to metastatic carcinoma were studied and the findings compared with those obtained in normal subjects and patients with benign and malignant breast disease without hypercalcaemia. As expected, patients with metastases of bone showed biochemical evidence of increased bone resorption. Whereas all patients with hypercalcaemia had skeletal metastases, not all patients with skeletal metastases had hypercalcaemia despite considerable degrees of bone resorption. The presence of hypercalcaemia was associated with a significant increase in renal tubular reabsorption of calcium (p less than 0.001) and decreased reabsorption of phosphate (p less than 0.001) despite adequate rehydration of patients. These studies suggest that increased renal tubular reabsorption of calcium, possibly mediated by a humoral factor with activity similar to that of parathyroid hormone, contributes appreciably to the hypercalcaemia of malignant breast disease.