Effect of conventional and newer forms of treatment on calcium absorption in osteoporosis

Studies carried out in this Research Unit and by others have shown that patients with osteoporosis absorb less calcium from a high calcium intake than do patients without osteoporosis. To determine whether various treatment modalities would increase the intestinal absorption of calcium, the effects of conventional and new methods were investigated. Tracer doses of 47Ca were given orally to determine the absorption of calcium. Calcium balances were also determined. Estrogen decreased urinary calcium and testosterone increased the nitrogen balance. Vitamin D and strontium increased the urinary calcium but did not increase calcium absorption. Of the newer compounds, fluoride did not affect calcium absorption but decreased urinary calcium. Phosphate had a similar effect. Infusions containing up to 15 mg calcium/kg, given for 6 or 10 days, increased the retention of calcium but did not increase its absorption.

Anabolic effect of low doses of a fragment of human parathyroid hormone on the skeleton in postmenopausal osteoporosis

Parathyroid hormone, injected daily in low dosage, exerted anabolic effects on the human skeleton, just as it does in the rat. Four postmenopausal women with primary osteoporosis were treated for six months with a synthetic fragment of human parathyroid hormone (hP.T.H. 1-34), given as a daily injection of 100 mug. This treatment caused a remarkable acceleration of bone turnover, indicated both by isotopic tracer and histological methods. At this normocalcaemic dose level, the increases in bone formation outweighed increases in resorption. Three of the four patients showed more positive calcium balances, and mean increases in calcium and phosphorus balances were statistically significant for the group as a whole, the changes being principally due to increased intestinal absorption of both elements. Many modifications of the present method of hormone administration are possible which could further increase the preponderance of anabolic effects. These results suggest that low doses of hP.T.H. 1-34, alone or in combination with other agents, may prove useful in the treatment of osteoporosis.

Acute and chronic estrogen effects upon serum somatomedin activity, growth hormone, and prolactin in man

Estrogen (E) reduces bioassayable GH-dependent serum somatomedin (SM) activity in acromegalics without affecting plasma growth hormone (GH) levels and inhibits the rise of SM activity normally produced by GH administration in GH-deficient subjects. We have now investigated the effect of E administration on serum SM activity and on plasma GH and prolactin (PRL) in 6 adult male subjects without pituitary pathology. Chronic E administration (ethinyl estradiol 0.5 mg/day for 7 to 70 days) reduced serum SM activity by 40 to 62% in each of 4 subjects (P less than 0.02 to less than 0.001). In 3 of the subjects, basal GH levels increased by 75 to 300% (P less than 0.05 to less than 0.001) and basal PRL levels increased by 90 to 200% (P less than 0.01 to less than 0.001). While iv administration of normal saline did not significantly affect either SM or GH, iv administration of E (bolus injection of 25 mg conjugated estrogens, USP) to 5 subjects resulted in: a) a 46 to 80% decrease in serum SM activity in all subjects, proceeding with an apparent half-life of 2 hours, becoming significant (P less than 0.05) at 2 hours (1 subject) to 3 hours (4 subjects), maximal at 6 hours, and persisting for 12 to 24 hours; b) GH elevation to 3 to 16 times baseline level (P less than 0.01) at 2 to 3 hours in 4 subjects; and c) no significant change of PRL levels in any subject. The mean GH response to iv E was maximal at a time (2 hours) when the mean SM activity had decreased only 20% and subsided well before the nadir of SM activity. The one patient without GH response to chronic or acute E administration may have been affected by absorption of triamcinolone being applied topically during the study. These results demonstrate that in males with normal pituitary function, E reduces serum SM activity, enhances basal GH and PRL secretion, and, upon iv injection, stimulates acute GH release. Although opposite chronic E effects upon GH and SM activity support a putative negative SM-GH feed-back mechanism, iv E administration apparently provokes acute GH release by a different mechanism. The half-life of serum SM activity in the human is probably much shorter than previously estimated.

[Relation between urinary cyclic AMP, PTH and histomorphometric resorption parameter. A study of 44 human iliac crest bone biopsies]

Daily urinary cyclic AMP (AMPcU) has been compared to pth plasma level and to bone resorption parameters in 44 cases of metabolic bone disease. In 14 cases of primary hyperparathyroidism, AMPcU was always increased likewise in 4 cases of osteomalacia with secondary hyperparathyroidism. On the whole series of cases a significant correlation has been found (1) between PTH plasma level and AMPcU and (2) between bone resporption surfaces and AMPcU. Conversely, no correlation between PTH and periosteocytic lacunae size, nor between AMPcU and periosteocytic lacunae has been found.

A new method for calculating the accretion rate of bone calcium and some observations on the suitability of strontium-85 as a tracer for bone calcium

1. A new method for calculating the accretion rate (A) of bone calcium is proposed, based on an impulse analysis of 47Ca data. The method is free of most of the assumptions inherent in previous methods of analysis and appears to give more accurate estimates. 2. In fourteen normal subjects and twelve patients with metabolic bone disease, measurements of A by the new method gave very similar results to the mineralization rate calculated by the method of Burkinshaw et al. (1969). Analysis of twelve studies performed by Neer et al. (1967) gave good agreement with their five compartment model. A close relation between A and Marshall's (1964) A5 was observed, but the latter gave systematically higher results. 3. In sixteen studies both 47Ca and 85Sr were injected simultaneously. Although there were no systematic differences between the values of A for the two tracers, the differences between individual values were greater than the known experimental errors.

The distribution of cortical and trabecular bone mass along the lengths of the radius and ulna and the implications for in vivo bone mass measurements

The amounts of cortical and trabecular bone mineral mass were measured by means of microdissection and an ashing technique at approximately 2.5 mm intervals along the most distal 12 cm of radii and ulnae from four women aged 21, 43, 63, and 85. The data show that the distributions of mineral mass and percentage of trabecular bone are similar in both bones. At sites in the radius and ulna commonly used in the photon absorptiometric method of bone mineral mass measurement the percentage of trabecular bone varies between 10% and 50%. The percentage of trabecular bone in the most distal 10% of the length of the radius and ulna remains approximately constant with age but the percentage in the segment which lies between 30% and 40% of the length, measured from the styloid process, increases with age.

Factors affecting the distribution of zinc in the human skeleton

The zinc content of trabecular and cortical bone was measured in 28 femora obtained at autopsy. The ratios of calcium to zinc, phosphorus and magnesium were determined and their relation to age and vertebral density was investigated. The calcium/zinc ration was significantly higher in cortical as opposed to trabecular bone, whereas the calcium/phosphorus ratios were similar. There was a significant decrease in the calcium/zinc ratios of both trabecular and cortical bone with age and the former was directly related to vertebral density. The calcium/phosphorus ratios of trabecular and cortical bone did not vary significantly with age or vertebral density. Magnesium/zinc ratios tended to parallel the calcium/zinc ratios. The calcium/magnesium ratios were significantly higher in cortical as opposed to trabecular bone. None of these ratios appeared to be affected by the sex of the subject. These findings suggest that changes in skeletal zinc content with age are related to alterations in bone morphology, and that osteoporosis in man develops in association with zinc accumulation rather than zinc deficiency.

Treatment of osteoporosis of ageing with 1alpha-hydroxycholecalciferol

Seven patients with osteoporosis of ageing were treated with synthetic 1alpha-hydroxycholecalciferol (1alpha-H.C.C.) for 3-4 months. The compound was given at a daily oral dose of 2 mug together with an oral supplement of 1 g of calcium. Clinically there was a striking improvement in the patients' physical fitness. Increased bone formation and mineralisation were seen on iliac-crest bone biopsy, and this was supported by an increased osteoblastic activity demonstrated by histochemical measurement of alkaline-phosphatase activity. Bone histology furthermore showed a reduced bone resorption, which was supported by a reduced urinary excretion of total hydroxyproline. Photon absorptiometry of the forearm accorded with the histological findings, showing a significant increase in the bone mineral content. Serum-calcium rose in all patients, one developing a severe transitory hypercalcaemia. The urinary excretion of calcium and magnesium increased significantly. The serum concentrations of 25-hydroxycholecalciferol and parathyroid hormone were not significantly affected by the treatment. It is concluded that 1alpha-H.C.C. is an effective tool in the treatment of senile osteoporosis.

[Test for hypocalcemia due to calcitonin in the normal subject and in patients with osteoporosis or Paget's disease. Preliminary results]

The authors report the variations in calcaemia and in circulating immunoreactive PTH produced by the intramuscular injection of 5 units of porcine calcitonin in normal subjects and in patients suffering from osteoporosis or Paget's disease. After having determined the levels of 25-hydroxy-vitamin D circulating in the different groups, the authors note that comparison of these variations makes it possible to regroup the different types of reaction following the injection of the hypocalcaemic hormone. In patients suffering from pure osteoporosis, hypocalcaemia was slow to appear, was of moderate intensity, but was prolonged. The osteoporo-malacia patients did not produce a specific reaction and certain of them appeared "insensitive" to calcitonin. Results obtained in patients with Paget's disease confirm the hypocalaemic action of calcitonin even at a low dosage. With this test, the authors hope to contribute to studies of demineralizing affections and to overcoming them.

The effect of fluoride alone or fluoride followed by calcium and vitamin D on disuse osteoporosis of the rat tail vertebrae

The therapeutic effect of fluoride alone or fluoride followed by calcium and vitamin D administration on the osteoporosis induced by immobilization of the rat tail vertebrae was investigated. Tail immobilization was carried out by musclectomy and tendectomy. After 60 days of immobilization, the vertebrae were examined for bone mass, breaking strength, ash percentage and Ca, P and F content. NaF or Ca and vitamin D as separate treatments improved the osteoporosis induced by immobilization. The effects of NaF treatment were more pronounced than those of Ca and vitamin D. NaF and NaF followed by Ca and vitamin D produced a similar degree of improvement in breaking strength. The fact that fluoride and calcium and vitamin D were administered separately and sequentially may explain the absence of a synergistic effect.

Bone mineralization in the distal forearm of hemiplegic patients

Bone mineral content was measured by single photon absorptiometry using a modified bone densitometer (Packard) with 125I as the source. In 42 hemiplegic subjects, matched for sex and age, the bone density was compared bilaterally on the radius and ulna 2 cm and 4 cm above the wrist. The nonparalyzed side served as a control for the paralyzed side. The results indicate a consistent, general loss of bone mineral on the paralyzed side compared with the nonparalyzed side. The extent of demineralization in females was greater than in male subjects. Right-dominant left-paralyzed patients showed a greater loss of bone density than right-dominant right-paralyzed subjects. The absorption ratio of the paralyzed vs the nonparalyzed sides revealed that there was a 5.3% and 7.4% decrease in the average bone density at 4 and 2 cm above the wrist, respectively. There was a progressive loss of bone mineral content relative to time after the onset of paralysis, amounting to an average of 6.4% approximately three months after the onset of injury. It was estimated that before the onset of paralysis there was an excess of bone mineral on the dominant vs the nondominant side of +5.4% and +3.2% for males and females, respectively.

On an attempt to treat primary and secondary osteoporosis with human growth hormone

Three male patients with severe osteoporosis were treated with human growth hormone. One of them had a primary osteoporosis, the two others osteogenesis imperfecta. The duration of therapy was 8 to 15 months and average doses per day were 1.45 to 2.3 mg. While clinical and 47calcium kinetic data failed to prove marked influences of the treatment, histomorphometry of bone biopsies showed indisputable changes. There was an increase of periosteal new bone formation as well as of intracortical bone resorption, while at the same time the relative activity of osteoblasts on endosteal surfaces showed a significant increase.

Regulation of circulating parathyroid hormone levels: normal physiology and consequences in disorders of mineral metabolism

A review of the chemistry, the biosynthesis, the regulation of the secretion and the metabolism of parathyroid hormone (PTH) provides a background to problems related to the determination of immunoreactive PTH levels in the blood of normal subjects and of patients suffering from disorders of mineral metabolism. Immunoreactive PTH measurements have to be interpreted in the light of the immunoheterogeneity encountered and the occurrence of several circulating PTH species with different molecular weights and immunological properties.

Effect of the diphosphonate EHDP on bone mineral metabolism during prolonged bed rest

The effect of disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDPTM) on bone mineral metabolism was tested in 4 healthy young men during 20 weeks of continuous bed rest. Two subjects received an oral dose of 5 mg/kg/day and the other 2 20 mg/kg/day. The low dose had two minor effects: the increase in bone accretion rate which usually occurs during bed rest was prevented, and there was an accentuation of the bed rest induced increase in hydroxyproline excretion. Skeletal mineral loss, assessed by calcium balance measurements and gamma ray absorptiometry of the calcaneus, occurred at the rate previously noted in untreated control subjects. Two types of drug effect were apparent at the higher dosage: one was immediate and sustained--a rise in serum phosphorus concentration and a fall in serum alkaline phosphatase activity. The other was delayed and progressive--a decline in urinary hydroxyproline excretion and in the rates of bone accretion and resorption. Skeletal mineral loss may have been affected; the usual negative mineral balance developed during the first half of the study, then disappeared during the last few weeks. However, gamma ray absorptiometry revealed no attenuation of the calcaneal mineral losses.

Relationship between local and total bone mass in osteoporosis

The relationship between total body calcium (TBC) and local bone calcium mass (BCM) was studied in a group of osteoporotic patients (12 females and two males) with a wide range of body size. Two methods were used to estimate BCM: photon absorptiometry and radiographic morphometry. TBC was estimated by total-body neutron-activation analysis. Since 99 percent of TBC is located in the skeleton, it was assumed that TBC was essentially a measure of total skeletal (calcium) mass. TBC ranged from 482 to 1076 g. High correlations with r values from 0.84 to 0.94, p less than 0.001, were found between TBC and BCM measured by absorptiometry at six different sites of radius, ulna, and humerus. Additionally, high correlations with r values from 0.89 to 0.95, p less than 0.001, were found between BCM at the distal tenth of the radius and BCM at the five other sites. A high correlation was also found between body height and TBC, but partial correlations indicated that this accounted for very little of the correlation between TBC and BCM. In contrast to the above, correlations between BCM determined by radiographic morphometry and TBC were weak or nonsignificant. When TBC and BCM were expressed as percent of their mean value, the slopes of the estimating equations, describing the relationships between TBC and BCM, were essentially the same, but significantly less than one, which is the value of the slope expected if TBC and BCM had changed at the same relative rate. From these relationships, we conclude (1) that the rate of change in BCM was similar in the six sites examined, and (2) that the rate of change in these six sites was relatively more rapid than the change in total body calcium. Whether the change in rate of BCM was related to rate of increase during attainment of maximum BCM or subsequent rate of loss of BCM or both remains to be determined.

Long-term observations on the loss of bone mineral following colles' fracture

Seventy-four women were studied at various points in time between 1 month and 12 years after a fracture of the distal end of the radius--Colles' fracture. In 50 cases the maximum loss of bone after fracture was considered to have taken place in that more than 4 months had elapsed since the accident. The bone mineral content was measured in both forearms with gamma absorptiometry. It was demonstrated that the degree of post-traumatic osteoporosis, calculated as the difference between the values obtained for the injured and the uninjured arms, decreased with time. The difference between the arms was greater in peri- and early postmenopausal and in very old women suggesting that these groups had lost more bone and/or been less able to restore lost mineral with time.

Total body retention of orally administered 47-calcium in primary hyperparathyroidism

Using a whole body radiation detector, we have measured the total body retention of 47-Ca 7 days after oral administration of the isotope to patients with various disorders of calcium metabolism. The percent retention of 47-Ca given with 90 mg of unlabeled (carrier) calcium varied with the calcium metabolic status as follows: normals (n equals 14), 33-43 percent (mean 38); primary hyperparathyroidism (n equals 28), 32-74 percent (mean 52); idiopathic hypercalciuria (n equals 9), 34-49 percent (mean 42); and hypercalcemia of other etiology (n equals 3), 23-26 percent (mean 25). Almost half (13/28) of those with hyperparathyroidism showed a retention above 55 percent, distinguishing them from subjects with idiopathic hypercalciuria. Retention of 47-Ca correlated poorly with clinical measures of severity of hyperparathyroidism. When isotope was diluted with a smaller amount of carrier calcium (20 mg), retention was increaseed in normals (n equals 5) to 46-54 percent (mean 50) and in hyperparathyroidism (n equals 5) to 64-87 percent (mean 73). After surgical cure of hyperparathyroidism retention of isotope returned toward normal in 5 of 7 subjects. Whole body retention of orally administered 47-Ca may prove useful in detecting hyperparathyroidism in subjects with mild hypercalcemia or hypercalciuria.

Retention of fluoride with time in man

Fluoride retention is high during fluoride supplementation and increases with increasing fluoride intake. When large amounts of fluoride were given for several months the retention of fluoride was about the same as in the initial phase of fluoride supplementation, whether the supplemental dose of fluoride was 10, 20, or 45 mg per day. The rapid return of the fluoride balance to control values after the high fluoride intake was discontinued indicates that there is not only a tendency for continued retention of fluoride during the high fluoride intake but also after large amounts of fluoride have already been retained.

The metabolic balance technique: a critical reappraisal

Twenty-six metabolic balance studies (MBS) of Ca, Mg, and P have been conducted in 11 postmenopausal women with osteoporosis and in 4 patients suffering from Paget's disease of bone. Subjects were given a liquid formula diet (LFD) matched as closely as possible to the patient's home diet. Studies lasted for 25 days, separated into 5-day periods by a carmine marker combines with Cr2O3 as continuous fecal marker. The balance studies were combined with a tracer technique using 47Ca to detect a possible loss of Ca by perspiration. The reliability of analytical methods necessary for mineral balances was tested. In 22 of the 26 MBS a steady state (SS) reflecting the patient's regular living conditions was demonstrated, while a non-SS situation possibly due to changes of physical activity was seen in four instances. The overall precision and accuracy of this balance method for Ca and P was found to be better than plus or minus 50 mg/day after four periods and plus or minus 40 mg/day after five periods, as related to an average daily intake of 920 mg Ca and 1230 mg P. For Mg (intake 190 mg/day), a precision of plus or minus 10 mg/day was recorded. The dermal loss of Ca was found to be less than 20 mg/day. As shown for Ca, Mg and P, the precision of a balance study is only little enhanced when the investigation is continued for more than four periods. At the present time is not possible to predict non-SS situations before starting such a study but a simple formula is proposed to detect those which were not performed under SS conditions.

Abnormalities in mineral metabolism suggestive of parathyroid over-activity in rheumatoid arthritis

A three-part study on mineral metabolism in patients with classical rheumatoid arthritis is described. In the first two parts, biochemical abnormalities were revealed suggestive of parathyroid over-activity, and in the third part, observation on calcium absorption provides a hyperparathyroid pattern. The importance of these findings in relation to demineralisation of bone in rheumatoid arthritis is discussed.

Calcium metabolism in renal failure

Osteodystrophy is almost universally present in chronic renal failure. Mild, but detectable, abnormalities--especially in parathyroid hormone (PTH) secretion--occur even when the glomerular filtration rate is greater than 30 cc/min. Osteomalacia is common in areas in which vitamin D intake and exposure to sunlight are minimal; when these factors are plentiful, osteitis fibrosa predominates. Osteoporosis is seen with increasing frequency in hemodialyzed patients. Nonosseous complications of secondary hyper-parathyroidism include hypercalcemia, metastatic calcification and pruritus. The most important factor in the medical therapy of osteodystrophy is control of serum phosphate levels. Next, a positive calcium balance must be provided either by giving vitamin D as dihyrdotachysterol, raising dialysate calcium or administering calcium orally. Parathyroidectomy is sometimes indicated, especially when the patients are transplant candidates and manifest hypercalcemia. Whether or not transplant is contemplated, patients with persistently high calcium-phosphate products, severe metastatic calcification or rapidly progressive osteodystrophy should be considered for parathyroidectomy. Newer, experimental vitamin D preparations, such as 1,25-dihydroxycholecalciferol or 1-alpha-hydroxycholecalciferol, should improve the managemet of patients with renal osteodystrophy and decrease the need for parathyroidectomies.

Measurement of bone mineral content in vivo using photon absorptiometry

Progress in evaluating treatment of systemic bone disease has been hampered in the past by lack of precise in vivo quantitative techniques. Recently a method has been developed for measurement of bone mineral content (BMC), based on bone absorption of low-energy monochromatic radiation. This paper discusses a technique of photon absorptiometry using (125)l as a collimated point source. The technique is simple, with accuracy and precision within 2%.BMC and bone width (W) were measured in the distal radius of 359 normal subjects ranging in age from 5 to 82 years. A "normal" curve of BMC/W with age as the independent variable was then obtained from this population and was constructed for each sex. A positive correlation of BMC/W with height and body weight was found in a group of normal males.A series of patients with osteoporosis or malabsorption, or undergoing hemodialysis or steroid treatment, was then assessed in order to demonstrate changes in BMC/W that may occur secondary to disease or disturbances in calcium metabolism. Many of these patients were found to have a BMC/W below the normal mean value for their age and sex.

[The oral Ca47 test and cynamics of Ca47: comparative evaluation in the study of the digestive absorption of calcium in man]

The intestinal absorption of calcium is one of the most important processes regulating calcium metabolism. Its measurement requires the estimation of dietary and faecal calcium over a period of one week, but this procedure is frequently liable to error. The availability of two isotopic procedures contributed to the successful pursuit of measuring intestinal absorption of calcium. In the first procedure the indirect assessment of calcium absorption is based on the kinetic study of plasma radioactivity curve after an intravenous dose of radiocaldium at the same time with a calcium balance study over a period of 6 days, In the second isotopic procedure the calcium absorption is directly calculated from the plasma radioactivity and residual faecal activity following an oral dose of radioactive calcium. We have investigated by the two methods 25 patients (one normal subject and 24 affected by a variety of clinical disorders of calcium metabolism). The excellent agreement, statistically significant, between the data obtained by the two methods suggests that both procedures are adequate to assess intestinal absorption of calcium in man.

Effects of therapy on rate of absorption of calcium from gut in disorders of calcium homoeostasis

A development of the double-tracer calcium absorption test, in which a function is derived for single-passage entry rate from the gut with time, has been assessed in various disorders of calcium homoeostasis. Single tests are diagnostically useful in calcium malabsorption but because of the wide spectrum of normal values a single test can only moderately enhance the accuracy of the diagnosis of hypercalcaemic states made primarily by other methods. On the other hand serial studies in the same subject can be much more informative because the test is normally highly reproducible if conditions are unchanged. Serial studies play an important part in assessing the efficacy of established methods of treatment in disorders of calcium homoeostasis and should be particularly helpful in studying the effects of new forms of therapy on the absorption process.