David M. Slovik

Anabolic effect of human parathyroid hormone fragment on trabecular bone in involutional osteoporosis: a multicentre trial.

After baseline studies, 21 patients with osteoporosis were treated with human parathyroid hormone fragment (PTH 1-34) given as once-daily subcutaneous injections for 6-24 months. The dose used did not cause hypercalcaemia even in the first few hours after injection. Calcium and phosphate balances improved in some patients, but there was no significant improvement in the group values. There were, however, substantial increases in iliac trabecular bone volume: the mean increase, confirmed by repeat blind measurements, was 70% above mean baseline volume. The new bone was histologically normal. Those patients who had the largest increases in 47Ca-kinetic and histomorphometric indices of new bone formation showed the greatest increases in trabecular bone volume, suggesting that treatment with human parathyroid hormone fragment caused a dissociation between formation and resorption rates that was confined to trabecular bone. Since vertebrae are four-fifths composed of trabecular bone, this hormone fragment may prove useful in treating patients with the crush fracture syndrome.

Deficient Production of 1,25-Dihydroxyvitamin D in Elderly Osteoporotic Patients

There is uncertainty about the adequacy of renal secretion of 1,25-dihydroxyvitamin D(1,25-(OH)2-D) in elderly patients with osteoporosis. To investigate this uncertainty, we stimulated secretion of 1,25-(OH)2-D with a 24-hour intravenous infusion of synthetic human parathyroid hormone fragment 1-34 and compared the results in normal young adults and elderly patients with untreated osteoporosis. Serum levels of 1,25-(OH)2-D were similar in both groups (49 +/- 10 and 42 +/- 9 pg per milliliter [116 +/- 24 and 99 +/- 21 pmol per liter]) before the infusion. However, during the 24-hour infusion, serum levels nearly doubled (P less than 0.01) in the normal volunteers but did not change significantly in the patients. Serum ionized calcium increased and serum inorganic phosphate decreased similarly in both groups during the infusion (P less than 0.05). Although the present study does not establish whether deficient 1,25-(OH)2-D secretory reserve is an effect of age or of osteoporosis, it is possible that such a deficiency will explain the inability of elderly osteoporotic patients to adapt to the low-calcium diets common in this age group. If so, this phenomenon may play a part in the pathogenesis of age-related osteoporosis.

Short-term effects of synthetic human parathyroid hormone-(1--34) administration on bone mineral metabolism in osteoporotic patients.

Since studies in animals and humans have shown that parathyroid hormone can stimulate bone formation and increase trabecular bone, and patients with primary and secondary hyperparathyroidism may exhibit osteosclerosis, we evaluated the effect of short-term administration of human parathyroid hormone, hPTH-(1--34), in patients with osteoporosis. Six patients with osteoporosis underwent detailed studies including blood and urinary measurements of calcium, phosphate, and magnesium; 47Ca kinetic studies; and 18-d balance studies before and during the short-term administration (3--4 wk) of a daily subcutaneous injection of hPTH fragment 1--34 given as 450 or 750 U/dose. The mean fasting plasma calcium values rose slightly after hPTH-(1--34) administration, primarily in the high-dose group. There was no difference in the mean fasting plasma inorganic phosphate levels. The mean daily urinary excretion of calcium and phosphate was significantly increased in patients given the higher dose. In patients given 750 U, net intestinal calcium absorption increased, phosphate absorption increased, calcium balance improved, and phosphate balance improved. In patients given 450 U, calcium balance and phosphate balance worsened. 47Ca kinetic studies showed a minimal increase in bone accretion rate, a decrease in the mean transit time of calcium in the exchangeable pools, and a decrease in the exchangeable-pool size. In all six patients there was an increased renal clearance of 47Ca as a result of hPTH-(1--34) administration. These studies indicate that low doses of parathyroid hormone may promote bone formation, whereas higher doses clearly have an adverse effect on the skeleton.

Treatment of postmenopausal osteoporosis with daily parathyroid hormone plus calcitriol.

An ideal treatment for osteoporosis would increase bone strength by increasing the amount of mineralized lamellar bone, the thickness of cortical bone, and the connectivity of trabecutar bone, and would maintain bone remodeling and repair mechanism so that microfractures could be repaired rapidly before they accumulated and caused major structural collapse. Furthermore, an ideal treatment would increase bone mass and bone strength to normal, not just incrementally. The failure of estrogens, androgens, anabolic steroids, calcitonin, fluoride, or cyclic etidronate to produce such effects has led most physicians and many investigators to suppose that osteoporosis in incurable. Parathyroid hormone stimulates bone formation and resorption indirectly, by stimulating the local secretion of insulin-like growth factor I (IGF-I), other growth factors, cytokines, and/or proteases in bone. By manipulating the pharmacological profile of parathyroid hormone in blood, it is possible to uncouple these anabolic and catabolic effects and thus augment bone mass. For example, the subcutaneous injection of human parathyroid hormone or its 1-34 fragment (hPTH 1-34) increases the mass and strength of trabecular and cortical bone in experimental animals, while increasing bone remodeling rates and the total amount of mineralized lamellar bone [1-6]. In many but not all osteoporotic elderly patients, PTH 1-34 fragment fails to increase blood levels of 1,25dihydroxyvitamin D (calcitriol) and fails to increase this problem we have given hPTH 1-34 and calcitriol simultaneously. Our positive but uncontrolled studies in osteoporotic men have been reported previously [10]. We recently completed a controlled trial in osteoporotic postmenopausat women. Thirty such women were stratified according to age and spinal trabecular bone mineral density, and divided into two comparable groups. One received calcium supplementation of 1000-2000 mg/day as the carbonate. The other received 400-500 units/day hPTH 1-34 plus 0.25 gg/day calcitriol. No patient received any other treatment for osteoporosis. In all patients, osteomalacia was excluded by iliac crest biopsy and causes of osteoporosis other than estrogen deficiency and age were excluded by routine clinical methods. Spinal trabecular bone mineral density increased 32%, while total spinal bone mineral density measured by dual-photon absorptiometry increased 12%, during 1-2 years of experimental treatment. There were no significant changes in these measurements in the calcium-treated controls. Cortical bone mineral density decreased 1.7% in the calcium-treated patients and 5.7% in the experimentally treated patients. The changes in cortical bone mineral density in the women given PTH and calcitriol occurred during the first 12 months of treatment; thereafter, cortical bone mineral density did not decline further. There were no untoward effects and the treatment was well tolerated, though transient local skin reactions to the peptide or its salt required early cessation of treatment in one patient. Hypercalcemia and hypophosphatemia were avoided and creatinine clearance remained stable. We believe the non-progressive decline in cortical bone density observed in the experimentally treated women reflects increased bone remodeling. It is of note that cortical bone density did not decline when the same treatment program was given to osteoporotic men [10]. Fnrthermore an alternating dose regimen of PTH and calcitriol previously utilized by us increased spinal trabecular bone mineral density in osteoporotic postmenopausal women without reducing cortical bone mineral density in the forearm [ 11]. After 6-12 months, spinal bone mass in our patients stopped increasing for unclear reasons. Further studies are under way to explain and/or circumvent this limitation.

Quantitative computed tomography for spinal density measurement. Factors affecting precision.

Quantitative computed tomography (QCT) was performed in duplicate on 84 patients to test the short-term precision of the technique. Statistical analysis of the data revealed that precision was not a function of spinal density. It appeared to be worse in osteopenic individuals only when expressed as a percentage. Precision was slightly better in male than in female patients. There is a 90% likelihood that a duplicate measurement will fall within 20 CT units of the first determination in female patients and within ten units in male patients.

PARATHYROID HORMONE AND 25‐HYDROXYVITAMIN D LEVELS IN GLUCOCORTICOID‐TREATED PATIENTS

Abnormalities in parathyroid hormone (PTH) secretion or vitamin D action or metabolism have been suggested as pathogenetic factors in the bone disease associated with chronic glucocorticoid therapy. We have found normal plasma PTH values in forty‐eight adult asthmatic patients on chronic glucocorticoid therapy, twelve asthmatics treated without glucocorticoids and ten adults on short‐term, high‐dose glucocorticoid therapy for non‐asthmatic illnesses. The mean serum 25‐OHD level in the glucocorticoid‐treated asthmatics was not significantly different from a disease control group of asthmatic patients not on glucocorticoids, but nine such patients had abnormally low 25‐OHD levels. Our results indicate that in asthmatic patients on chronic glucocorticoid therapy: (1) PTH and 25‐OHD values are usually normal regardless of dose or duration of therapy and (2) there is a subset of patients with low 25‐OHD values which may reflect unusual sensitivity to glucocorticoids.

Calcium-47 kinetic measurements of bone turnover compared to bone histomorphometry in osteoporosis: The influence of human parathyroid fragment (hPTH 1-34) therapy

Abstract Nineteen patients with involutional osteoporosis have been studied by means of combined 47 Ca kinetic and calcium balance studies and morphometric analysis of iliac crest bone biopsies taken after double tetracycline labelling. Fifteen of them, together with three additional patients, were restudied after at least six months treatment with human parathyroid hormone fragment (hPTH 1-34). A close inverse relationship was found in the untreated patients between trabecular resorption surfaces (RS%) and calcium balance. The kinetically determined resorption rate showed a significant positive correlation with RS%, while the product of surface osteoid (SO%) and calcification rate (CR), determined from the tetracycline double label, correllated significantly with the 47 Ca accretion rate. When the data from the patients on treatment were examined the relationship between calcium balance and RS% persisted; but the increased scatter in values for trabecular bone volume (TBV%) following the positive response of some patients to therapy appeared to contribute to a weakening in all these relationships. This was partially corrected by allowing for variations in TBV in calculating the remaining regressions. Osteoclast numbers correlated well with both accretion and resorption rates but not with calcium balance. Only a minor part of the scatter associated with these statistical associations could be accounted for by methodological uncertainties; nevertheless in this homogeneous group of patients fair predictions of kinetic indices could be made from histomorphometric data and vice versa. The remainder of the scatter is likely to be due to variations in turnover between different sites in the skeleton, particularly between cortical and trabecular bone; and to the tendency of kinetic parameters to include a variable contribution from exchange processes which can only be corrected by more sophisticated techniques for measuring the formation rate of new bone with radioisotopes.

Secretion by glucagonomas of a possible glucagon precursor.

Five patients with glucagonomas had elevated plasma levels of total glucagon immunoreactivity. Gel filtrations of these plasma samples on Bio-Gel P30 columns showed that most of the immunoreactivity eluted in the 3,500-(true glucagon) and 9,000-dalton fractions. After the administration of alpha cell effectors, changes in total glucagon immunoreactivity were seen which were accounted for primarily by the 3,500-dalton species, but there were also changes in the 9,000-dalton moiety. Venous effluent plasma from tumors of two subjects contained elevated concentrations of glucagon immunoreactivity in both fractions. When material from both the 3,500- and 9,000-dalton peaks were serially diluted in a glucagon immunoassay, parallel displacement curves were found, suggesting that both have similar or identical antigenic determinants. Thus, with conversion to a neoplastic state, alpha cells of glucagonomas, much like beta cells of insulinomas, may secrete an increased amount of a larger, 9,000-mol wt glucagon species which may be a prohormone.

Activation and inhibition of mast cells degranulation affect their morphometric parameters

Activation of mast cells, the key cells of allergic inflammation, causes typical morphological changes associated with an increase in volume, that is a function of area and perimeter. The purpose of this study was to evaluate the effect of mast cell activation to degranulate, carried out by the secretagogue Compound 48/80, and of inhibition of this activation carried out by Nedocromil sodium, a mast cell stabilizing drug, on mast cell area, perimeter and shape factor by a computerized image analyzer. Mast cells were isolated and purified by peritoneal lavage of rats (purity >98%) and co-cultured with mouse 3T3 fibroblasts to which they adhere. Cultures were incubated for 10 min at 37 degrees C with culture medium alone (Enriched Medium) or Enriched Medium containing either Nedocromil (10(-4) M) or Compound 48/80 (0.3 microg/ml) or Compound 48/80 and Nedocromil (0.3 microg/ml and 10(-4) M respectively). Supernatants were then assessed for histamine release, as a marker of mast cell activation and the cell monolayers were fixed and stained with an alcoholic-acidic toluidine blue solution and examined with a computerized image analyzer connected with a light microscope. Mast cells incubated in Enriched Medium or Nedocromil possessed similar morphometric parameters. Mast cells activated with Compound 48/80 (70% histamine release) had a significant increase in area and perimeter and a decrease in shape factor in comparison to mast cells in Enriched Medium alone. Simultaneous incubation of mast cells with Compound 48/80 and Nedocromil significantly inhibited their histamine release (36% histamine release) and the increase in area and perimeter, but did not affect significantly their shape factor, in comparison with mast cells incubated with Compound 48/80 alone. These data clearly show that there is a relationship between mast cell activation, consequent histamine release and changes in cell area, perimeter and shape factor and that Nedocromil not only inhibits mast cell histamine release but also the activation induced morphometric changes in mast cells.

Autoimmune Hypocalciuric Hypercalcemia Unresponsive to Glucocorticoid Therapy in a Patient with Blocking Autoantibodies against the Calcium-Sensing Receptor

CONTEXT Autoantibodies directed against the calcium-sensing receptor (CaSR) have been reported in several individuals with various autoimmune disorders and PTH-mediated hypercalcemia. Previously, glucocorticoid treatment has been shown to decrease the CaSR autoantibody titers and normalize the hypercalcemia in a patient with autoimmune hypocalciuric hypercalcemia (AHH). OBJECTIVE The objective of the study was to evaluate a patient with AHH for the presence of blocking autoantibodies against the CaSR and to monitor her biochemical and serological responses to a trial of glucocorticoid therapy. RESULTS Glucocorticoid treatment had no effect on serum total or ionized calcium concentration or serum PTH levels, all of which remained at higher than normal levels. In contrast, on prednisone, urinary calcium excretion increased from overtly hypocalciuric levels to normal values. Anti-CaSR autoantibodies were detected at similar levels in the patients serum before, during, and after glucocorticoid treatment. Functional testing of these antibodies showed that they inhibited the stimulatory effect of extracellular Ca(2+) on ERK1/2 but did not suppress the calcium-induced accumulation of inositol-1-phosphate. CONCLUSIONS We report a patient with AHH with frankly elevated PTH levels who was found to have autoantibodies against the CaSR. The hypercalcemia and CaSR autoantibody titers failed to respond to glucocorticoid therapy, unlike a previously reported patient with similar clinical and biochemical features. The anti-CaSR antibody-mediated inhibition of CaSR-stimulated ERK1/2 activity, but not of inositol-1-phosphate accumulation, suggests that ERK1/2 may mediate, at least in part, the regulation of PTH secretion and urinary calcium excretion by the CaSR.