M. A. Dambacher

Differential effects of aging and disease on trabecular and compact bone density of the radius

We constructed a special purpose CT system to get a spatial resolution of 0.2 mm and developed a procedure for the precise determination of trabecular and compact bone density (TBD and CBD) in the radius. Seven groups of healthy females and patients were measured to explore differential effects on compact and trabecular bone. In healthy females CBD remains constant within 0.2% from age 20 to 70. TBD measured in the same individuals is reduced by 50%. The scatter of the individual CBD values is 1.5% only, that of TBD 20%. Longitudinal examinations of corticosteroid treated asthmatics during one year showed a loss of TBD of 4.8%. During the same period CBD remained completely stable. In other diseases such as hyperparathyroidism CBD is reduced as well. This study showed the feasibility of a noninvasive determination of the density of compact bone and demonstrated that density loss of compact and trabecular bone is considerably different.

Localization of regional forearm bone loss from high resolution computed tomographic images.

The precise site of bone loss was evaluated in early postmenopausal women using high resolution computed tomographic (CT) images of forearm measurements. A procedure was devised to quantitate trabecular and subcortical bone density of the distal radius, cortical bone density of the diaphyseal radius, and cortical wall thickness at both measuring sites. Twenty women (mean age 52 years, time since menopause 1 to 4 years) were examined twice at one-year intervals to determine the yearly change of the above mentioned bone parameters. Trabecular bone and subcortical bone showed the same density reduction of 7 mg/cm3 per year. Cortical bone density remains unchanged and no increase in porosity can be seen. For early postmenopausal women the reduction of bone mass (BMC) in the diaphysis of the radius is, therefore, due to a thinning of the cortical wall. This is in accordance with the observed average loss of wall thickness of 0.04 mm per year. The non-invasive determination of the precise localization of bone changes in individual patients should be of value in the assessment of the severity of osteoporosis. Furthermore it has potential in the evaluation of the efficacy of therapeutic procedures in the various disease states.

Formation of neutralizing antibodies during intranasal synthetic salmon calcitonin treatment of postmenopausal osteoporosis

Nineteen patients with postmenopausal osteoporosis were treated with 200 u (15 nmol) synthetic salmon calcitonin (sCT) intranasally per day for 15 months. Six months after the start of the nasal administration of sCT, antibodies were recognized in 7, and after 15 months in 10 of the 19 patients studied. The half-maximal dilution of serum binding to 60 pmol/1 [125I] sCT (dilution-50) ranged from 2 to 490, and half-maximal inhibition of [125I]sCT binding (60 pmol/1) from 91 to 221 pmol/l sCT. In a cultured breast cancer cell line (T47D) cAMP production was stimulated by sCT (EC50 70 pmol/l). Stimulated cAMP production by sCT (50 pmol/1) was reduced to between 4% and 23% in the presence of serum from patients with antibody dilution-50 of [125I]sCT binding exceeding 32. In patients with lower titer antibodies cAMP production was only marginally suppressed. The values of patients with postmenopausal osteoporosis were in the range of those of earlier studied patients with Pagets disease and clinical resistance to sCT. There was a linear relation between the antibody dilution-50 and the serum dilution required for half-maximal inhibition of cAMP production (P<0.01). In conclusion, neutralizing antibodies to sCT may contribute to the decreased responsiveness of bone mineral loss during prolonged treatment with sCT.

Comparison of the treatment effects of ossein-hydroxyapatite compound and calcium carbonate in osteoporotic females.

The aim of the study was to evaluate whether ossein-hydroxyapatite (OHC) is more effective than calcium carbonate (CC) in preventing futher bone loss in postmenopausal osteoporosis. Forty osteoporotic patients were monitored for 20 months. The patients were randomly assigned to one of two groups and treated in a double-masked manner with 1400 mg calcium per day, in the form of either OHC or CC. OHC consists of hydroxyapatite, collagens and non-collagenous proteins/peptides containing insulin-like growth factor I (IGF-I; 1341 ng), insulin-like growth factor II (IGF-II; 670 ng), transforming growth factor beta (TFG-β; 166 ng) and osteocalcin (47 µg). The bone densities were evaluated at intervals of 4 months with high-precision peripheral quantitative computed tomography. After 20 months of treatment the loss of trabecular bone was 0.8±0.5% in the OHC group and 1.8±0.7% in the CC group. The difference between the OHC and CC groups was statistically significant. This study shows that OHC is more effective than CC in slowing peripheral trabecular bone loss in patients with manifest osteoporosis.

Efficacy of intranasal human calcitonin in patients with Paget's disease refractory to salmon calcitonin☆

PURPOSE A cause for the resistance to intranasal salmon calcitonin (sCT) therapy in patients with Pagets disease is the occurrence of neutralizing antibodies to sCT. As a result, a new formulation of intranasal human calcitonin (hCT) was developed, and the efficacy investigated in patients treated earlier with sCT. PATIENTS AND METHODS Twelve patients with Pagets disease were treated twice daily for 6 months with 1 mg synthetic hCT administered intranasally. Five patients demonstrated low-titer antibodies to sCT, and four of the patients did not respond previously to 1-year therapy with intranasal sCT. The hypocalcemic effect of 3 mg hCT was compared to that of 0.1 mg sCT before and after the intranasal hCT therapy. Serum alkaline phosphatase and the ratio between the urinary excretion of hydroxyproline and creatinine were measured before and during intranasal hCT treatment. RESULTS The hypocalcemic response to 3 mg intranasal hCT (-6.60 +/- 0.67%, mean +/- standard error) was similar before and at the end of intranasal hCT therapy (-5.92 +/- 0.80%, p greater than 0.1). Intranasal sCT (0.1 mg) lowered serum calcium less effectively (-2.86 +/- 0.76%) than 3 mg intranasal hCT (p less than 0.05). The presence of low-titer antibodies to sCT did not affect the hypocalcemic response to sCT or hCT. As a result of the 6-month intranasal hCT regimen, serum alkaline phosphatase and urinary hydroxyproline/creatinine ratio were reduced to 62 +/- 5% (p less than 0.001) and 80 +/- 7% (p less than 0.05) respectively, of pretreatment levels. In four patients previously resistant to intranasal sCT therapy because of neutralizing antibodies to sCT, serum alkaline phosphatase was similarly lowered by intranasal hCT to 66 +/- 6% of pretreatment levels (p less than 0.05). CONCLUSION A new formulation of intranasal hCT effectively lowered serum calcium levels, alkaline phosphatase concentrations, and urinary hydroxyproline excretion in patients with Pagets disease, some of whom were previously resistant to intranasal sCT because of neutralizing antibodies.

Salmon and human calcitonin-like peptides in man.

Calcitonin‐like peptides have been identified in the serum of normal subjects and of medullary thyroid carcinoma (MTC) patients. Using specific homologous radioimmunoassays (RIA) in combination with reversed‐phase high performance liquid chromatography and gel permeation chromatography under denaturing conditions, we have recognized major components which coeluted with human calcitonin‐(1–32), PDN‐21, a carboxyl‐terminal flanking peptide derived from the calcitonin mRNA sequence, and salmon calcitonin‐(1–32). An additional 12000 molecular weight peak possibly represents a human calcitonin‐PDN‐21 polyprotein. In both the human calcitonin‐(1–32) (normal value < 0·043 ngEq/ml; MTC 140·80 ngEq/ml, mean value±SEM) and the PDN‐21 (normal value <0·050 ngEq/ml; MTC 33·6±16·5 ngEq/ml) RIAs, serum levels were increased in MTC patients. Circulating levels of the salmon calcitonin‐like peptide were indistiguishable between normal subjects (0·038 ± 0·006 ngEq/ml) and MTC patients (0·037 ± 0·011 ngEq/ml).

Regulation of parathyroid hormone secretion in vitro and in vivo

Although the inverse relationship between extracellular calcium (and magnesium) levels and parathyroid hormone (PTH) responses is clearly established, much remains to be learned about the mechanism of the calcium-regulated PTH release and the role of factors other than calcium on the secretion of the hormone. The biosynthesis and release of PTH have been extensively studied in vitro with so-called static systems. Parathyroid tissue is incubated in media with different regulators, and medium samples are taken after time periods ranging from 10 rain to several hours. The minute-tominute regulation of PTH secretion can best be studied in vitro with a perifusion system [1]. The control of F r H secretion in vivo can, strictly speaking, be investigated only in the venous parathyroid effluent of parathyroid glands [2, 3], since measurements in peripheral blood represent the balance between secretion and metabolism of the hormone. In theory, use of the venous parathyroid effluent is the most suitable method for studying PTH secretion. In practice, at least in our hands, it has been impossible to obtain reproducible results even from parathyroid tissue transplanted into the forearm, since parathryoid veins are too small to be reliably cannulated. Moreover, not only the secretion of PTH-(1-84) but also its metabolism is calcium regulated [1, 3-5]. In the present review, rather than focusing on various potential regulators of PTH secretion, we want to concentrate on some methodological and conceptual problems concerning the control of PTH release.

PARATHYROID SUPPRESSIBILITY IN HYPERPARATHYROIDISM DUE TO CHRONIC RENAL FAILURE: STUDIES WITH AUTOTRANSPLANTED PARATHYROID TISSUE

Suppressibility of parathyroid hormone (PTH) secretion by calcium was evaluated in six patients with chronic renal failure and parathyroid tissue autotransplanted into the forearm. One patient was reinvestigated after renal transplantation. Plasma PTH levels were measured in the venous effluent of transplanted parathyroid tissue (VE) and in peripheral blood (PB) with two radioimmunoassays (RIA). One of these detected predominantly the intact human parathyroid hormone‐(1–84) [PTH‐(1–84)] (N‐assay) and another in addition carboxyl (COOH)‐terminal fragments (C‐assay). At 5 min after the start of 12‐min calcium infusions, resulting in a mean increase of plasma calcium levels of 0±6 mmol/l (P < 0±01), PTH was lowered to 44±10% (mean ± SE) (P < 0±01) of preinfusion levels in the VE and to 88±4% (P < 0±05) in PB, when measured in the N‐assay; subsequently the plasma calcium level remained raised and PTH level lowered. When estimated in the C‐assay, PTH was significantly lowered to 82± 6% (P < 0–05) in the VE at 120 min, and to between 91 ± 2% and 96 ± 2% (P < 0±01‐ < 0±05) in the PB at 20 to 120 min after the start of the calcium infusions. The results were extended with gel permeation chromatography of representative plasma samples. After renal transplantation and restoration of renal function gel filtration analysis indicated that the levels of intact PTH‐(1–84) were 49±6 and of its COOH‐terminal fragments 3±5 higher in the VE than in PB. In response to i.v. calcium administration intact PTH and its COOH‐terminal fragments were lowered to 25% and 62% in the VE, and to 29% and 86% in PB, respectively. These findings demonstrate that the secretion of intact PTH‐(1–84) is suppressed within minutes in response to i.v. calcium administration; a slower fall of the secretion of COOH‐terminal PTH fragments was demonstrated only after restoration of near‐normal renal function.

Diagnosis and treatment of primary hyperparathyroidism

SummaryThe leading symptom of primary hyperparathyroidism is renal lithiasis which was present in 64 of 100 cases, whereas bone disease was noted in 11 per cent only. The diagnosis of primary hyperparathyroidism is generally made on the basis of raised serum levels of calcium and of immunoreactive parathyroid hormone (PTH). With antibodies detecting primarily COOH-terminal fragments of intact PTH-(1-84) there was an almost total discrimination of serum levels of PTH in normal subjects and in patients with primary hyperparathyroidism. Serum PTH was in the upper normal range in only 5 per cent of 128 patients with surgically verified hyperparathyroidism, whereas PTH was normal or undetectable in 35 hypercalcaemic patients with tumours unrelated to the parathyroid glands. A comparable discrimination of patients with primary hyperparathyroidism from normal subjects can be achieved with the measurement of the urinary cyclic adenosine 3′, 5′-monophosphate excretion, provided it is related to the glomerular filtration rate. With the measurement of the urinary excretion of calcium and phosphate, on the other hand, there is a large overlap in control subjects and in patients with primary hyperparathyroidism.The surgical removal of parathyroid tumours is the treatment of choice of primary hyperparathyroidism. In the routine preoperative evaluation, we do not recommend PTH measurements in the venous effluent of parathyroid tumours, since all parathyroid glands have to be surgically localized. In previously explored patients the interpretation of selective PTH measurements is difficult because of distorsion of the venous drainage from the parathyroid glands.

Parathyroid Hormone Secretory Responses to Peroral Phosphate and Stimulability of Serum Levels of Carboxyl-Terminal Flanking Peptide (PND-21) of the Human Calcitonin Gene by Calcium in Normal Subjects and Osteoporotic Patients

The roles of calciotropic hormones in the pathogenesis and treatment of osteoporosis are not clearly understood. Here we have assessed serum levels of immunoreactive parathyroid hormone (PTH) and urinary cyclic AMP excretion before and after acute peroral phosphate administration in osteoporotic patients and normal subjects of the same age. In some osteoporotic patients serum levels of PTH were measured after prolonged (5 days) treatment with peroral phosphate. Serum levels of immunoreactive carboxyl-terminal flanking peptide (PDN-21) (katacalcin is a synonym) of the human calcitonin gene which are closely related to calcitonin levels were also measured before and after iv calcium injections (1). The diagnosis of osteoporosis was established on the basis of at least one vertebral compression fracture. Control subjects had normal serum levels of calcium, phosphate and creatinine, and they presented no history of renal, hepatic and intestinal disease. None of the subjects were treated with glucocorticoids or were alcoholics.