Jacqueline G. Parthemore

New biochemical marker for bone metabolism. Measurement by radioimmunoassay of bone GLA protein in the plasma of normal subjects and patients with bone disease.

gamma-Carboxyglutamic acid-containing protein of bone (BGP) is an abundant noncollagenous protein of mammalian bone. BGP has a molecular weight of 5,800 and contains three residues of the vitamin K-dependent amino acid, gamma-carboxyglutamic acid. We have applied a radioimmunoassay based on calf BGP for the measurement of the protein in the plasma of 109 normal humans and 112 patients with various bone diseases. BGP in human plasma was demonstrated to be indistinguishable from calf BGP by assay dilution studies and gel permeation chromatography. The mean (+/- SE) concentration of BGP in normal subjects was 6.78 (+/- 0.20) ng/ml, 7.89 (+/- 0.32) for males and 4.85 (+/- 0.35) for females. Plasma BGP was increased in patients with Pagets disease of bone, bone metastases, primary hyperparathyroidism, renal osteodystrophy, and osteopenia. Plasma BGP did correlate with plasma alkaline phosphatase (AP) in some instances, but there were dissociations between the two. It was additionally observed that patients with liver disease had normal plasma BGP despite increased plasma AP, a reflection of the lack of specificity of AP measurements for bone disease. Our studies indicate that the radioimmunoassay of plasma BGP can be a useful and specific procedure for evaluating the patient with bone disease.

Changes in plasma bone GLA protein during treatment of bone disease.

SummaryBone Gla protein (BGP) was measured in the plasma by radioimmunoassay (RIA) during treatment of 59 patients with bone diseases including Pagets disease (N=9), primary hyperparathyroidism (N=25), chronic renal failure (N=20), and cancer involving bone (N=5). Plasma BGP was increased above normal in all patients. BGP decreased in the patients with Pagets disease following the acute and chronic administration of salmon calcitonin. Plasma BGP was higher in women then in men with primary hyperparathyroidism. Following parathyroidectomy, BGP decreased in both sexes but the decrease was significant in women only. Plasma BGP was increased in patients with renal osteodystrophy and did not change after hemodialysis. In the patients with bone cancer, plasma BGP decreased during treatment of the attendant hypercalcemia with salmon calcitonin. Although plasma BGP and serum alkaline phosphatase (AP) levels were generally correlated in these studies, there were examples of dissociation between the two. The measurement of plasma BGP appears to provide a specific index of bone metabolism that may in some circumstances be more sensitive than serum alkaline phosphatase measurement. However, further studies are necessary to establish the clinical value of plasma BGP measurement by RIA in the management of patients with bone diseases.

Immunoreactive calcitonin in the intermediate lobe of the pituitary gland

Abstract Immunoreactive-calcitonin was observed in all cells of the intermediate lobe of the rat pituitary gland. It may thus be a fragment of the ≥31, 000 daltons precursor molecule of adrenocorticotropin and β-lipotropin.

Hypercalcemia in Disseminated Coccidioidomycosis

Infectious diseases are seldom considered in the differential diagnosis of hypercalcemia.1 , 2 Bacterial, and perhaps viral, infections have only rarely been associated with an elevated blood calci...

Secretion of Calcitonin in Hypocalcemic States in Man

The control of calcitonin secretion in humans has been studied extensively only in patients with medullary thyroid carcinoma since the peripheral concentration of the hormone in normal subjects is too low for accurate measurement by existing assay procedures. However, we have recently found that the concentrations of calcitonin in the peripheral plasma of hypocalcemic subjects during provocative tests of hormone secretion were high enough to be measured by radioimmunoassay. Accordingly, the effect of calcium and pentagastrin infusions on plasma calcitonin was studied in nine patients with pseudohypoparathyroidism, seven patients with idiopathic hypoparathyroidism, and six patients with hypocalcemia not due to parathyroid disease. The infusion of calcium in these hypocalcemic subjects resulted in increases in plasma calcitonin to levels that could be readily detected by our radioimmunoassay. Pentagastrin infusion also caused an increase of plasma calcitonin in some subjects, but calcium was approximately 10 times more effective than gastrin in its stimulatory effect on hormone secretion. These results demonstrate that in humans as well as other mammals the secretion of calcitonin by parafollicular cells that are not involved by medullary thyroid carcinoma is directly related to plasma calcium and that gastrin can also stimulate hormone secretion. The results are consistent with the thesis that the secretion of calcitonin by normal human subjects does occur but at peripheral concentrations of the hormone below the detection limits of most existing immunoassays; hypocalcemia leads to increased stores of hormone that can be related by the appropriate stimuli.

Secretion of Parathyroid Hormone in Patients with Medullary Thyroid Carcinoma

The secretion of parathyroid hormone (PTH) and calcitonin (CT) was studied in 30 patients with medullary thyroid carcinoma. Most patients with elevated levels of CT were normocalcemic and also had normal basal levels of PTH. Five of six patients with associated hyperparathyroidism were hypercalcemic and had elevated basal PTH levels. Hormone secretion was also studied during infusions with standard and low doses of calcium. PTH unexpectedly increased during 12 of 18 calcium infusions. Such a paradoxical increase in PTH was seen in those patients with the greatest increase in CT and the least increase in calcium during the calcium infusion. Accordingly, increases in PTH concentration during the calcium infusions could be correlated directly with increases in CT and correlated inversely with increases in calcium. These observations suggest that, in some patients with medullary thyroid carcinoma, a further increase in the abnormally elevated CT levels may stimulate PTH secretion. Therefore, at least in acute studies, there may be a functional, as well as a genetic, relationship between the secretion of these two hormones in patients with this thyroid tumor.

Calcitonin secretion in congenital nongoitrous cretinism.

Plasma calcitonin (CT) was measured in the basal state and/or during provocative tests of hormone secretion in 11 children with congenital non-goitrous cretinism (CNC), in 1 girl with a lingual thyroid, and in 11 normal children. Basal and stimulated CT concentrations were significantly lower in the patients with CNC than in the normal subjects. Mean basal CT (+/- SE) was 41 +/- 4 pg/ml in the normal children, 24 +/- 3 pg/ml in the children with CNC, and 20 +/- 2 pg/ml in the patient with the lingual thyroid. The mean incremental CT responses to calcium infusion were 7.0 +/- 2 pg/ml in the children with CNC, 6.0 pg/ml in the patient with the lingual thyroid, and 146 +/- 47 pg/ml in the normal children. The children with CNC also demonstrated a significant delay in the return of the total serum calcium to basal level after the calcium infusion. The mean incremental CT response after infusion of pentagastrin was 7.6 +/- 2 pg/ml in the children with CNC, 10.0 pg/ml in the child with the lingual thyroid, and 34.4 +/- 11 pg/ml in the normal children. These data indicate that CT deficiency is present in children with CNC and suggest that the deficiency is a consequence of the defective embryologic development of the thyroid gland.

The regulation of calcitonin in normal human plasma as assessed by immunoprecipitation and immunoextraction.

We have studied the secretion of calcitonin in normal adults with a new procedure of increased sensitivity for the measurement of the hormone in peripheral plasma. In this method, endogenous calcitonin is immunoprecipitated with specific antibodies from a 10-ml plasma sample. The calcitonin is then dissociated from the antibodies and extracted into alcohol. The alcohol is evaporated, and the calcitonin is recovered in assay diluent for subsequent radioimmunoassay. The procedure produces a fivefold increase in immunoassay sensitivity and eliminates plasma proteins which can produce spurious immunoassay effects. This procedure was used to measure calcitonin in normal adults. The mean (+/- SE) plasma calcitonin in 43 subjects was 10 (+/- 2) pg/ml. A+ the end of a 3-h calcium infusion (12 mg/kg), mean plasma calcitonin in 10 subjects had risen to 114 (+/- 21) pg/ml. In 11 subjects, a 10-min infusion of 150 mg of calcium caused calcitonin to rise to a mean concentration of 28 (+/- 7) pg/ml at 20 min. EDTA infusion (50 mg/kg 2 h) caused a slight decrease in plasma calcitonin. These results are consistent with our previous reports of the low concentrations of calcitonin in adult plasma. Our data may underestimate calcitonin levels since not all of the heterogenous species of hormone may be extracted by this method. In any case, this procedure has allowed us to determine that the low concentrations of plasma calcitonin in normal adults are responsive to perturbations of calcium homeostasis. The immunoextraction method may be applicable to other assays in which it is necessary to increase sensitivity or define specificity.

Calcitonin secretion in renal disease.

Disorders of secretion and metabolism of parathyroid hormone (PTH) and vitamin D play an important role in the pathogenesis of the complex abnormalities of calcium and skeletal metabolism present in renal failure. In addition to these two calcium-regulating hormones, it has recently been observed that ealeitonin abnormalities are also found in renal failure. Elevated plasma levels of the hormone have been reported in renal disease by several investigators [3, 5]. We have applied our radioimmunoassay for calcitonin (CT) to a study of peripheral plasma calcitonin in renal failure [6].

286 STUDIES OF PLASMA CALCITONIN IN HYPOITUITARISM AND HYPOTHYROIDISM

The secretion of calcitonin (CT) was studied in 17 children, 10 with hypopituitarism and 7 with agoitrous hypothyroidism. Plasma CT levels were measured by radioimmunoassay in the basal state and following infusion of pentagastrin (0.5 μg/kg) and 10 minute infusions of calcium (2.3 mg/kg Ca++ as CaCl2). Of the 10 children who have hypopituitarism, 5 were studied before and after one year of human growth hormone (HGH) therapy and 5 were studied before treatment only. Basal and peak response CT levels were essentially unchanged by HGH. In the patients with hypopituitarism, CT levels increased from 41.9 ± 5.1 pg/ml to a peak of 67.4 ± 10 pg/ml after pentagastrin and from 38.8 ± 5.2 pg/ml to a peak of 107 ± 14.9 pg/ml after calcium infusion. In the cretins, CT levels increased from 33.8 ± 6.5 pg/ml to 35.8 ± 7 pg/ml following pentagastrin and from 31.4 ± 5.9 pg/ml to 40 ± 4.9 pg/ml following calcium. Although basal levels of CT seemed to be lower in cretins, these values could not be rigorously validated. The patients with hypopituitarism had greater CT responses than the cretins, especially to calcium infusion. These studies suggest that children with hypopituitarism have a greater CT response to calcium infusion than do normal adults and that CT secretion is abnormal in patients with athyreotic cretinism.