Calcitonin

Comparison of low-dose intramuscular and intravenous salcatonin in the treatment of primary hyperparathyroidism

The treatment of hypercalcaemia with low-dose salcatonin (100 U/d), administered either as a single intramuscular bolus or as a continuous intravenous infusion for five days, was examined in two groups of 10 patients with primary hyperparathyroidism, in a randomized open parallel study. Both the peak (0.31 +/- 0.035 mmol/L v 0.13 +/- 0.034 mmol/L) and overall (0.073 +/- 0.016 mmol/L v 0.018 +/- 0.016 mmol/L) hypocalcaemic responses were greater in the infusion group. The peak reduction in serum calcium occurred on day 2 of treatment after which there was a progressive attenuation of response. All the differences between the two methods of administration wer due to renal rather than bony effects of salcatonin. Possible causes of progressive resistance to treatment included reductions in sodium excretion and serum phosphate. It is concluded that low-dose salcatonin administered as a continuous infusion was more effective than the same dose given as a bolus. The kidney played a pivotal role both in the cause of the hypercalcaemia and in the response to treatment, including the rapid development of resistance which limits the use of salmon calcitonin in primary hyperparathyroidism to short-term reduction of serum calcium.

The role of neuropeptides in cardiovascular regulation

During the past few years more than 30 novel, biologically active peptides have been discovered. Some are produced in endocrine glands and circulate as hormones in the blood; others are contained in the enterochromaffin cells of the gut and may be involved in the regulation of intestinal functions. The vast majority of new peptides, however, have been detected in the central and peripheral nervous systems, where they are synthesized in distinct neurons and stored in neurovesicles. Many of these neuropeptides may be involved in circulatory regulation. There is evidence supporting such a role, especially for centrally located angiotensin, opioid peptides, substance P, neuropeptide Y (NPY), vasopressin, atrial natriuretic peptide (ANP), kinins, corticotropin releasing factor, bombesin, and somatostatin. In this review we discuss the cardiovascular actions of angiotensin, neuropeptide Y, and calcitonin gene related peptide.

Recent advances in calcium metabolism. I. Mechanisms of calcium homeostasis

Within recent years newly acquired knowledge has provided a clearer understanding of some aspects of the complex mechanisms that collectively maintain calcium homeostasis within body fluids and it is our intent to define current concepts of the interrelationship of these various factors to the end that fuller understanding may be available concerning the maintenance of calcuim homeostasis in health as well as features which result in its disruption and the consequent effects of imbalances of calcium in various disease states. In this first section dealing with the physiologic state, there are included descriptions of: (1) the metabolism of vitamin D, the synthesis of its active metabolites, 25 OHD3 and1.25(OH)2D3, and the metabolic actions of the active vitamin D metabolite and analogues upon gastrointestinal, bone, and kidney functions; (2) the synthesis, secretion, and metabolic activity of parathyroid hormone and the difficulties with the radioimmunoassay of PTH related to the number of PTH-like peptides in the circulation; and (3) the chemistry, metabolism, and biologic activities of calcitonin, a hypocalcemic principle derived from the parafollicular cells of the thyroid gland. It is emphasized that under normal circumstances these humoral mechanisms act in an integrated manner to maintain serum concentrations of total and ionized calcium within narrowly defined limits.

The oxyphil and C cells of the human thyroid gland. A cytochemical and histopathologic review

The C and oxyphil cells of the human thyroid are analyzed in the light of recent advances in cellular biology, cytochemistry, and histopathology. The C cell is present in the normal human thyroid, where its identification is cardinally by means of argyrophilic cytoplasmic granules. The morphology, topography and argyrophilia of C cells are discussed with reference to tumor, cyst, and teratoma formation in the thyroid gland. Oxyphil cells of the thyroid are cytochemically akin to C cells but arise from follicular cells. They occur in the thyroid and other protein-producing organs, but are themselves inefficient producers of proteins and glycoproteins. Speculation is made on their morphological characteristics, and consideration is given to DNA-RNA involvement in the functional and morphological alterations of this follicular cell type.