Parathyroid-like hormone

McAuley and colleagues evaluated a patient with malignant mesothelioma who had hypercalcemia and an elevated serum concentration of parathyroid-like hormone. They evaluated 9 epithelial mesotheliomas... 

Yamaguchi, M. and Kishi, S. (1995b). Inhibitory effect of zinc-chelating dipeptide on parathyroid hormone-stimulated osteoclast-like cell formation in mouse marrow cultures Involvement of calcium signalling. Peptides 16, 629-633. 

Vaes, G. Parathyroid hormone-like action of N6-2 -0-di-butyryladenosine 3 ,5 (cyclic)-monophosphate on hone explants in tissue culture. Nature 219, 939 (1968)... 

Herrmann-Erlee, M. P. M. A parathyroid hormone-like action of dibutyryl cyclic adenosine-3 ,5 monophosphate on the explanted embryonic mouse radius. Calc. Tiss. Res. 4, (Suppl.) 70 (1970)... 

Alendronate significantly reduced the anabolic effect of parathyroid hormone when the two were used in combination, both in postmenopausal women (22) and in men (23). It seems likely that this interaction will also apply to other bisphosphonates, although the mechanism has not been determined. 

The receptor for l,25(OH)2D exists in a wide variety of tissues—not just bone, gut, and kidney. In these "nonclassic" tissues, l,25(OH)2D exerts a number of actions including regulation of parathyroid hormone secretion from the parathyroid gland, insulin secretion from the pancreas, cytokine production by macrophages and T cells, and proliferation and differentiation of a large number of cells, including cancer cells. Thus, the clinical utility of l,25(OH)2D analogs is likely to expand. 

Soma S, Matsumoto S,Takano-Yamamoto T. Enhancement by conditioned medium of stretched calvarial bone cells of the osteoclast-like cell formation induced by parathyroid hormone in mouse bone marrow cultures. Archs Oral Biol. 1996 42(3) 205-211. 

The active metabolite of vitamin D, calcitriol, is formed in the proximal tubules of the kidneys from calcidiol. There are three cytochrome P450-dependent enzymes in kidneys that catalyze 1-hydroxylation of calcidiol CYP27A and CYP27 in mitochondria and a microsomal la-hydroxylase, which is ferredoxin-dependent. It is likely that the microsomal enzyme is the most important its synthesis is induced by cAMP in response to parathyroid hormone (Section 3.2.8.2) and repressed by calcitriol (Omdahl et al., 2001 Wikvall, 2001). 

The nuclear vitamin D receptor was originally studied in intestinal mucosa, hut has subsequently been found in a variety of other tissues that have therefore been shown to be vitamin D-responsive, including kidneys, bone, parathyroid gland, -islet cells of the pancreas, pituitary, placenta, uterus, mammary glands, skin, thymus, monocytes, macrophages, and activated T lymphocytes. Like other steroid hormone receptors, it is a zinc finger protein it has the same high affinity (of the order of 10 " M) for both calcitriol and ercalcitriol. 

Renal failure is associated with an osteomalacia-like syndrome, renal osteodystrophy, as a result of the loss of calcidiol 1-hydroxylase activity. The condition may be complicated by defective reabsorption of calcium and phosphate from the urine. Furthermore, the half-life of parathyroid hormone is increased, because the principal site of its catabolism is the kidney, so there is increased parathyroid hormone-stimulated osteoclastic action without the compensatory action of calcitriol (Mawer etal., 1973). 

Peak BMD is generally achieved in a woman s mid-thirties and then gradually declines, with 30% of bone loss occurring after menopause in the absence of HRT. A BMD T score of -1 or higher is considered normal. A score of -1 to -2.5 indicates osteopenia, and a score of -2.5 or lower indicates osteoporosis. Therefore, ED has osteopenia. ED s previous chronic use of steroids is likely to have contributed to her reduced BMD. Steroids increase renal calcium excretion and bone resorption by parathyroid hormone. They also decrease bone collagen synthesis. 

Peptide-hormones like hypothalamus-pituitary, gastrointestinal, parathyroid, neurohormones, Gfs related peptide-hormones cannot penetrate the plasma membrane and their receptors are located on the cell surface and the signal transport to the nucleus is becoming via a second messenger. The main hormone action seems to be DNA synthesis whereas other including mediation of neurotransmission, enzyme synthesis, regulation and synthesis of structural proteins are responsible for the specific characteristics of differentiated cell. 

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