http://www.medicine-encyclopedia.net Medical Encyclopedia en-US Fri, 17 Dec 2009 14:57:36 CEST Mon, 03 Feb 2009 01:21:00 CEST www.medicine-encyclopedia.net 60 http://www.medicine-encyclopedia.net/images/logo.gif http://www.medicine-encyclopedia.net 214 40 http://www.medicine-encyclopedia.net/sections-49-Genetic-Causes-of-Hypoparathyroidism.html http://www.www.medicine-encyclopedia.net/sections-49-Genetic-Causes-of-Hypoparathyroidism.html Hypoparathyroidism is characterized clinically by the presence of hypocalcemia and hyperphosphatemia due to inadequate supply or effectiveness of circulating parathyroid hormone (PTH). It may be present either as an isolated finding or as a component of a more complex developmental, metabolic, or endocrinologic syndrome.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-47-Molecular-Genetic-Abnormalities-in-Sporadic-Hyperparathyroidism-Part-I.html http://www.www.medicine-encyclopedia.net/sections-47-Molecular-Genetic-Abnormalities-in-Sporadic-Hyperparathyroidism-Part-I.html The biochemical state of primary hyperparathyroidism is generally caused by hypercellular parathyroid glands categorized as multigland hyperplasia, benign adenoma or malignant carcinoma. Most, and probably all, adenomas and carcinomas are monoclonal in origin, and specific clonal genetic lesions have been identified in most of these tumors.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-47-Molecular-Genetic-Abnormalities-in-Sporadic-Hyperparathyroidism-Part-II.html http://www.www.medicine-encyclopedia.net/sections-47-Molecular-Genetic-Abnormalities-in-Sporadic-Hyperparathyroidism-Part-II.html Tumor Suppressor Genes: MEN1 The Multiple Endocrine Neoplasia Type 1 Syndrome The multiple endocrine neoplasia type 1 (MEN1) syndrome, an autosomal dominant inherited disease, is characterized by multiple tumors of the parathyroids, enteropancreatic tissues and anterior pituitary.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-46-Molecular-Mechanisms-in-Parathyroid-Tumorigenesis.html http://www.www.medicine-encyclopedia.net/sections-46-Molecular-Mechanisms-in-Parathyroid-Tumorigenesis.html Primary hyperparathyroidism (1 HPT) is a relatively common disorder, with an estimated prevalence of 1:500-1:1000. In about 80%-85% of 1 HPT cases, a single enlarged parathyroid gland with a distinct capsule that separates the tumorous from the nontumorous tissue (=adenoma or uniglandular disease) is detected.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-44-Parathyroid-Gland-Hyperplasia-in-Renal-Failure-Part-I.html http://www.www.medicine-encyclopedia.net/sections-44-Parathyroid-Gland-Hyperplasia-in-Renal-Failure-Part-I.html Secondary hyperparathyroidism, a frequent complication of chronic renal failure, is characterized by parathyroid hyperplasia and enhanced synthesis and secretion of parathyroid hormone (PTH). High circulating PTH levels are not only a major contributor to osteitis fibrosa and bone loss, typical features of renal osteodystrophy.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-44-Parathyroid-Gland-Hyperplasia-in-Renal-Failure-Part-II.html http://www.www.medicine-encyclopedia.net/sections-44-Parathyroid-Gland-Hyperplasia-in-Renal-Failure-Part-II.html Vitamin D Regulation of Uremia- and High Phosphate-Induced Parathyroid Cell Growth Several laboratories have demonstrated a role for 1,25(OH)2D3 in suppressing parathyroid cell proliferation in vitro, and in vivo in uremia-induced PT hyperplasia in 5/6 nephrectomized rats.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-41-Regulation-of-Parathyroid-Hormone-Gene-Expression-by-Dihydroxyvitamin-D.html http://www.www.medicine-encyclopedia.net/sections-41-Regulation-of-Parathyroid-Hormone-Gene-Expression-by-Dihydroxyvitamin-D.html Vitamin D’s active metabolite 1,25(OH)2D3 acts on the parathyroid to markedly decrease PTH gene transcription. It does this by binding to its specific receptor in the parathyroid which then binds to a defined sequence, the vitamin D response element (VDRE) in the parathyroid hormone (PTH) gene promoter. Retinoic acid amplifies the effect of 1,25(OH)2D3 to decrease PTH mRNA levels suggesting that a VDR-RXR heterodimer binds to the VDRE.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-40-Regulation-of-Parathyroid-Hormone-mRNA-Stability-by-Calcium-and-Phosphate.html http://www.www.medicine-encyclopedia.net/sections-40-Regulation-of-Parathyroid-Hormone-mRNA-Stability-by-Calcium-and-Phosphate.html Abstract Calcium and phosphate regulate parathyroid hormone (PTH) secretion, gene expression and if prolonged also parathyroid proliferation. The regulation of PTH gene expression by Ca2+ and Pi is post-transcriptional, affecting mRNA stability.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-50-Skeletal-and-Reproductive-Abnormalities-in-Pth-Null-Mice.html http://www.www.medicine-encyclopedia.net/sections-50-Skeletal-and-Reproductive-Abnormalities-in-Pth-Null-Mice.html We have examined the role of parathyroid hormone (PTH) in the postnatal state in a mouse model of PTH-deficiency generated by targeting the Pth gene in ES cells. Mice homozygous for the ablated allele, when maintained on a normal calcium intake, developed hypocalcemia, hyperphosphatemia, and low circulating 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] levels consistent with primary hypoparathyroidism.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-39-The-Calcium-Sensing-Receptor.html http://www.www.medicine-encyclopedia.net/sections-39-The-Calcium-Sensing-Receptor.html Abstract The acute secretory response of parathyroid hormone (PTH) is strictly regulated by the extracellular calcium concentration (Ca2+ o), and the G protein-coupled, calcium-sensing receptor (CaR) located on the chief cells of the parathyroid glands mediates this process. Abnormalities of the Ca2+ o-sensing system lead to diseases that show hypo-/hypersecretion of PTH in addition to relative hyper-/hypocalciuria.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-38-Toward-an-Understanding-of-Human-Parathyroid-Hormone-Structure-and-Function.html http://www.www.medicine-encyclopedia.net/sections-38-Toward-an-Understanding-of-Human-Parathyroid-Hormone-Structure-and-Function.html PTH and Its Receptor Family Parathyroid hormone (PTH) is synthesized as a 115 amino acid precursor and secreted as an 84 amino acid polypeptide that regulates extracellular calcium homeostasis via actions directly on kidney and bone and indirectly on the intestine by facilitating calcium absorption.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-42-Vitamin-D-Analogs-for-the-Treatment-of-Secondary-Hyperparathyroidism-in-Chronic-Renal-Failure-Part-I.html http://www.www.medicine-encyclopedia.net/sections-42-Vitamin-D-Analogs-for-the-Treatment-of-Secondary-Hyperparathyroidism-in-Chronic-Renal-Failure-Part-I.html Secondary hyperparathyroidism (2oHPT) is a common complication in patients with chronic renal failure. The pathogenesis of 2oHPT is attributed primarily to phosphate retention and low serum 1,25(OH)2D3. Replacement therapy with calcitriol [1,25-dihydroxyvitamin D3 or 1,25(OH)2D3] or its precursor alfacalcidol [1a(OH)D3] often produces hypercalcemia, especially when combined with calcium-based phosphate binders.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/sections-42-Vitamin-D-Analogs-for-the-Treatment-of-Secondary-Hyperparathyroidism-in-Chronic-Renal-Failure-Part-II.html http://www.www.medicine-encyclopedia.net/sections-42-Vitamin-D-Analogs-for-the-Treatment-of-Secondary-Hyperparathyroidism-in-Chronic-Renal-Failure-Part-II.html Other Analogs The search for more effective vitamin D analogs for treating secondary hyperparathyroidism continues. Several have been tested in animal models. Fan et al compared 1,25-dihydroxy-dihydrotachysterol [1,25(OH)2DHT], 1,25(OH)2D3, and OCT for their abilities to suppress PTH in the uremic rat model. Five daily doses of 1 ng of 1,25(OH)2D3 caused significant hypercalcemia and a 50% decrease in PTH.... Mon, 03 Feb 2009 01:21:00 GMT http://www.medicine-encyclopedia.net/article-49-Parathyroid-Hormone-from-Gene-to-Protein-Part-II.html http://www.www.medicine-encyclopedia.net/article-48-Parathyroid-Hormone-from-Gene-to-Protein-Part-II.html Structure of the PTH mRNA The 5’ Untranslated Region The 5’ untranslated sequence of the longer forms of the human and bovine mRNAs and rat PTH mRNA contains about 120 nucleotides, and the shorter bovine and human cDNAs contain about 100 nucleotides in the 5’ noncoding region.... Sat, 25 Jan 2009 00:00:00 GMT http://www.medicine-encyclopedia.net/article-48-Parathyroid-Hormone-from-Gene-to-Protein-Part-I.html http://www.www.medicine-encyclopedia.net/article-48-Parathyroid-Hormone-from-Gene-to-Protein-Part-I.html The biosynthetic pathway of parathyroid hormone (PTH) has been studied from gene expression to PTH intracellular processing. The processing of PTH has been described and involves the synthesis of an initial translational product, preProPTH, and two proteolytic cleavages that in turn produce ProPTH and PTH.... Sat, 24 Jan 2009 00:00:00 GMT http://www.medicine-encyclopedia.net/article-47-Development-of-Parathyroid-Glands.html http://www.www.medicine-encyclopedia.net/article-47-Development-of-Parathyroid-Glands.html The parathyroid glands (PG) are the main source for circulating parathyroid hormone (PTH), a hormone that is essential for the regulation of calcium and phosphate metabolism. The PGs develop during embryogenesis from the pharyngeal pouches with contributions from endodermal and neural crest cells.... Sat, 23 Jan 2009 10:00:00 GMT http://www.medicine-encyclopedia.net/sections-25.html http://www.www.medicine-encyclopedia.net/sections-25.html The zinc topped tables used for many years to prepare tar “spreads” in a teaching hospital dermatology department were recently thrown out a sign of the times and an indication of both the increasing use of systemic treatment and much more effective forms of phototherapy.... Sat, 17 Jan 2009 15:30:20 GMT