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Concept: Hyperparathyroidism

167

BACKGROUND: Until now the exact biochemical processes during healing of metaphyseal fractures of healthy and osteoporotic bone remain unclear. Especially the physiological time courses of 25(OH)D3 (Vitamin D) as well as PTH (Parathyroid Hormone) the most important modulators of calcium and bone homeostasis are not yet examined sufficiently. The purpose of this study was to focus on the time course of these parameters during fracture healing. METHODS: In the presented study, we analyse the time course of 25(OH)D3 and PTH during fracture healing of low BMD level fractures versus normal BMD level fractures in a matched pair analysis. Between March 2007 and February 2009 30 patients older than 50 years of age who had suffered a metaphyseal fracture of the proximal humerus, the distal radius or the proximal femur were included in our study. Osteoporosis was verified by DEXA measuring. The time courses of 25(OH)D3 and PTH were examined over an eight week period. Friedmann test, the Wilcoxon signed rank test and the Mann-Withney U test were used as post-hoc tests. A p-value <= 0.05 was considered significant. RESULTS: Serum levels of 25(OH)D3 showed no differences in both groups. In the first phase of fracture healing PTH levels in the low BMD level group remained below those of the normal BMD group in absolute figures. Over all no significant differences between low BMD level bone and normal BMD level bone could be detected in our study. CONCLUSIONS: The time course of 25(OH)D3 and PTH during fracture healing of patients with normal and low bone mineral density were examined for the first time in humans in this setting and allowing molecular biological insights into fracture healing in metaphyseal bones on a molecural level. There were no significant differences between patients with normal and low BMD levels. Hence further studies will be necessary to obtain more detailed insight into fracture healing in order to provide reliable decision criteria for therapy and the monitoring of fracture healing.

Concepts: Osteoporosis, Bone, Vitamin D, Calcitonin, Bone fracture, Parathyroid hormone, Calcium, Hyperparathyroidism

165

Chronic renal failure (CRF) is associated with the development of secondary hyperparathyroidism and vascular calcifications. We evaluated the efficacy of PA21, a new iron-based non-calcium phosphate binder, in controlling phosphocalcic disorders and preventing vascular calcifications in uremic rats. Rats with adenine-diet-induced CRF were randomized to receive either PA21 0.5%, 1.5% or 5% or calcium carbonate (CaCO3) 3% in the diet, for 4 weeks and were compared with uremic and non-uremic control groups. After 4 weeks' phosphate binder treatment, serum calcium, creatinine and body weight were similar between all CRF groups. Serum phosphorus was reduced with CaCO3 3% (2.06 mmol/l, P≤0.001), PA21 1.5% (2.29 mmol/l, P<0.05) and PA21 5% (2.21 mmol/l, P≤0.001) versus CRF controls (2.91 mmol/l). Intact parathyroid hormone was strongly reduced in the PA21 5% and CaCO3 3% CRF groups to a similar extent (1138 and 1299 pg/ml, respectively) versus CRF controls (3261 pg/ml, both P≤0.001). A lower serum fibroblast growth factor 23 concentration was observed in the PA21 5%, compared with CaCO3 3% and CRF, control groups. PA21 5% CRF rats had a lower vascular calcification score compared with CaCO3 3% CRF rats and CRF controls. In conclusion, PA21 was as effective as CaCO3 at controlling phosphocalcic disorders but superior in preventing the development of vascular calcifications in uremic rats. Thus, PA21 represents a possible alternative to calcium-based phosphate binders in CRF patients.

Concepts: Renal failure, Nephrology, Carbon dioxide, Parathyroid hormone, Calcium carbonate, Hyperparathyroidism, Organ failure, Phosphate binders

148

Hypoparathyroidism is a disease of chronic hypocalcemia and hyperphosphatemia due to a deficiency of parathyroid hormone (PTH). PTH and analogs of the hormone are of interest as potential therapies. Accordingly, we examined the pharmacological properties of a long-acting PTH analog, [Ala(1,3,12,18,22) , Gln(10) ,Arg(11) ,Trp(14) ,Lys(26) ]-PTH(1-14)/PTHrP(15-36) (LA-PTH) in thyroparathyroidectomized (TPTX) rats, a model of HP, as well as in normal monkeys. In TPTX rats, a single intra-venous administration of LA-PTH at a dose of 0.9 nmol/kg increased serum calcium (sCa) and decreased serum phosphate (sPi) to near-normal levels for longer than 48 hours, while PTH(1-34) and PTH(1-84), each injected at a dose 80-fold higher than that used for LA-PTH, increased sCa and decreased sPi only modestly and transiently (< 6 hours). LA-PTH also exhibited enhanced and prolonged efficacy versus PTH(1-34) and PTH(1-84) for elevating sCa when administered subcutaneously (SC) into monkeys. Daily SC administration of LA-PTH (1.8 nmol/kg) into TPTX rats for 28-days elevated sCa to near normal levels without causing hypercalciuria or increasing bone resorption markers, a desirable goal in the treatment of hypoparathyroidism. The results are supportive of further study of long-acting PTH analogs as potential therapies for patients with hypoparathyroidism. This article is protected by copyright. All rights reserved.

Concepts: Bone, Parathyroid hormone, Bone resorption, Calcium metabolism, Parathyroid gland, Hypoparathyroidism, Hyperparathyroidism, Copyright

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Disorders of mineral metabolism, including secondary hyperparathyroidism, are thought to contribute to extraskeletal (including vascular) calcification among patients with chronic kidney disease. It has been hypothesized that treatment with the calcimimetic agent cinacalcet might reduce the risk of death or nonfatal cardiovascular events in such patients.

Concepts: Renal failure, Chronic kidney disease, Nephrology, Erythropoietin, Disease, Cardiovascular disease, Hyperparathyroidism, Cinacalcet

28

Osteoporosis affects more than 200 million people worldwide leading to more than 2 million fractures in the US alone. Unfortunately, surgical treatment is limited in patients with low bone mass. Parathyroid hormone (PTH) was shown to induce fracture repair in animals by activating mesenchymal stem cells (MSCs). However it would be less effective in patients with fewer and/or dysfunctional MSCs due to aging and comorbidities. To address this, we evaluated the efficacy of combination intravenous MSC and PTH therapy versus monotherapy and untreated controls, in a rat model of osteoporotic vertebral bone defects. The results demonstrated that combination therapy significantly increased new bone formation versus monotherapies and no treatment by 2 weeks (p<0.05). Mechanistically, we found that PTH significantly enhanced MSC migration to the lumbar region, where the MSCs differentiated into bone-forming cells. Finally, we used allogeneic porcine MSCs and observed similar findings in a clinically relevant minipig model of vertebral defects. Collectively, these results demonstrate that in addition to its anabolic effects, PTH functions as an adjuvant to intravenous MSC therapy by enhancing migration to heal bone loss. This systemic approach could be attractive for various fragility fractures, especially using allogeneic cells that do not require invasive tissue harvest.Molecular Therapy (2015); doi:10.1038/mt.2015.211.

Concepts: Osteoporosis, Bone, Vitamin D, Calcitonin, Mesenchymal stem cell, Bone marrow, Osteoclast, Hyperparathyroidism

28

Hungry bone syndrome refers to the rapid, profound and prolonged hypocalcaemia associated with hypophosphataemia and hypomagnesaemia and exacerbated by suppressed parathyroid hormone levels, which follows parathyroidectomy in patients with severe primary hyperparathyroidism and preoperative high bone turnover. It is a relatively uncommon, but serious adverse effect of parathyroidectomy. We conducted a literature search of all available studies reporting a “hungry bone syndrome” in patients who had a parathyroidectomy for primary hyperparathyroidism, to identify patients at risk and address the pitfalls in their management. The severe hypocalcaemia is believed to be due to increased influx of calcium into bone, due to the sudden removal of the effect of high circulating levels of PTH on osteoclastic resorption, leading to a decrease in the activation frequency of new remodelling sites and to a decrease in remodelling space, although there is no good documentation for this. Various risk factors have been suggested for the development of a hungry bone syndrome, including older age, weight/volume of the resected parathyroid glands, radiological evidence of bone disease and vitamin D deficiency. The syndrome is reported in 25-90% of patients with radiological evidence of hyperparathyroid bone disease versus only 0-6% of patients without skeletal involvement. There is insufficient data-based evidence on the best means to treat, minimize or prevent this severe complication of parathyroidectomy. Treatment is aimed at replenishing the severe calcium deficit by using high doses of calcium supplemented by high doses of active metabolites of vitamin D. Adequate correction of magnesium deficiency and normalization of bone turnover are required for resolution of the hypocalcaemia which may last for a number of months after successful surgery. Pre-operative treatment with bisphosphonates has been suggested to reduce postoperative hypocalcaemia, but there are to date no prospective studies addressing this issue.

Concepts: Osteoporosis, Bone, Vitamin D, Calcitonin, Parathyroid hormone, Parathyroid gland, Hypoparathyroidism, Hyperparathyroidism

28

The underlying molecular alterations causing sporadic parathyroid adenomas that drive primary hyperparathyroidism have not been thoroughly defined.

Concepts: Mutation, Parathyroid gland, Hyperparathyroidism, Parathyroid adenoma

27

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The treatment of primary hyperparathyroidism consists almost exclusively in the parathyroidectomy. The preoperative imaging (ultrasonography, 99mTc sestamibi scan) can allow to localize the pathologic gland and perform minimally-invasive focused techniques, but in presence of ectopic or intrathyroidal glands, parathyroid hyperplasia or coexistent thyroid disease, the sensitivity of these imaging techniques worsens. The present study shows a new technique of preoperative scintigraphic imaging and describes the early applications of this technique investigating if it is useful in improving the localization of the pathologic parathyroid.

Concepts: Medical imaging, Parathyroid hormone, Thyroid, Endocrine system, Parathyroid gland, Glands, Hypoparathyroidism, Hyperparathyroidism

21

Tertiary hyperparathyroidism is a common cause of hypercalcemia after kidney transplant. We designed this 12-month, prospective, multicenter, open-label, randomized study to evaluate whether subtotal parathyroidectomy is more effective than cinacalcet for controlling hypercalcemia caused by persistent hyperparathyroidism after kidney transplant. Kidney allograft recipients with hypercalcemia and elevated intact parathyroid hormone (iPTH) concentration were eligible if they had received a transplant ≥6 months before the study and had an eGFR>30 ml/min per 1.73 m(2). The primary end point was the proportion of patients with normocalcemia at 12 months. Secondary end points were serum iPTH concentration, serum phosphate concentration, bone mineral density, vascular calcification, renal function, patient and graft survival, and economic cost. In total, 30 patients were randomized to receive cinacalcet (n=15) or subtotal parathyroidectomy (n=15). At 12 months, ten of 15 patients in the cinacalcet group and 15 of 15 patients in the parathyroidectomy group (P=0.04) achieved normocalcemia. Normalization of serum phosphate concentration occurred in almost all patients. Subtotal parathyroidectomy induced greater reduction of iPTH and associated with a significant increase in femoral neck bone mineral density; vascular calcification remained unchanged in both groups. The most frequent adverse events were digestive intolerance in the cinacalcet group and hypocalcemia in the parathyroidectomy group. Surgery would be more cost effective than cinacalcet if cinacalcet duration reached 14 months. All patients were alive with a functioning graft at the end of follow-up. In conclusion, subtotal parathyroidectomy was superior to cinacalcet in controlling hypercalcemia in these patients with kidney transplants and persistent hyperparathyroidism.

Concepts: Chronic kidney disease, Kidney, Nephrology, Vitamin D, Parathyroid hormone, Organ transplant, Hypoparathyroidism, Hyperparathyroidism