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1.
Pediatr Endocrinol Rev ; 17(1): 17-34, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31599133

RESUMO

Fibroblast growth factor 23 (FGF23), one of the endocrine fibroblast growth factors, is a principal regulator in the maintenance of serum phosphorus concentration. Binding to its cofactor αKlotho and a fibroblast growth factor receptor is essential for its activity. Its regulation and interaction with other factors in the bone-parathyroid-kidney axis is complex. FGF23 reduces serum phosphorus concentration through decreased reabsorption of phosphorus in the kidney and by decreasing 1,25 dihydroxyvitamin D (1,25(OH)2D) concentrations. Various FGF23-mediated disorders of renal phosphate wasting share similar clinical and biochemical features. The most common of these is X-linked hypophosphatemia (XLH). Additional disorders of FGF23 excess include autosomal dominant hypophosphatemic rickets, autosomal recessive hypophosphatemic rickets, fibrous dysplasia, and tumor-induced osteomalacia. Treatment is challenging, requiring careful monitoring and titration of dosages to optimize effectiveness and to balance side effects. Conventional therapy for XLH and other disorders of FGF23-mediated hypophosphatemia involves multiple daily doses of oral phosphate salts and active vitamin D analogs, such as calcitriol or alfacalcidol. Additional treatments may be used to help address side effects of conventional therapy such as thiazides to address hypercalciuria or nephrocalcinosis, and calcimimetics to manage hyperparathyroidism. The recent development and approval of an anti-FGF23 antibody, burosumab, for use in XLH provides a novel treatment option.


Assuntos
Fatores de Crescimento de Fibroblastos , Hipofosfatemia/terapia , Anticorpos Monoclonais/uso terapêutico , Raquitismo Hipofosfatêmico Familiar/fisiopatologia , Raquitismo Hipofosfatêmico Familiar/terapia , Fatores de Crescimento de Fibroblastos/genética , Fatores de Crescimento de Fibroblastos/metabolismo , Humanos , Hipofosfatemia/fisiopatologia , Osteomalacia/fisiopatologia , Osteomalacia/terapia , Fosfatos/metabolismo , Fosfatos/uso terapêutico
2.
J Bone Miner Res ; 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31652009

RESUMO

Autosomal dominant hypophosphatemic rickets (ADHR) is caused by mutations impairing cleavage of fibroblast growth factor 23 (FGF23). FGF23 gene expression increases during iron deficiency. In humans and mice with the ADHR mutation, iron deficiency results in increased intact FGF23 concentrations and hypophosphatemia. We conducted a prospective open label pilot clinical trial of oral iron replacement over 12 months in ADHR patients to test the hypothesis that oral iron administration would normalize FGF23 concentrations. Eligibility criteria included: FGF23 mutation; and either serum iron <50 µg/dL; or serum iron 50 to 100 µg/dL combined with hypophosphatemia and intact FGF23 >30 pg/mL at screening. Key exclusion criteria were kidney disease and pregnancy. Oral iron supplementation started at 65 mg daily and was titrated based on fasting serum iron concentration. The primary outcome was decrease in fasting intact FGF23 by ≥20% from baseline. Six adults (three male, three female) having the FGF23-R176Q mutation were enrolled; five completed the 12-month protocol. At baseline three of five subjects had severely symptomatic hypophosphatemia (phosphorus <2.5 mg/dL) and received calcitriol with or without phosphate concurrent with oral iron during the trial. The primary outcome was met by 4 of 5 (80%) subjects all by month 4, and 5 of 5 had normal intact FGF23 at month 12. Median (minimum, maximum) intact FGF23 concentration decreased from 172 (20, 192) pg/mL at baseline to 47 (17, 78) pg/mL at month 4 and 42 (19, 63) pg/mL at month 12. Median ferritin increased from 18.6 (7.7, 82.5) ng/mL at baseline to 78.0 (49.6, 261.0) ng/mL at month 12. During iron treatment, all three subjects with baseline hypophosphatemia normalized serum phosphorus, had markedly improved symptoms, and were able to discontinue calcitriol and phosphate. Oral iron repletion normalized FGF23 and phosphorus in symptomatic, iron-deficient ADHR subjects. Thus, the standard approach to ADHR should include recognition, treatment, and prevention of iron deficiency. © 2019 American Society for Bone and Mineral Research.

3.
Bone ; 127: 386-392, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31276850

RESUMO

BACKGROUND: X-linked hypophosphatemia (XLH) causes rickets, osteomalacia, skeletal deformities and growth impairment, due to elevated fibroblast growth factor 23 and hypophosphatemia. Conventional therapy requires high doses of phosphate salts combined with active vitamin D analogues. Risks of this regimen include nephrocalcinosis and secondary hyperparathyroidism or progression to tertiary (hypercalcemic) hyperparathyroidism. METHODS: The primary goals were to estimate the prevalence of hyperparathyroidism and to characterize parathyroidectomy outcomes regarding hypercalcemia among XLH patients. XLH patients attending our center from 1/2000 to 12/2017 were included in a retrospective chart review. Prevalence of nephrocalcinosis and eGFR < 60 ml/min/1.73m2 was also assessed. RESULTS: Of 104 patients with XLH, 84 had concurrent measurements of calcium and PTH (40 adults and 44 children). Of these, 70/84 (83.3%), had secondary or tertiary hyperparathyroidism at any time point. Secondary hyperparathyroidism was persistent in 62.2% of those with data at multiple timepoints. Tertiary hyperparathyroidism had an overall prevalence of 14/84 (16.7%) patients. Parathyroidectomy was performed in 8/84 (9.5%) of the total population. After parathyroidectomy, persistent or recurrent tertiary hyperparathyroidism was detected in 6/8 (75%) patients at a median of 6 years (from 0 to 29 years). One patient had chronic post-surgical hypoparathyroidism and one patient remained normocalcemic 4 years after surgery. Nephrocalcinosis was more prevalent in patients with tertiary hyperparathyroidism than those without (60.0% vs 18.6%). Chronic kidney disease (eGFR < 60 ml/min/1.73m2) was also more prevalent in patients with tertiary hyperparathyroidism than those without (35.7% vs 1.5%). CONCLUSION: The majority of patients with XLH develop secondary hyperparathyroidism during treatment with phosphate and active vitamin D. A significant proportion develops tertiary hyperparathyroidism and most have recurrence or persistence of hypercalcemia after surgery.

4.
Calcif Tissue Int ; 105(3): 271-284, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31165191

RESUMO

Burosumab, a fully human monoclonal antibody to FGF23, is the only approved treatment for X-linked hypophosphatemia (XLH), a rare genetic disorder characterized by renal phosphate wasting and substantial cumulative musculoskeletal morbidity. During an initial 24-week randomized, controlled trial, 134 adults with XLH received burosumab 1 mg/kg (n = 68) or placebo (n = 66) every 4 weeks. After 24 weeks, all subjects received open-label burosumab until week 48. This report describes the efficacy and safety of burosumab during the open-label treatment period. From weeks 24-48, serum phosphorus concentrations remained normal in 83.8% of participants who received burosumab throughout and were normalized in 89.4% who received burosumab after placebo. By week 48, 63.1% of baseline fractures/pseudofractures healed fully with burosumab, compared with 35.2% with burosumab after placebo. In both groups, burosumab was associated with clinically significant and sustained improvement from baseline to week 48 in scores for patient-reported outcomes of stiffness, pain, physical function, and total distance walked in 6 min. Rates of adverse events were similar for burosumab and placebo. There were no fatal adverse events or treatment-related serious adverse events. Nephrocalcinosis scores did not change from baseline by more than one grade at either week 24 or 48. These data demonstrate that in participants with XLH, continued treatment with burosumab is well tolerated and leads to sustained correction of serum phosphorus levels, continued healing of fractures and pseudofractures, and sustained improvement in key musculoskeletal impairments.

5.
Lancet ; 393(10189): 2416-2427, 2019 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-31104833

RESUMO

BACKGROUND: X-linked hypophosphataemia in children is characterised by elevated serum concentrations of fibroblast growth factor 23 (FGF23), hypophosphataemia, rickets, lower extremity bowing, and growth impairment. We compared the efficacy and safety of continuing conventional therapy, consisting of oral phosphate and active vitamin D, versus switching to burosumab, a fully human monoclonal antibody against FGF23, in paediatric X-linked hypophosphataemia. METHODS: In this randomised, active-controlled, open-label, phase 3 trial at 16 clinical sites, we enrolled children with X-linked hypophosphataemia aged 1-12 years. Key eligibility criteria were a total Thacher rickets severity score of at least 2·0, fasting serum phosphorus lower than 0·97 mmol/L (3·0 mg/dL), confirmed PHEX (phosphate-regulating endopeptidase homolog, X-linked) mutation or variant of unknown significance in the patient or a family member with appropriate X-linked dominant inheritance, and receipt of conventional therapy for at least 6 consecutive months for children younger than 3 years or at least 12 consecutive months for children older than 3 years. Eligible patients were randomly assigned (1:1) to receive either subcutaneous burosumab starting at 0·8 mg/kg every 2 weeks (burosumab group) or conventional therapy prescribed by investigators (conventional therapy group). Both interventions lasted 64 weeks. The primary endpoint was change in rickets severity at week 40, assessed by the Radiographic Global Impression of Change global score. All patients who received at least one dose of treatment were included in the primary and safety analyses. The trial is registered with ClinicalTrials.gov, number NCT02915705. FINDINGS: Recruitment took place between Aug 3, 2016, and May 8, 2017. Of 122 patients assessed, 61 were enrolled. Of these, 32 (18 girls, 14 boys) were randomly assigned to continue receiving conventional therapy and 29 (16 girls, 13 boys) to receive burosumab. For the primary endpoint at week 40, patients in the burosumab group had significantly greater improvement in Radiographic Global Impression of Change global score than did patients in the conventional therapy group (least squares mean +1·9 [SE 0·1] with burosumab vs +0·8 [0·1] with conventional therapy; difference 1·1, 95% CI 0·8-1·5; p<0·0001). Treatment-emergent adverse events considered possibly, probably, or definitely related to treatment by the investigator occurred more frequently with burosumab (17 [59%] of 29 patients in the burosumab group vs seven [22%] of 32 patients in the conventional therapy group). Three serious adverse events occurred in each group, all considered unrelated to treatment and resolved. INTERPRETATION: Significantly greater clinical improvements were shown in rickets severity, growth, and biochemistries among children with X-linked hypophosphataemia treated with burosumab compared with those continuing conventional therapy. FUNDING: Ultragenyx Pharmaceutical and Kyowa Kirin International.


Assuntos
Anticorpos Monoclonais/uso terapêutico , Raquitismo Hipofosfatêmico Familiar/tratamento farmacológico , Fatores Imunológicos/uso terapêutico , Estatura , Criança , Desenvolvimento Infantil , Pré-Escolar , Raquitismo Hipofosfatêmico Familiar/diagnóstico , Feminino , Humanos , Lactente , Masculino , Índice de Gravidade de Doença , Resultado do Tratamento
6.
J Bone Miner Res ; 34(8): 1436-1445, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30889272

RESUMO

In autosomal dominant osteopetrosis type 2 (ADO2) CLCN7 mutations cause impaired osteoclast function. Severe consequences include skeletal fragility despite high bone mass, osteomyelitis, osteonecrosis, bone marrow failure, and severe cranial nerve impingement. There is no effective medical treatment for ADO2. We recruited subjects with ADO2 into a 14-week, open-label, pilot clinical trial of interferon gamma-1b. Doses were titrated based on tolerability and if fasting serum C-telopeptide (CTX) was <25% above baseline at week 8, targeting doses of 100 µg/m2 three times a week. The primary outcomes were change from baseline in CTX and N-telopeptide/creatinine ratio (NTX/Cr) at week 14. Secondary outcomes included changes in urine calcium/creatinine ratio, bone formation markers and tolerability. Nine adults and three children were recruited. Severe manifestations of ADO2 included histories of fractures (100%), osteomyelitis (16.7%), vision loss (50%), and anemia (58.3%). Baseline CTX and NTX/Cr were generally low-normal. Procollagen type I N-terminal propeptide was elevated or in the upper-normal range in 11 of 12 (91.6%) subjects. Elevations of aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were common. One subject withdrew due to rash. Five subjects achieved doses of 50 µg/m2 3 days a week, while six reached the full dose of 100 µg/m2 3 days a week. Only 3 of 11 (27.3%) completing subjects achieved the primary outcome of increasing CTX ≥25% above baseline at week 14. The mean ± SD change from baseline in CTX at week 14 was +2.2% ± 43.2%, p = 0.86). Likewise, there was no significant change in NTX/Cr (mean change -2.1%, p = 0.81). Interferon gamma-1b was poorly tolerated. Most subjects had adverse events, and the Mental Health and Mental Component Scales of the SF-36v2 health survey declined slightly (p < 0.05). Over 14 weeks, interferon gamma-1b failed to significantly increase bone turnover markers in ADO2 and was poorly tolerated. Consequently, interferon gamma-1b is unlikely to be effective for decreasing bone mass in ADO2. © 2019 American Society for Bone and Mineral Research.

7.
Lancet Diabetes Endocrinol ; 7(3): 189-199, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30638856

RESUMO

BACKGROUND: Children with X-linked hypophosphataemia have high concentrations of circulating phosphatonin fibroblast growth factor 23 (FGF23), which causes renal phosphate wasting and hypophosphataemia, rickets, skeletal deformities, and growth impairment. Burosumab, a human monoclonal antibody against FGF23, improves phosphate homoeostasis and rickets in children aged 5-12 years with X-linked hypophosphataemia. We aimed to assess the safety and efficacy of burosumab in younger children with X-linked hypophosphataemia. METHODS: In this open-label, phase 2 trial at three hospitals in the USA, children (aged 1-4 years) with X-linked hypophosphataemia received burosumab (0·8 mg/kg) via subcutaneous injection every 2 weeks for 64 weeks. The dose was increased to 1·2 mg/kg if two consecutive pre-dose serum phosphorus concentrations were below 1·03 mmol/L (3·2 mg/dL), serum phosphorus had increased by less than 0·16 mmol/L (<0·5 mg/dL) from baseline, and a dose of burosumab had not been missed. Participants could continue to receive burosumab for up to an additional 96 weeks during the extension period. Key inclusion criteria were age 1-4 years at the time of informed consent; fasting serum phosphorus concentration of less than 0·97 mmol/L (3·0 mg/dL); serum creatinine 8·8-35·4 µmol/L (0·1-0·4 mg/dL); radiographic evidence of rickets (at least five participants were required to have a Thacher Rickets Severity Score of ≥1·5 at the knee); and a confirmed PHEX mutation or a variant of unknown significance in the patient or direct relative also affected with X-linked hypophosphataemia. Conventional therapy was stopped upon enrolment. The coprimary endpoints were safety and change from baseline to week 40 in fasting serum phosphorus concentrations. Changes in rickets severity from baseline to weeks 40 and 64 (assessed radiographically using Thacher Rickets Severity Score and an adaptation of the Radiographic Global Impression of Change), and recumbent length or standing height, were key secondary outcomes. This trial is registered with ClinicalTrials.gov, number NCT02750618, and is ongoing. FINDINGS: Between May 16, 2016, and June 10, 2016, we enrolled 13 children with X-linked hypophosphataemia. All 13 children completed 64 weeks of treatment and were included in the efficacy and safety analysis; none exceeded 70 weeks of treatment at the time of analysis. Serum phosphorus least squares mean increase from baseline to week 40 of treatment was 0·31 mmol/L (SE 0·04; 95% CI 0·24-0·39; 0·96 mg/dL [SE 0·12]; p<0·0001). All patients had at least one adverse event. 14 treatment-related adverse events, mostly injection site reactions, occurred in five children. One serious adverse event considered unrelated to treatment (tooth abscess) occurred in a child with a history of tooth abscess. All other adverse events were mild to moderate, except a severe food allergy considered unrelated to treatment. No instances of nephrocalcinosis or noteworthy changes in the results of a standard safety chemistry panel emerged. Total Thacher Rickets Severity Score decreased by a least squares mean of -1·7 (SE 0·1; p<0·0001) from baseline to week 40 and by -2·0 (SE 0·1; p<0·0001) by week 64. The Radiographic Global Impression of Change score also indicated significant improvement, with a least squares mean score of +2·3 (SE 0·1) at week 40 and +2·2 (0·1) at week 64 (both p<0·0001). Mean length or standing height Z score was maintained from baseline to week 64. INTERPRETATION: Burosumab had a favourable safety profile, increased serum phosphorus, and improved rickets and prevented early declines in growth in children aged 1-4 years with X-linked hypophosphataemia. These findings could substantially alter the treatment of young children with X-linked hypophosphataemia. FUNDING: Ultragenyx Pharmaceutical and Kyowa Kirin International.

8.
Br J Clin Pharmacol ; 2018 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-30207609

RESUMO

The most common heritable disorder of renal phosphate wasting, X-linked hypophosphataemia (XLH), was discovered to be caused by inactivating mutations in the phosphate regulating gene with homology to endopeptidases on the X-chromosome (PHEX) gene in 1995. Although the exact molecular mechanisms by which PHEX mutations cause disturbed phosphate handling in XLH remain unknown, focus for novel therapies has more recently been based upon the finding that the bone-produced phosphaturic hormone fibroblast growth factor-23 is elevated in XLH patient plasma. Previous treatment strategies for XLH were based upon phosphate repletion plus active vitamin D analogues, which are difficult to manage, fail to address the primary pathogenesis of the disease, and can have deleterious side effects. A novel therapy for XLH directly targeting fibroblast growth factor-23 via a humanized monoclonal antibody (burosumab-twza/CRYSVITA, henceforth referred to just as burosumab) has emerged as an effective, and recently approved, pharmacological treatment for both children and adults. This review will provide an overview of the clinical manifestations of XLH, the molecular pathophysiology, and summarize its current treatment.

9.
J Am Soc Nephrol ; 29(10): 2583-2592, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30217807

RESUMO

BACKGROUND: Fibroblast growth factor 23 (FGF23), a bone-derived hormone that regulates phosphorus and vitamin D metabolism, contributes to the pathogenesis of mineral and bone disorders in CKD and is an emerging cardiovascular risk factor. Central elements of FGF23 regulation remain incompletely understood; genetic variation may help explain interindividual differences. METHODS: We performed a meta-analysis of genome-wide association studies of circulating FGF23 concentrations among 16,624 participants of European ancestry from seven cohort studies, excluding participants with eGFR<30 ml/min per 1.73 m2 to focus on FGF23 under normal conditions. We evaluated the association of single-nucleotide polymorphisms (SNPs) with natural log-transformed FGF23 concentration, adjusted for age, sex, study site, and principal components of ancestry. A second model additionally adjusted for BMI and eGFR. RESULTS: We discovered 154 SNPs from five independent regions associated with FGF23 concentration. The SNP with the strongest association, rs17216707 (P=3.0×10-24), lies upstream of CYP24A1, which encodes the primary catabolic enzyme for 1,25-dihydroxyvitamin D and 25-hydroxyvitamin D. Each additional copy of the T allele at this locus is associated with 5% higher FGF23 concentration. Another locus strongly associated with variations in FGF23 concentration is rs11741640, within RGS14 and upstream of SLC34A1 (a gene involved in renal phosphate transport). Additional adjustment for BMI and eGFR did not materially alter the magnitude of these associations. Another top locus (within ABO, the ABO blood group transferase gene) was no longer statistically significant at the genome-wide level. CONCLUSIONS: Common genetic variants located near genes involved in vitamin D metabolism and renal phosphate transport are associated with differences in circulating FGF23 concentrations.

10.
J Bone Miner Res ; 33(8): 1383-1393, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29947083

RESUMO

In X-linked hypophosphatemia (XLH), inherited loss-of-function mutations in the PHEX gene cause excess circulating levels of fibroblast growth factor 23 (FGF23), leading to lifelong renal phosphate wasting and hypophosphatemia. Adults with XLH present with chronic musculoskeletal pain and stiffness, short stature, lower limb deformities, fractures, and pseudofractures due to osteomalacia, accelerated osteoarthritis, dental abscesses, and enthesopathy. Burosumab, a fully human monoclonal antibody, binds and inhibits FGF23 to correct hypophosphatemia. This report summarizes results from a double-blind, placebo-controlled, phase 3 trial of burosumab in symptomatic adults with XLH. Participants with hypophosphatemia and pain were assigned 1:1 to burosumab 1 mg/kg (n = 68) or placebo (n = 66) subcutaneously every 4 weeks (Q4W) and were comparable at baseline. Across midpoints of dosing intervals, 94.1% of burosumab-treated participants attained mean serum phosphate concentration above the lower limit of normal compared with 7.6% of those receiving placebo (p < 0.001). Burosumab significantly reduced the Western Ontario and the McMaster Universities Osteoarthritis Index (WOMAC) stiffness subscale compared with placebo (least squares [LS] mean ± standard error [SE] difference, -8.1 ± 3.24; p = 0.012). Reductions in WOMAC physical function subscale (-4.9 ± 2.48; p = 0.048) and Brief Pain Inventory worst pain (-0.5 ± 0.28; p = 0.092) did not achieve statistical significance after Hochberg multiplicity adjustment. At week 24, 43.1% (burosumab) and 7.7% (placebo) of baseline active fractures were fully healed; the odds of healed fracture in the burosumab group was 16.8-fold greater than that in the placebo group (p < 0.001). Biochemical markers of bone formation and resorption increased significantly from baseline with burosumab treatment compared with placebo. The safety profile of burosumab was similar to placebo. There were no treatment-related serious adverse events or meaningful changes from baseline in serum or urine calcium, intact parathyroid hormone, or nephrocalcinosis. These data support the conclusion that burosumab is a novel therapeutic addressing an important medical need in adults with XLH.© 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.

11.
N Engl J Med ; 378(21): 1987-1998, 2018 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-29791829

RESUMO

BACKGROUND: X-linked hypophosphatemia is characterized by increased secretion of fibroblast growth factor 23 (FGF-23), which leads to hypophosphatemia and consequently rickets, osteomalacia, and skeletal deformities. We investigated burosumab, a monoclonal antibody that targets FGF-23, in patients with X-linked hypophosphatemia. METHODS: In an open-label, phase 2 trial, we randomly assigned 52 children with X-linked hypophosphatemia, in a 1:1 ratio, to receive subcutaneous burosumab either every 2 weeks or every 4 weeks; the dose was adjusted to achieve a serum phosphorus level at the low end of the normal range. The primary end point was the change from baseline to weeks 40 and 64 in the Thacher rickets severity total score (ranging from 0 to 10, with higher scores indicating greater disease severity). In addition, the Radiographic Global Impression of Change was used to evaluate rachitic changes from baseline to week 40 and to week 64. Additional end points were changes in pharmacodynamic markers, linear growth, physical ability, and patient-reported outcomes and the incidence of adverse events. RESULTS: The mean Thacher rickets severity total score decreased from 1.9 at baseline to 0.8 at week 40 with every-2-week dosing and from 1.7 at baseline to 1.1 at week 40 with every-4-week dosing (P<0.001 for both comparisons); these improvements persisted at week 64. The mean serum phosphorus level increased after the first dose in both groups, and more than half the patients in both groups had levels within the normal range (3.2 to 6.1 mg per deciliter [1.0 to 2.0 mmol per liter]) by week 6. Stable serum phosphorus levels were maintained through week 64 with every-2-week dosing. Renal tubular phosphate reabsorption increased from baseline in both groups, with an overall mean increase of 0.98 mg per deciliter (0.32 mmol per liter). The mean dose of burosumab at week 40 was 0.98 mg per kilogram of body weight with every-2-week dosing and 1.50 mg per kilogram with every-4-week dosing. Across both groups, the mean serum alkaline phosphatase level decreased from 459 U per liter at baseline to 369 U per liter at week 64. The mean standing-height z score increased in both groups, with greater improvement seen at all time points with every-2-week dosing (an increase from baseline of 0.19 at week 64) than with every-4-week dosing (an increase from baseline of 0.12 at week 64). Physical ability improved and pain decreased. Nearly all the adverse events were mild or moderate in severity. CONCLUSIONS: In children with X-linked hypophosphatemia, treatment with burosumab improved renal tubular phosphate reabsorption, serum phosphorus levels, linear growth, and physical function and reduced pain and the severity of rickets. (Funded by Ultragenyx Pharmaceutical and Kyowa Hakko Kirin; ClinicalTrials.gov number, NCT02163577 ; EudraCT number, 2014-000406-35 ).


Assuntos
Anticorpos Monoclonais/uso terapêutico , Raquitismo Hipofosfatêmico Familiar/tratamento farmacológico , Fatores de Crescimento de Fibroblastos/antagonistas & inibidores , Doenças Genéticas Ligadas ao Cromossomo X/tratamento farmacológico , Fosfatase Alcalina/sangue , Criança , Pré-Escolar , Raquitismo Hipofosfatêmico Familiar/metabolismo , Raquitismo Hipofosfatêmico Familiar/fisiopatologia , Feminino , Doenças Genéticas Ligadas ao Cromossomo X/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/fisiopatologia , Crescimento/efeitos dos fármacos , Humanos , Túbulos Renais/metabolismo , Articulação do Joelho/diagnóstico por imagem , Masculino , Manejo da Dor , Fósforo/sangue , Radiografia , Índice de Gravidade de Doença
12.
J Pediatr ; 199: 263-266, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29699796

RESUMO

The prevalence of nephrocalcinosis in persons with pseudohypoparathyroidism has not been systematically examined. We conducted a retrospective study of renal imaging and biochemical results in 19 patients with pseudohypoparathyroidism with 49 imaging assessments. No cases of nephrocalcinosis were identified. Routine screening for nephrocalcinosis in pseudohypoparathyroidism may not be necessary.

13.
J Endocr Soc ; 1(9): 1160-1167, 2017 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-29264571

RESUMO

Context: Hypercalcemia is reported as a rare finding in adrenal insufficiency, but is not well described in congenital adrenal hyperplasia (CAH). Methods: A retrospective chart review was conducted of patients with CAH diagnosed before the age of 2 years who had at least one recorded serum calcium measurement. Data from birth to 6 years of age were reviewed. Results: Of the 40 patients who met inclusion criteria, 33 (82.5%) had at least one elevated calcium concentration and 21 (53%) had two or more elevated calcium concentrations. Of the 126 elevated serum calcium concentrations, the median was 10.9 mg/dL (range, 10.6 to 14.2 mg/dL). Median age at the last elevated calcium measurement was 5 months (range, 0.3 to 46 months). Serum calcium concentration was inversely related to age (r = -0.124; P = 0.004). Overall, calcium level positively correlated with 17-hydroxyprogesterone (17OHP) concentration (r = 0.170; P = 0.003), and this remained significant after adjusting for age (P < 0.05). However, patients had hypercalcemia with both high and low 17OHP concentrations. Serum calcium concentration also was positively related to glucocorticoid (r = 0.196; P = 0.012) and fludrocortisone (r = 0.229; P = 0.003) doses, and remained significant after age adjustment. Only seven patients were evaluated for hypercalciuria. Of these, six had at least one period of documented hypercalciuria. Three patients had nephrocalcinosis on renal ultrasound. Conclusion: Children with CAH are at risk for developing hypercalcemia, hypercalciuria, and nephrocalcinosis. Further studies are needed to determine the broader prevalence and the etiology of hypercalcemia in CAH.

14.
Bone ; 97: 287-292, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28167344

RESUMO

OBJECTIVE: Hypophosphatemia occurs with inadequate dietary intake, malabsorption, increased renal excretion, or shifts between intracellular and extracellular compartments. We noticed the common finding of amino-acid based elemental formula [EF] use in an unexpected number of cases of idiopathic hypophosphatemia occurring in infants and children evaluated for skeletal disease. We aimed to fully characterize the clinical profiles in these cases. METHODS: A retrospective chart review of children with unexplained hypophosphatemia was performed as cases accumulated from various centres in North America and Ireland. Data were analyzed to explore any relationships between feeding and biochemical or clinical features, effects of treatment, and to identify a potential mechanism. RESULTS: Fifty-one children were identified at 17 institutions with EF-associated hypophosphatemia. Most children had complex illnesses and had been solely fed Neocate® formula products for variable periods of time prior to presentation. Feeding methods varied. Hypophosphatemia was detected during evaluation of fractures or rickets. Increased alkaline phosphatase activity and appropriate renal conservation of phosphate were documented in nearly all cases. Skeletal radiographs demonstrated fractures, undermineralization, or rickets in 94% of the cases. Although the skeletal disease had often been attributed to underlying disease, most all improved with addition of supplemental phosphate or change to a different formula product. CONCLUSION: The observed biochemical profiles indicated a deficient dietary supply or severe malabsorption of phosphate, despite adequate formula composition. When transition to an alternate formula was possible, biochemical status improved shortly after introduction to the alternate formula, with eventual improvement of skeletal abnormalities. These observations strongly implicate that bioavailability of formula phosphorus may be impaired in certain clinical settings. The widespread nature of the findings lead us to strongly recommend careful monitoring of mineral metabolism in children fed EF. Transition to alternative formula use or implementation of phosphate supplementation should be performed cautiously with as severe hypocalcemia may develop.


Assuntos
Doenças Ósseas/induzido quimicamente , Hipofosfatemia/induzido quimicamente , Fórmulas Infantis/efeitos adversos , Fosfatase Alcalina/sangue , Doenças Ósseas/sangue , Doenças Ósseas/diagnóstico por imagem , Doenças Ósseas/urina , Cálcio/sangue , Criança , Pré-Escolar , Feminino , Humanos , Hipofosfatemia/sangue , Hipofosfatemia/diagnóstico por imagem , Hipofosfatemia/urina , Lactente , Masculino , Fósforo/sangue , Raquitismo/diagnóstico por imagem , Raquitismo/patologia
15.
Bone ; 86: 98-105, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26965530

RESUMO

Fibroblast growth factor 23 (FGF23) circulates as active protein and inactive fragments. Low iron status increases FGF23 gene expression, and iron deficiency is common. We hypothesized that in healthy premenopausal women, serum iron influences C-terminal and intact FGF23 concentrations, and that iron and FGF23 associate with bone mineral density (BMD). Serum iron, iron binding capacity, percent iron saturation, phosphorus, and other biochemistries were measured in stored fasting samples from healthy premenopausal white (n=1898) and black women (n=994), age 20-55years. Serum C-terminal and intact FGF23 were measured in a subset (1631 white and 296 black women). BMD was measured at the lumbar spine and femur neck. Serum phosphorus, calcium, alkaline phosphatase and creatinine were lower in white women than black women (p<0.001). Serum iron (p<0.0001) and intact FGF23 (p<0.01) were higher in white women. C-terminal FGF23 did not differ between races. Phosphorus correlated with intact FGF23 (white women, r=0.120, p<0.0001; black women r=0.163, p<0.01). However, phosphorus correlated with C-terminal FGF23 only in black women (r=0.157, p<0.01). Intact FGF23 did not correlate with iron. C-terminal FGF23 correlated inversely with iron (white women r=-0.134, p<0.0001; black women r=-0.188, p<0.01), having a steeper slope at iron <50mcg/dl than ≥50mcg/dl. Longitudinal changes in iron predicted changes in C-terminal FGF23. Spine BMD correlated with iron negatively (r=-0.076, p<0.01) in white women; femur neck BMD correlated with iron negatively (r=-0.119, p<0.0001) in black women. Both relationships were eliminated in weight-adjusted models. BMD did not correlate with FGF23. Serum iron did not relate to intact FGF23, but was inversely related to C-terminal FGF23. Intact FGF23 correlated with serum phosphorus. In weight-adjusted models, BMD was not related to intact FGF23, C-terminal FGF23 or iron. The influence of iron on FGF23 gene expression is not important in determining bone density in healthy premenopausal women.


Assuntos
Densidade Óssea , Fatores de Crescimento de Fibroblastos/sangue , Ferro/sangue , Pré-Menopausa/sangue , Adulto , Estudos de Coortes , Grupo com Ancestrais do Continente Europeu , Feminino , Colo do Fêmur/fisiologia , Humanos , Estudos Longitudinais , Vértebras Lombares/fisiologia , Análise Multivariada
16.
Blood Cells Mol Dis ; 57: 50-3, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26852655

RESUMO

A genome-wide association study was performed on 1130 premenopausal women to detect common variants associated with three serum iron-related phenotypes. Total iron binding capacity was strongly associated (p=10(-14)) with variants in and near the TF gene (transferrin), the serum iron transporting protein, and with variants in HFE (p=4×10(-7)), which encodes the human hemochromatosis gene. Association was also detected between percent iron saturation (p=10(-8)) and variants in the chromosome 6 region containing both HFE and SLC17A2, which encodes a phosphate transport protein. No significant associations were detected with serum iron, but variants in HFE were suggestive (p=10(-6)). Our results corroborate prior studies in older subjects and demonstrate that the association of these genetic variants with iron phenotypes can be detected in premenopausal women.


Assuntos
Hemocromatose/genética , Antígenos de Histocompatibilidade Classe I/genética , Ferro/sangue , Proteínas de Membrana/genética , Pré-Menopausa/genética , Proteínas Cotransportadoras de Sódio-Fosfato Tipo I/genética , Transferrina/genética , Adulto , Cromossomos Humanos Par 6/química , Grupo com Ancestrais do Continente Europeu , Feminino , Expressão Gênica , Estudo de Associação Genômica Ampla , Hemocromatose/sangue , Hemocromatose/etnologia , Hemocromatose/patologia , Proteína da Hemocromatose , Humanos , Pessoa de Meia-Idade , Fenótipo , Polimorfismo Genético , Pré-Menopausa/sangue , Análise de Sequência de DNA
17.
Bone Rep ; 5: 158-162, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28326356

RESUMO

X-linked hypophosphatemia (XLH) is characterized by lower extremity deformities that lead to bone and/or joint pain that result from decreased renal tubular reabsorption leading to hypophosphatemia caused by elevated levels of fibroblast growth factor 23 (FGF23). OBJECTIVE: Validate the use of SF-36v2 Health Survey (SF-36v2) and the Western Ontario and McMaster Osteoarthritis Index (WOMAC) to measure previously unstudied health-related quality of life (HRQoL) in XLH patients and determine the change in HRQoL before and after treatment with KRN23, a human monoclonal anti-FGF23 antibody. METHODS: Twenty-eight adult outpatients with XLH received up to four doses of KRN23 administered subcutaneously every 28 days. General HRQoL was measured with the SF-36v2 and condition-related HRQoL with the WOMAC at baseline and study endpoint as a secondary outcome of a Phase 1/2, open-label, multicenter, dose-escalation trial. RESULTS: Testing for scale discriminant validity and convergent-divergent validity supported the use of these scales in the assessment of HRQoL in XLH. Both instruments indicated impairment of physical function at baseline with all mean scores showing a trend to improved health at study endpoint compared to baseline. When corrected for multiple comparisons, the score for Role Limitations due to physical health on the SF-36v2 which measures the patient's perception of their own chronic functional impairments due to poor physical health remained significantly improved (P < 0.05), increasing to the mean score of US adults. For the WOMAC, Physical Functioning and Stiffness scores were significantly improved (P < 0.05). CONCLUSION: KRN23 administration was associated with significantly improved patient perception of their Physical Functioning and Stiffness due to their disease. This study demonstrates that the SF-36v2 and WOMAC are valid tools for assessing HRQoL in XLH.

18.
J Clin Pharmacol ; 56(4): 429-38, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26247790

RESUMO

X-linked hypophosphatemia (XLH) is an inherited metabolic bone disease with abnormally elevated serum FGF23 resulting in low renal maximum threshold for phosphate reabsorption, low serum phosphate (Pi) and 1,25-dihydroxyvitamin D levels with subsequent development of short stature and skeletal deformities. KRN23 is a novel human anti-FGF23 antibody for the treatment of XLH. The pharmacokinetics (PK) and pharmacodynamics (PD) models of KRN23 were assessed following subcutaneous dosing every 28 days over an initial 4-month dose escalation (0.05-0.6 mg/kg) and a subsequent 12-month titration period (0.1-1.0 mg/kg) in XLH adults. The PK of KRN23 was described by a 1-compartmental model with first-order absorption and elimination at doses ≥0.1 mg/kg. The elimination half-life was 17.8 days. Covariates did not affect KRN23 PK. Mean peak serum Pi was attained 7-10 days after dosing and progressively increased following each of the initial 4 doses with comparable peak values attained following the sixth through tenth doses with a slight decrease thereafter. A PK-PD model with a maximum effect (Emax ) and a time-varying effective concentration to reach 50% of Emax (EC50,t ) described data adequately. Typical Emax was 1.5 mg/dL. Typical EC50,t was 1780 ng/mL and 5999 ng/mL after first and last dose, respectively.


Assuntos
Anticorpos Monoclonais/administração & dosagem , Anticorpos Monoclonais/farmacocinética , Raquitismo Hipofosfatêmico Familiar/tratamento farmacológico , Adulto , Raquitismo Hipofosfatêmico Familiar/sangue , Feminino , Fatores de Crescimento de Fibroblastos/sangue , Meia-Vida , Humanos , Masculino , Pessoa de Meia-Idade , Fosfatos/sangue , Vitamina D/análogos & derivados , Vitamina D/sangue
19.
J Clin Pharmacol ; 56(2): 176-85, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26073451

RESUMO

In X-linked hypophosphatemia (XLH), serum fibroblast growth factor 23 (FGF23) is increased and results in reduced renal maximum threshold for phosphate reabsorption (TmP), reduced serum inorganic phosphorus (Pi), and inappropriately low normal serum 1,25 dihydroxyvitamin D (1,25[OH]2 D) concentration, with subsequent development of rickets or osteomalacia. KRN23 is a recombinant human IgG1 monoclonal antibody that binds to FGF23 and blocks its activity. Up to 4 doses of KRN23 were administered subcutaneously every 28 days to 28 adults with XLH. Mean ± standard deviation KRN23 doses administered were 0.05, 0.10 ± 0.01, 0.28 ± 0.06, and 0.48 ± 0.16 mg/kg. The mean time to reach maximum serum KRN23 levels was 7.0 to 8.5 days. The mean KRN23 half-life was 16.4 days. The mean area under the concentration-time curve (AUCn ) for each dosing interval increased proportionally with increases in KRN23 dose. The mean intersubject variability in AUCn ranged from 30% to 37%. The area under the effect concentration-time curve (AUECn ) for change from baseline in TmP per glomerular filtration rate, serum Pi, 1,25(OH)2 D, and bone markers for each dosing interval increased linearly with increases in KRN23 AUCn . Linear correlation between serum KRN23 concentrations and increase in serum Pi support KRN23 dose adjustments based on predose serum Pi concentration.


Assuntos
Anticorpos Monoclonais/farmacologia , Anticorpos Monoclonais/farmacocinética , Raquitismo Hipofosfatêmico Familiar/tratamento farmacológico , Adulto , Idoso , Anticorpos Monoclonais/administração & dosagem , Área Sob a Curva , Biomarcadores , Osso e Ossos/metabolismo , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fósforo/sangue , Adulto Jovem
20.
Bone ; 83: 267-275, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26657827

RESUMO

BACKGROUND: Adherence to oral bisphosphonates is often low, but even adherent patients may remain at elevated fracture risk. The goal of this study was to estimate the proportion of bisphosphonate-adherent women remaining at high risk of fracture. METHODS: A retrospective cohort of women aged 50years and older, adherent to oral bisphosphonates for at least two years was identified, and data were extracted from a multi-system health information exchange. Adherence was defined as having a dispensed medication possession ratio≥0.8. The primary outcome was clinical occurrence of: low trauma fracture (months 7-36), persistent T-score≤-2.5 (months 13-36), decrease in bone mineral density (BMD) at any skeletal site≥5%, or the composite of any one of these outcomes. RESULTS: Of 7435 adherent women, 3110 had either pre- or post-adherent DXA data. In the full cohort, 7% had an incident osteoporotic fracture. In 601 women having both pre- and post-adherent DXA to evaluate BMD change, 6% had fractures, 22% had a post-treatment T-score≤-2.5, and 16% had BMD decrease by ≥5%. The composite outcomes occurred in 35%. Incident fracture was predicted by age, previous fracture, and a variety of co-morbidities, but not by race, glucocorticoid treatment or type of bisphosphonate. CONCLUSION: Despite bisphosphonate adherence, 7% had incident osteoporotic fractures and 35% had either fracture, decreases in BMD, or persistent osteoporotic BMD, representing a substantial proportion of treated patients in clinical practices remaining at risk for future fractures. Further studies are required to determine the best achievable goals for osteoporosis therapy, and which patients would benefit from alternate therapies.


Assuntos
Difosfonatos/uso terapêutico , Osteoporose/tratamento farmacológico , Fraturas por Osteoporose/epidemiologia , Fraturas por Osteoporose/etiologia , Cooperação do Paciente , Idoso , Estudos de Coortes , Comorbidade , Demografia , Feminino , Humanos , Análise Multivariada , Fatores de Risco , Resultado do Tratamento
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