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      Reduced Bone Mineral Density and Radial Bone Growth in Young Rabbits Treated with Dexamethasone Eye Drops

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          Abstract

          Objective: To investigate the effect of dexamethasone eye drops on bone metabolism in newborn rabbits. Methods: Thirty-four 3-week-old rabbits had unilateral clear lens extraction and were randomized into three groups. Postoperatively, group 1 received high-dose and group 2 low-dose dexamethasone eye drops (average doses 0.27 and 0.10 mg/kg body weight/day, respectively). These rabbits also received a postoperative subconjunctival injection of betamethasone. Group 3 (control) received vehicle eye drops only. After 8 weeks of treatment, all animals were killed and the left femurs were isolated and subjected to peripheral quantitative computerized tomography (pQCT) and dual X-ray absorptiometry (DXA) analyses. Results: DXA showed that rabbits treated with either a high or low dose of dexamethasone eye drops had significantly reduced areal bone mineral density (BMD), area and total bone mineral content (BMC) of the femur. Measurements with pQCT demonstrated a dose-dependent reduction in cortical BMC, cortical volumetric BMD and cortical area. These effects were associated with an inhibition of radial femur growth, cortical thickness and periosteal and endosteal circumferences. Conclusion: Dexamethasone eye drops have systemic effects affecting several bone parameters in young rabbits. Any long-term systemic effects of ocular glucocorticoids need to be further studied.

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          Most cited references 15

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          Increased cortical bone mineral content but unchanged trabecular bone mineral density in female ERbeta(-/-) mice.

          Ovariectomy in young, growing rodents results in decreased trabecular bone mineral density (BMD) and increased radial growth of the cortical bone. Both of these effects are reversed by treatment with estrogen. The aim of the present study was to determine the physiological role of estrogen receptor-beta (ERbeta) on bone structure and bone mineral content (BMC). The BMC was increased in adult (11 weeks old), but not prepubertal (4 weeks old), female ERbeta(-/-) mice compared with wild-type (WT) mice. This increase in BMC in females was not due to increased trabecular BMD, but to an increased cross-sectional cortical bone area associated with a radial bone growth. Male ERbeta(-/-) mice displayed no bone abnormalities compared with WT mice. Ovariectomy decreased the trabecular BMD to the same extent in adult female ERbeta(-/-) mice as in WT mice. The expression levels of osteoblast-associated genes - alpha1(I) collagen, alkaline phosphatase, and osteocalcin mRNAs - were elevated in bone from adult ERbeta(-/-) females compared with WT mice. These observations provide a possible explanation for the increased radial bone growth seen in female mutants, suggesting a repressive function for ERbeta in the regulation of bone growth during female adolescence. In summary, ERbeta is essential for the pubertal feminization of the cortical bone in female mice but is not required for the protective effect of estrogens on trabecular BMD.
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            Estrogen receptor specificity in the regulation of skeletal growth and maturation in male mice.

            Androgens may regulate the male skeleton directly through a stimulation of androgen receptors or indirectly through aromatization of androgens into estrogen and, thereafter, through stimulation of estrogen receptors (ERs). The relative importance of ER subtypes in the regulation of the male skeleton was studied in ERalpha-knockout (ERKO), ERbeta-knockout (BERKO), and double ERalpha/beta-knockout (DERKO) mice. ERKO and DERKO, but not BERKO, demonstrated decreased longitudinal as well as radial skeletal growth associated with decreased serum levels of insulin-like growth factor I. Therefore, ERalpha, but not ERbeta, mediates important effects of estrogen in the skeleton of male mice during growth and maturation.
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              Detection of growth suppression in children during treatment with intranasal beclomethasone dipropionate.

              Intranasal beclomethasone dipropionate (BDP) has generally been considered to have no systemic activity at recommended doses, but the potential for long-term effects on growth has not previously been evaluated. This study was undertaken to assess the effects of 1 year of treatment with intranasal BDP on growth in children. In this double-blind, randomized, parallel-group study, 100 prepubertal children 6 to 9 years old with perennial allergic rhinitis were treated with aqueous BDP 168 microg twice daily (n = 51) or placebo (n = 49) for 1 year. Subjects' baseline heights were required to be between the 5th and 95th percentile, and skeletal age as determined by left wrist radiograph was required to be within 2 years of chronological age. Washout periods for medications known to affect growth, including other forms of corticosteroids, were established, and these medications were prohibited during the study. However, short courses of oral prednisolone lasting no more than 7 days, and short courses of dermatologic corticosteroids lasting no more than 10 days, were allowed. Height was measured with a stadiometer after 1, 2, 4, 6, 8, 10, and 12 months of treatment. The hypothalamic-pituitary-adrenocortical axis was assessed by measurements of 8 AM basal cortisol concentrations and response to. 25 mg cosyntropin stimulation. The primary safety parameter was the rate of change in standing height. Statistical analyses were based on all randomized subjects who received at least 1 dose of medication (intent-to-treat principle). The rate of change in standing height was analyzed for all subjects who entered the study and for those completing the full 12 months of treatment (n = 80). The rate of change in standing height over the 1-year study was calculated as the slope of a linear regression line fitted to each subject's height measurements over time. Because there was a statistically significant between-group difference in standing height at baseline, an analysis of covariance was performed for all analyses of standing height data. Of the 100 subjects enrolled, 90 completed the study. The 2 treatment groups were generally comparable at baseline; however, at baseline, mean age and mean height were significantly greater in the BDP treatment group that the in placebo treatment group. In both analyses, overall growth rate was significantly slower in BDP-treated subjects than placebo-treated subjects. The mean change in standing height after 1 year was 5.0 cm in the BDP-treated subjects compared with 5.9 cm in the placebo-treated subjects. The difference in growth rates was evident as early as the 1-month treatment visit, suggesting that the effect on growth occurred initially. The growth-suppressive effect of BDP remained consistent across all age and gender subgroups, and among subjects with and without a previous history of corticosteroid use. Use of additional exogenous corticosteroids during the study was similar in both groups and did not affect the results. Because there was a baseline imbalance in height, a supplemental analysis of the differences in prestudy growth rates was performed. This analysis found no baseline imbalance in prestudy growth rates. To determine whether the difference in growth rates during the study could be attributed to preexisting growth rates, a z score analysis was performed. The heights of both groups were normalized at baseline and at the end of the study using the US National Center for Health Statistics data for mean and standard deviations of height. This analysis confirmed that the difference in growth rates between the 2 groups was primarily attributable to the treatment rather than to any preexisting difference in growth. Additional analyses confirmed that the results were not influenced by outlier values. No significant between-group difference were found in the hypothalamic-pituitary-adrenocortical axis assessments. No unusual adverse events were observed. (ABSTRACT
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                Author and article information

                Journal
                HRE
                Horm Res Paediatr
                10.1159/issn.1663-2818
                Hormone Research in Paediatrics
                S. Karger AG
                1663-2818
                1663-2826
                2005
                June 2005
                13 June 2005
                : 63
                : 4
                : 165-170
                Affiliations
                aSt. Erik’s Eye Hospital, Stockholm, bDivision of Endocrinology, Department of Internal Medicine, Sahlgrenska University Hospital, Gothenburg, and cAstrid Lindgren Children’s Hospital, Pediatric Endocrinology Unit, Karolinska Institute and Hospital, Stockholm, Sweden
                Article
                84684 Horm Res 2005;63:165–170
                10.1159/000084684
                15795513
                © 2005 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 1, Tables: 3, References: 23, Pages: 6
                Categories
                Original Paper

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