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      Effects of Changes in Nutritional Conditions on Timing of Puberty: Clinical Evidence from Adopted Children and Experimental Studies in the Male Rat

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          Abstract

          Among 32 patients with idiopathic central precocious puberty seen during a 3-year period, 1/4 were adopted children from developing countries who showed early sexual maturation during the catch-up process following their arrival in Belgium. To study the possible mechanism accounting for such clinical observations, we used the male rat as a model, and evaluated the effect of variations in early nutritional conditions, by manipulating litter size, on hypothalamic and testicular maturation. We had shown previously that, in the male rat, onset of puberty was preceded, between 15 and 25 days of age, by a transiently increased activation of N-methyl- D-paspartate receptors involved in a facilitatory control of pulsatile secretion of gonadotropin-releasing hormone. We also showed that the proportion of elongated spermatids in testicular cell homogenates increased between 25 and 45 days of age. When compared to pups of a small litter (6/dam), those of a large litter (14/dam) showed a reduced growth rate (1.9 vs. 3.5 g/day) before weaning (21 days), whereas they grew at a similar rate (5.6 vs. 4.7 g/day) after weaning. At 35 days of age, the animals raised in the large litter showed evidence of delayed hypothalamic and testicular maturation when compared to animals from the small litter. Reduction of litter size at 17 days allowed food-restricted pups of a large litter to resume a normal growth rate before weaning. Then, the level of hypothalamic and testicular maturation studied at 20 and 35 days was similar to that of rats raised in a small litter, although these well-fed animals were significantly bigger than those from the large litter refed at 17 days. Serum concentrations of insulin-like growth factor I were lower in food-restricted animals refed after weaning than in rats well-fed or refed before weaning. When food-restricted pups were allowed to resume a normal growth rate at 12 days, they showed, at 15 days, evidence of earlier hypothalamic maturation than well-fed rats, despite being significantly smaller. In summary, the increase in growth rate resulting from unrestricted feeding after nutritional deprivation was associated with accelerated hypothalamic and testicular maturation which were advanced for body size. However, such an effect was only observed when refeeding occurred before weaning, indicating that hypothalamic maturation was sensitive to changes in nutritional conditions and growth rate during a critical period preceding the onset of puberty.

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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
          978-3-8055-5742-9
          978-3-318-01970-4
          1663-2818
          1663-2826
          1992
          1992
          03 December 2008
          : 38
          : Suppl 1
          : 97-105
          Affiliations
          aDepartment of Pediatrics, and bRadioimmunoassay Laboratory, University of Liège, Belgium
          Article
          182579 Horm Res 1992;38:97–105
          10.1159/000182579
          1295822
          © 1992 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
          Pages: 9
          Categories
          The Third hGH Symposium Sorrento 1992

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