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      Activation of the Somatotropic Axis by Testosterone in Adult Men: Evidence for a Role of Hypothalamic Growth Hormone-Releasing Hormone

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          Abstract

          Testosterone (T) is known to affect the growth hormone (GH) axis. However, the mechanisms underlying the activation of GH secretion by T still remain to be clarified. Available data in animals and humans have shown that withdrawal of somatostatin (SRIH) infusion induces a GH-releasing hormone (GHRH)-mediated rebound release of GH, and there is accumulating evidence that SRIH infusion withdrawal may be a useful test to probe the GHRH function in vivo. With the aim of investigating whether the stimulatory effect of androgens on GH release in man could be accounted for by activation of the hypothalamic GHRH tone, we evaluated the plasma GH response to SRIH withdrawal in 10 patients aged 29.6 ± 2.4 years (mean ± SEM), diagnosed with hypergonadotropic hypogonadism, before and after a 6-month replacement therapy with T enanthate (250 mg every 3 weeks, i.m.), and in 10 healthy men, aged 26.7 ± 2.8 years. To verify whether the modulation of GH secretion by T could also be mediated through changes in SRIH tone and/or pituitary releasable pool, we examined GH secretory responses to combined GHRH and L-arginine (ARG) in the same individuals. Basal plasma concentrations of GH (0.48 ± 0.11 µg/l) and IGF-I (23.79 ± 1.83 nmol/l) were significantly lower in untreated hypogonadal patients than in healthy men, and significantly increased after T replacement therapy (GH 1.13 ± 0.28 µg/l; IGF-I 28.71 ± 1.46 nmol/l). The mean ΔGH peak after SRIH withdrawal recorded in untreated hypogonadal men (2.65 ± 0.86 µg/l) was significantly (p < 0.05) lower than that observed in healthy men (6.53 ± 1.33 µg/l) and significantly increased after T replacement therapy (5.52 ± 1.25 µg/l). The GH responses to GHRH combined with ARG (a functional SRIH antagonist) were not significantly different between healthy men and untreated hypogonadal patients, and were not significantly affected by T treatment. Plasma T and estradiol (E<sub>2</sub>) levels significantly correlated with ΔGH peak after SRIH withdrawal in healthy men and in T-treated hypogonadal patients, whereas in untreated patients they did not. No significant correlation was found between GH areas under the curve after GHRH + ARG test and T and E<sub>2</sub> plasma levels in either healthy men or in hypogonadal patients (both before and after T replacement). These findings are consistent with the view that in humans the stimulatory action of T on the GH axis appears to be mediated at the hypothalamic level primarily by promoting GHRH function.

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          Most cited references 13

          • Record: found
          • Abstract: not found
          • Article: not found

          Pathophysiology of the Neuroregulation of Growth Hormone Secretion in Experimental Animals and the Human

           A Giustina (1998)
            Bookmark
            • Record: found
            • Abstract: not found
            • Article: not found

            Reliability of provocative tests to assess growth hormone secretory status. Study in 472 normally growing children

             E. Ghigo (1996)
              Bookmark
              • Record: found
              • Abstract: not found
              • Article: not found

              Comparison between Insulin-Induced Hypoglycemia and Growth Hormone (GH)-Releasing Hormone + Arginine as Provocative Tests for the Diagnosis of GH Deficiency in Adults

               G Aimaretti (1998)
                Bookmark

                Author and article information

                Journal
                NEN
                Neuroendocrinology
                10.1159/issn.0028-3835
                Neuroendocrinology
                S. Karger AG
                0028-3835
                1423-0194
                2003
                June 2003
                08 July 2003
                : 77
                : 6
                : 380-387
                Affiliations
                Department of Biomedical Sciences and Advanced Therapies, Section of Endocrinology, University of Ferrara, Ferrara, Italy
                Article
                71310 Neuroendocrinology 2003;77:380–387
                10.1159/000071310
                12845224
                © 2003 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: 4, Tables: 1, References: 41, Pages: 8
                Categories
                Regulation of Growth Hormones

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