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      Dissociation of Thyrotropin and Prolactin Responsiveness to Thyrotropin Releasing Hormone Stimulation in L -Dopa Treated Parkinsonian Patients

      , , ,

      Hormone Research in Paediatrics

      S. Karger AG

      hTSH, hPRL, TRH, <italic>L</italic>-Dopa treatment, Parkinsonians

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          Abstract

          The hPRL, hTSH and T<sub>3</sub> response to thyrotropin releasing hormone (TRH) stimulation (200 µg i.v.) were studied in 8 parkinsonian patients under chronic L-dopa-carbidopa therapy. In 6 out of the 8 patients studied, treatment was stopped for a period of 2 weeks and the TRH stimulation test was repeated under similar experimental conditions. In the L-dopa-carbidopa treated patients basal hTSH levels and the hTSH response to TRH were significantly suppressed. By contrast, in the 6 patients 2 weeks after cessation of treatment, although basal hTSH levels were still suppressed, a normal hTSH response to TRH was observed. Neither the basal T3 and T4 concentrations, nor the T3 response to TRH were affected by the L-dopa-carbidopa treatment. In addition, basal hPRL levels as well as the hPRL response to TRH were within the normal range in the two groups of patients studied. Our study provides further support for a dopaminergic inhibitory action on the hypothalamo-hypophyseal-thyroidal axis (HHTA). The inhibition of basal hTSH secretion and the hTSH response to TRH by L-dopa, suggest that the blocking action of dopamine is exerted at the hypothalamic as well as at the pituitary level. In our hands, chronic administration of L-dopa did not affect either tonic hPRL secretion or the hPRL response to TRH. The dissociation or response to TRH under the same inhibitory action of dopaminergic stimulation can be interpreted as demonstrating a greater sensitivity of the pituitary thyrotrophs, than the prolactin secreting cells, to the blocking effect of dopamine.

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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
          1981
          1981
          25 November 2008
          : 15
          : 2
          : 78-87
          Affiliations
          Department of Neurology, Institute of Reproductive Endocrinology, Municipal Governmental Medical Center, University of Tel-Aviv, Israel
          Article
          179437 Horm Res 1981;15:78–87
          10.1159/000179437
          6799381
          © 1981 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: 10
          Categories
          Original Paper

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