Effect of thyroxine on the inactivation of thyrotrophin releasing hormone by rat and human plasma

A. Dupont, F. Labrie, L. Levasseur, J. H. Dussault, Andrew V Schally

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The inactivation of synthetic [ 3H]thyrotrophin releasing hormone (TRH) by plasma was studied in rats treated with propylthiouracil (PTU) alone or with PTU and thyroxine. 48 h after the onset of treatment with thyroxine, the capacity of rat plasma to inactivate [ 3H]TRH was significantly increased. The percentage of deamidation of TRH to TRH free acid was increased 2 fold after 4 days of administration of thyroid hormone. The inactivation of TRH by plasma from hypothyroid patients was compared to that obtained from hyperthyroid patients. Extraction of human plasma incubated with [ 3H]TRH, followed by thin layer electrophoresis, showed that transformation of [ 3H]TRH into TRH free acid was 44% higher in plasma from hyperthyroid than from hypothyroid patients (P<0.05). These data suggest that the inactivation process of TRH by blood proteins could be an important factor in the regulation of the hypothalamo hypophyseal thyroid axis in rat and man.

Original languageEnglish
Pages (from-to)323-330
Number of pages8
JournalClinical Endocrinology
Issue number4
StatePublished - Dec 1 1976
Externally publishedYes


ASJC Scopus subject areas

  • Endocrinology

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