Thyrotropin-releasing hormone radioimmunoassay in human serum and its application in thyroidal pathology

This paper presents the methodology of a specific radioimmunoassay of the TRH and the results obtained in patients with thyroid disorders. Synthetic TRH was labeled by iodine 125 at room temperature using a technique with Chloramine-T. The labeled compound was purified on a column chromatograph, and it was found the immunoreactivity of labeled-TRH was dependent on the elution fraction. Anti-TRH antibodies were obtained in rabbits after coupling the molecule with albumin using a diazotization method. In 62 normal patients, plasma TRH mean value and SD were found to be 137 +- 53 pg/ml. The clinical results show a significant decrease of TRH levels in hyperthyroid patients (Graves' disease and multinodular toxic goiter), and an increase in the few hypothyroid subjects examined, arguing strongly for the negative feed-back hypothesis. However, TRH levels were found to be increased in cold nodules (although with euthyroid function) and in the normal range in Plummers' disease, stating the problem of its pathogeny. Thus, the authors think that this TRH radioimmunoassay is very suitable and appropriate for routine use in human patients with thyroidal disorders. In the future is should be used as a dynamic test for the investigation of the kinetics of the hypothalamic TRH release. (orig./MG)