TSH response pattern to TRH test and optimum time of blood sampling in sporadic euthyroid goitre

Attempts were made to estimate the response pattern of thyrotrophin (TSH) to thyrotrophin-releasing hormone (TRH) and the optimum time of blood sampling in patients with sporadic euthyroid goitre. Of the 65 subjects studied, 21 served as a reference group and 44 were patients with sporadic euthyroid goitres, divided into diagnostic subgroups according to type of goitre. Patients with a single autonomous thyroid adenoma were excluded. The classification of goitre was based on clinical features, thyroid function tests, thyroid imaging studies using 99mTc pertechnetate uptake, and examination of thyroid specimens originating from selective goitre resection carried out after the laboratory investigations. A standardized i.v. TRH test was performed in all probands and the TSH response was followed for 60 min postinjection. There was a definite trend towards lack of response with increasing nodularity of the thyroid gland. Moreover, no further information concerning the TSH response pattern was achieved by extending the blood sampling period beyond the +20 min limit of the time axis. The study lends support to the view that increasing functional autonomy is a general trend in goitre evolution.