Effect of selective goitre resection on absent thyrotrophin response to thyrotrophin releasing hormone in idiopathic euthyroid goitres.

Absent thyrotrophin (TSH) response to thyrotrophin releasing hormone (TRH) was found in ten of fifty consecutive nodular goitrous patients who were clinically and biochemically euthyroid. These ten patients together with a reference group engaging fifty-eight healthy individuals matched for sex, age, and geographic region form the basis of the present study. Patients with autonomously functioning single adenomata were excluded from the investigation. In the patient group, values of serum thyroxine (T4), free T4-index, and serum TSH did not differ significantly from those recorded in the reference group, whereas serum triiodothyronine was found to be significantly higher in the patients, although within the normal range. After selective resection of the goitre, the TSH responsiveness to TRH recovered completely. Routine indices of thyroid function, however, demonstrated no major deviation from pre-operative levels. During a follow-up period of 1 year, no systematic alterations were recorded in TSH response to TRH nor in the thyroid function tests, indicating maintenance of euthyroidism with restored normality within the pituitary-thyroid axis. The present study lends support to the view that increasing functional autonomy apparently is a common trend in goitre evolution in a non-endemic area.