Serum Thyrotropin Concentrations Under Basal Conditions and After Stimulation with Thyrotropin-Releasing Hormone in Idiopathic Non-toxic Goiter

Abstract

In order to investigate the role of thyrotropin (TSH) in goiter development and maintenance, the serum TSH concentration, the TSH response to thyrotropin-releasing hormone (TRH), and the increase in serum T3 after TRH were measured in 51 normal subjects and in 65 euthyroid patients with idiopathic nontoxic goiter. Fifteen patients had diffuse goiter, 47 multinodular goiter, and 3 an enlarged gland with a single non-functioning nodule. Serum thyrotropin (TSH) concentrations differed significantly in the two groups, the 95% range of the normal subjects was <0.2–2.0 μU/ml, and of the goitrous patients <0.2–4.5 μU/ml, 17 of whom (26%) had TSH values above the normal range (>2.0 μU/ml). There was no correlation between TSH concentrations and nodularity of goiters. Stimulation with TRH was performed in 52 patients and 39 normal subjects. Patients with basal serum TSH values >0.5 (μU/ml had increases in serum TSH after TRH exceeding those of the controls. However, 1/15 patients with diffuse goiter and 10/37 with nodular goiter had impaired or absent TSH responses to TRH. This finding may be a sign of functional autonomy. The normal subjects and the patients showed the same T3 response to TSH during the TRH test, and the T3 response was significantly correlated with the TSH increase after TRH. This was tentatively interpreted as indicating similar sensitivity to TSH in normal subjects and goitrous patients. However, it is not known whether T3 and growth responsiveness to TSH are associated. It is concluded that goiter development was probably TSH dependent in about one-fourth of the patients. In the majority of cases goiter maintenance and growth seemed not to be TSH dependent at the time of study.