[Classification of asymptomatic autoimmune thyroiditis by thyrotropin-releasing hormone loading].

Thyrotropin-releasing hormone loading was performed on 91 patients with asymptomatic autoimmune thyroiditis. Four women had no response to this loading test and had high levels in serum total and free thyroxine (TT4, FT4) and in serum total and free triiodothyronine (TT3, FT3). These patients might be classified as subclinical hyperthyroidism (Group G). Twenty-four patients had normal levels of both basal and peak thyrotropin after loading and were classified as Group I. There were no significant differences between 45 controls (Group C) and Group I patients in serum thyroid hormone levels. Patients with normal basal and high peak levels of thyrotropin were included in Group II. The number of patients in this group was 53. The mean levels of basal and peak thyrotropin were 4.8 microU/ml and 39.6 microU/ml, respectively, and were significantly higher than in Group C and Group I (P less than 0.005). In 10 patients classified as Group III with high levels of both basal and peak thyrotropin, serum concentrations of TT4, FT4 and FT3 were significantly lower than in the other groups (P less than 0.025); however, significant differences in TT3 could not be seen among them. Serum cholesterol levels gradually increased from Group C to Group III. There were significant differences between Group C and Group II (P less than 0.05).