Estimation of Serum Thyrotropin (Tsh) and Stimulation With Thyrotropin‐releasing Hormone (Trh) in Thyroid Diseases

Serum TSH has been estimated using a radioimmunological method in 128 controls: 1.9±1.7 μU/mI (mean ±S.D.), in 97 hyperthyroid patients: 1.5± 1.5 μU/ml, and in 40 patients with primary hypothyroidism: 116±72 μU/ml. After stimulation with 200 μg TRH i.v. a positive response (A TSH>2.0 μU/ ml) was found in 58 of 60 controls but only in one of 56 hyperthyroid patients. In 23 hypothyroid patients examined with the TRH test an exaggerated TSH response was found. Four clinical euthyroid patients with Hashimoto thyroiditis had moderately elevated serum TSH and an increased response to TRH, whereas 9 euthyroid patients with diffuse goitre did not differ from the control group. During antithyroid treatment of 66 patients serum TSH was elevated only in half of the patients with subnormal serum thyroxine and normal in almost all cases with normal serum thyroxine. In 34 patients with primary hypothyroidism treated with 1‐thyroxine serum TSH was elevated in all with subnormal serum thyroxine and was not normalized until serum thyroxine levels were within the upper part of normal range. Estimation of serum TSH is of major diagnostic value in primary hypothyroidism and a valuable aid in the control of treatment of hypo‐ and hyperthyroidism. The TRH stimulation test is of value in the diagnosis of hyperthyroidism.