THYROTROPIC ACTIVITY IN THE SERUM OF EUTHYROID, TREATED HYPERTHYROID AND POSTOPERATIVE HYPOTHYROID PATIENTS

Abstract

The bio-assay technique for thyrotropin (TSH) described by Adams and Purves and modified by McKenzie was found to have a sensitivity of 0.02 milliunit of TSH (with an injection volume of 0.5 ml.) and an average index of precision of 0.247. With this technique, TSH was detected in the sera of 16 out of 20 euthyroid subjects (0.084-0.175 mu. per ml.). The daily variation of the serum TSH level in 4 euthyroid subjects was only slight over a period of five days. Most of the thyro -tropic activity (bovine TSH) added in vitro was recovered from the sera of euthyroid subjects and patients with Graves'' disease. A rise in serum TSH concentration was noted at two and four hours after the intramuscular injection of heterologous TSH (10 USP units), with a return to the original level six hours after the injection. The maximal increase in TSH concentration was twofold. In 9 of 10 patients with Graves'' disease, thyroidectomy had little effect on the serum TSH level at twenty-four and forty-eight hours after operation, but at fifteen days there was a slight decrease. By sixty days, there was an increase in serum TSH concentration in the 4 patients (of the original 10) whose sera were re-assayed. There was a delayed response (ten hours) in the thyroid activator determination with the sera of 3 out of 9 thyrotoxic patients; 2 of these 3 patients were taking antithyroid medication.