THE USE OF THYROTROPIC HORMONE (TSH) IN THE DIAGNOSIS OF MYXEDEMA*†

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Abstract
Patients with known primary thyroid myxedema, pituitary myxedema and normal thyroid function were evaluated with a BMR, serum cholesterol and radioactive iodine tracer. It was noted that patients with primary thyroid myxedema had BMRs which were, on the avg., lower than those of the pituitary myxedema group, and their cholesterols were generally higher. The avg. I131 tracer of patients with pituitary myxedema was higher than that of the primary thyroid group and was, in fact, in the low normal range. After the admn. of 3 consecutive daily injections of 30 mgm. of Armour''s thyrotropic hormone, the iodine tracers of the primary thyroid myxedema group did not change, whereas there was a marked increase in the uptake of radioactive iodine by the thyroid glands in both the pituitary myxedema and euthyroid patients. Although the increment of increase of the pituitary myxedema patients was greater than in the controls, the final level in both these groups was almost identical. This suggests that the thyroid gland is capable of a maximal response when stimulated with a given dose of TSH. It was shown that this test was repeatable in the same patients and that it was not influenced by the admn. of 1 g. of thyroid a day. The authors suggest that TSH, in association with I131 uptake studies, is a simple technique for distinguishing cases of thyroid and pituitary myxedema. A group of patients whose primary diagnoses were in doubt were studied in this fashion.