DIAGNOSIS OF EQUIVOCAL HYPOTHYROIDISM, USING THYROTROPIC HORMONE (TSH)*†

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Abstract
Thyrotropic hormone (TSH) induces a marked rise of radioiodine (I13l) uptake by the thyroid gland in euthyroidism and pituitary hypothyroidism but not in primary thyroid myxedema. It was used, therefore, in the study of a group of subjects with suspected or equivocal hypothyroidism, to determine whether the thyroid response to TSH could be correlated with the final diagnosis. TSH response was an accurate index in 16 of 17 patients studied. Thyroid medication did not inhibit action of TSH. Repetition after as long as 6 mos. demonstrated that results were reproducible. Since augmentation of I131 uptake may be similar in normal - subjects and in those with pituitary hypothyroidism, the latter diagnosis must be considered as a possible source of diagnostic error. A positive response is, therefore, in these rare instances, of less diagnostic value than a negative response.