Two groups of patients are described and compared, each of whom presented with symptoms and signs referable to the cardiovascular system, generally without thyroid gland enlargement, and who were found to have abnormal thyroid function studies.
In the first group (I), thyroid 131I uptake, labeled triiodothyronine resin uptake, and serum protein-bound iodine estimations were in the hyperthyroid range and were therefore examples of masked hyperthyroidism, but in the second group (II) only the protein-bound iodine level was raised.
The clinical characteristics and hyperthyroid "index scores" were compared and the response to treatment described.
The possible causes of the raised protein-bound