Increased Protein-Bound Iodine and Thyroxine-Binding Globulin in Acute Intermittent Porphyria

Abstract

SOME of the manifestations of acute intermittent porphyria are suggestive of thyrotoxicosis. These include emotional lability, tachycardia and muscular weakness, and such findings have on occasion led to thyroidectomy in acute porphyria.¹ Although the patients are usually euthyroid, as shown by normal thyroidal uptake of radioiodine (RAI) and basal metabolic rate, they may be erroneously considered to have hyperthyroidism because the serum protein-bound iodine (PBI) and thyroxine iodine (total T₄) are frequently increased.² The mechanism for these increases in thyroid hormone levels in the face of apparent euthyroidism has not been elucidated and is the subject of this . . .