Elevation of the Serum Protein-Bound Iodine in Acute Intermittent Porphyria1

Abstract

The mean value of the serum protein-bound iodine (PBI) in 12 patients with acute intermittent porphyria was 8.46 ±.32 (sem) μg/100 ml serum. The difference between this mean and the normal mean was significant to a P value of less than .001 by Student's t-test. Hyperthyroidism could not be demonstrated. There was no evidence of abnormal amounts of circulating iodoproteins, and no evidence of increased binding of thyroxine to serum proteins. The half-life of intravenously administered thyroxin I¹³¹ was prolonged in the 2 patients thus studied, although the thyroxine degradation rate as μg thyroxine per day was normal. Indices of liver function are presented, and it is suggested that the elevation of serum protein-bound iodine in acute intermittent porphyria may be related to a decreased rate of hepatic catabolism of thyroxine.