FAMILIAL INCREASE IN THE THYROXINE-BINDING SITES IN SERUM ALPHA GLOBULIN*

Abstract

Thyroxine in human serum migrates during pa- per electrophoresis at pH 8.6 with at least three protein components: an a globulin intermediate be- tween a1 and a2, thyroxine-binding protein (TBP) (1, 2), albumin (1, 2) and a component moving faster than albumin, prealbumin or thyroxinebinding prealbumin (TBPA) (3). Alterations in serum protein-bound iodine (PBI) may occur in certain circumstances without concomitant hyperor hypothyroidism, but with parallel changes in the thyroxine-binding capacity of TBP. Examples are the elevated PBI and TBP capacity in preg- nancy (4, 5) and after estrogen therapy (6), and the depressed PBI and TBP capacity produced by methyl testosterone (7). It seemed logical, there- fore, to look for alterations in TBP in patients with abnormal serum PBI levels in whom other evidence of thyroid dysfunction was lacking. We wish to report the occurrence of an elevated PBI and TBP capacity in an otherwise normal adult male and in one of his three children. CASE REPORT AND METHODS W.W. was a male 48 years of age when seen on March 17, 1958, because his serum PBI was found to be "ele- vated" on a routine periodic health examination. He was asymptomatic and gave no history of thyroid disease in himself or in his family. He had never received radio- graphic contrast media and there was no known ingestion of other organic iodine compounds. He gave no history of diseases known to alter the serum proteins. His libido and potentia were considered to be normal. His physical examination was completely nor- mal. No goiter or evidence of hyper-or hypothyroidism was evident. Hair growth and distribution and genitalia were normal.