Administration of the anticonvulsant 5,5-diphenylhydantoin sodium (DPH, Dilantin) depresses the level of serum protein-bound iodine (PBI) without inducing clinical hypothyroidism or changing other measures of thyroid function, such as 24-hour thyroidal accumulation of I131, thyroidal clearance of I131, serum cholesterol, and basal metabolic rate (1). Since DPH also induces a fall in the serum P...
