Hypothyroidism and Phenytoin Intoxication

Excerpt

To the editor: Regarding the recent brief report by Kushnir and colleagues (1), I should like to question the authors' discussion and conclusions. They state that the phenytoin had uncovered "occult primary hypothyroidism" and adduce as evidence an exaggerated thyrotrophin response to a thyrotrophin-releasing hormone test done only 2 weeks after the phenytoin therapy was discontinued. Occult or preclinical primary hypothyroidism usually denotes the findings of a normal thyroxine level and an elevated basal thyrotrophin level in a clinically euthyroid patient (2). This patient's thyrotrophin level had rapidly fallen to within the normal range, making occult disease very unlikely. In