ISSN:
1432-1041
Keywords:
phenytoin
;
thyroid hormones
;
thyroid function tests
;
free thyroxine
;
free triiodothyronine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Medicine
Notes:
Summary Total thyroxine and triiodothyronine levels are often reduced in long-term phenytoin therapy, a finding at variance with the euthyroid clinical state of these subjects. We have measured free (biologically active) thyroid hormone levels in 31 patients on phenytoin therapy and have found a significant reduction in measurements of both free thyroxine and free triiodothyronine. In contrast, addition of phenytoin to normal serum in vitro resulted in an increase in free thyroxine and free triiodothyronine concentrations. The findings in vitro are consistent with displacement of thyroid hormones from thyroxine binding globulin while the reduced free hormone levels in vivo confirm that the effects of phenytoin are not confined to binding inhibition and suggest that phenytoin has induced a change in the cellular metabolism of thyroid hormones.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00543499
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