Serum total and free thyroid hormones, reverse T3 (rT3), thyroxin bind
ing globulin (TBG) and thyroid stimulating hormone (TSH) concentration
s were measured in 35 epileptic patients receiving anticonvulsants (ph
enobarbitone, phenytoin). There was a significant reduction found in t
otal thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT
3), free triiodothyronine (FT3) and rT3 in the group treated with, phe
nytoin. The thyroid hormone levels were within normal limits in the gr
oup receiving phenobarbitone.