[Thyroid function parameters and TSH in patients treated with anticonvulsant drugs]

Area of Science:

• Endocrinology
• Pharmacology
• Neurology

Background:

• Antiepileptic drugs (AEDs) are known to affect thyroid hormone levels through various mechanisms.
• Diphenylhydantoin is a well-documented example of an AED influencing thyroid function.

Purpose of the Study:

• To analyze the effects of long-term monotherapy and combination therapy with common AEDs on serum thyroid hormone levels.
• To compare the impact of different AEDs (phenobarbital, carbamazepine, sodium valproate, diphenylhydantoin) on thyroid hormone profiles.

Main Methods:

• Study included 96 patients undergoing long-term treatment with AEDs.
• Serum levels of T4, free T4 index, T3, reverse T3 (rT3), and TSH were measured.
• Patients were grouped based on the specific AEDs or combinations used.

Main Results:

• A decrease in serum T4 and free T4 index was observed in a significant number of patients.
• Changes were most pronounced with diphenylhydantoin, carbamazepine, and phenobarbital.
• Reverse T3 levels decreased, while T3 and basal TSH levels remained generally normal across all groups.

Conclusions:

• AEDs induce distinct changes in thyroid hormone levels, differing from non-thyroidal illness patterns.
• Basal TSH is a reliable marker for assessing euthyroid status in patients on long-term AED treatment.
• The findings highlight the importance of monitoring thyroid function in patients receiving chronic antiepileptic therapy.