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Changes of thyroid hormone levels in epileptic patients
1Department of Neurology, Tongji Hospital, Tongji Medical University, Wuhan.
Journal of Tongji Medical University = Tong Ji Yi Ke Da Xue Xue Bao
|January 1, 1994
Summary
Antiepileptic drugs (AEDs), particularly enzyme inducers like phenytoin and carbamazepine, can lower thyroid hormone levels in epilepsy patients. These changes are drug-induced, not caused by epilepsy itself, and do not typically lead to hypothyroidism symptoms.
Area of Science:
- Endocrinology
- Neurology
- Pharmacology
Background:
- Epilepsy is a neurological disorder affecting millions worldwide.
- Thyroid hormone levels can be influenced by various factors, including medications.
- Antiepileptic drugs (AEDs) are crucial for managing epilepsy but may have off-target effects.
Purpose of the Study:
- To investigate the impact of different AEDs on serum thyroid hormone levels in epilepsy patients.
- To differentiate between drug-induced thyroid hormone changes and those related to epilepsy itself.
- To explore the role of enzyme-inducing AEDs in altering thyroid hormone metabolism.
Main Methods:
- Radioimmunoassay was used to measure serum levels of triiodothyronine (T3), thyroxine (T4), free T3 (FT3), free T4 (FT4), and thyrotropin (TSH).
- 150 epilepsy patients were studied, divided into groups receiving single AEDs (Sod valproate, carbamazepine, phenytoin, MixtBrodsky) or no treatment.
- A healthy control group was included for comparison.
Main Results:
- Enzyme-inducing AEDs, specifically phenytoin (PHT) and carbamazepine (CBZ), significantly decreased serum T3, T4, FT3, and FT4 levels compared to controls, untreated patients, and non-enzyme-inducing AED groups.
- No significant differences in thyroid hormone levels were observed between healthy controls, untreated epilepsy patients, and those on non-enzyme-inducing AEDs.
- All patients with subnormal thyroid hormone levels were on enzyme-inducing AEDs, yet none exhibited clinical hypothyroidism symptoms.
- Serum TSH levels remained within normal limits across all groups, suggesting potential interference with the hypothalamic-pituitary-adrenal (HPA) axis.
Conclusions:
- Changes in thyroid hormone levels in epilepsy patients are primarily caused by specific AEDs, not the disease itself.
- Enzyme-inducing AEDs, through the induction of hepatic microsomal enzymes, are the main mechanism behind decreased serum thyroid hormone concentrations.
- Despite decreased thyroid hormone levels, normal TSH suggests AEDs may affect HPA axis function, warranting further investigation.