Thyroid Function Tests in Patients on Long‐term Treatment With Various Anticonvulsant Drugs

Abstract

Thyroid function tests were studied in patients undergoing long-term treatment with various anticonvulsant drugs. Previous reports that diphenylhydantoin induces a decrease in the serum concentrations of total and free thyroxine (T4) and triiodothyronine (T3) without a change in the TSH concentration were confirmed. Diphenylhydantoin had no effect on reverse T3. Carbamazepine was also found to decrease serum T4, the free T4 index and T3 but, with the exception of T3, the decrease was smaller than that induced by diphenylhydantoin. Dipropylacetic acid did not influence the serum thyroid hormone concentrations, and neither did primidone. This demonstrates that the interaction between anticonvulsant drugs of different chemical structure and thyroid hormone metabolism is diverse. None of the drugs tested altered serum TSH or the T3 uptake test for the estimation of unsaturated thyroid hormone binding-capacity in serum. These two tests are considered diagnostically more dependable than the measurement of thyroid hormones in serum when diphenylhydantoin and carbamazepine are administered.

Association of antiepileptic drug usage, trace elements and thyroid hormone status

“…In this cohort, it has been shown that TH profiles in subjects without anti-epileptic drugs (AEDs) were comparable with the general population. However, AEDs were strongly associated with decreased T 4 , free T 4 (FT 4 ), T 3 , and rT 3 levels which is in agreement with other studies (24,25,26). It has been speculated that the changed thyroid parameters in patients that use AEDs can be explained by an influence of AEDs on binding proteins (27), a stimulation of hepatic degradation or conjugation of TH (28) or an altered peripheral deiodinase activity (23).…”

“…Due to the observational nature of this study, it is very difficult to draw any conclusions on the causative or mechanistic features of these results. It is very well possible, although speculative, that AEDs interfere with the transport, metabolism, or excretion of trace elements, as is described for TH (23,24,25,26,27,28). Furthermore, although the generalizability of our findings may be limited, it is important to be aware of confounders if Se or Cu levels are analyzed in subjects on commonly prescribed AEDs.…”

A comparative study of thyroid status of patients on phenytoin, carbamazepine and valproate monotherapy

“…28,29 Valproate on the other side showed no significant change in the serum T3, T4 and TSH concentration, this results were in consistent with the other studies reported earlier in contrast other studies found normal thyroid hormone levels while TSH levels were increased. [30][31][32][33][34] This may be due to CBZ and Phenytoin induces hepatic microsomal enzymes markedly in dose-dependent fashion whereas VAL has no significant effect.…”

Thyroid Function in Children with Long-Term Anticonvulsant Treatment

“…Since then, reduced concentrations of serum thyroid hor mones in patients treated with PHT have been reported by several investigators [2][3][4], and the effects of other anticonvulsants on thyroid hormones have also been noted [5][6][7][8].…”