Long-term treatment of children with epilepsy with valproate or carbamazepine may cause subclinical hypothyroidism

PURPOSE: The aim of the study was to evaluate serum thyroid hormone balance in children receiving long-term therapy with carbamazepine (CBZ), valproate (VPA), and phenobarbital (PB). METHODS: We determined serum levels of triiodothyronine (T3), thyroxine (T4), free thyroxine (FT4), thyroxine-binding globulin (TBG), and thyroid-stimulating hormone (TSH) in 148 healthy children and 141 children with epilepsy who had been receiving CBZ (61 patients), VPA (51 patients), or PB (29 patients) for 12-161 months. In view of TSH values, three categories of subclinical hypothyroidism were considered: I, TSH greater than the control-group mean + 2 SD (4.37 mIU/L in our study) and <6 mIU/L; II, TSH between 6 and 12 mIU/L; and III, TSH >12 mIU/L. RESULTS: In all treated groups, mean T4 and FT4 levels were lower than in the control group, whereas the CBZ- and VPA-treated children additionally showed reduced mean T3 and TBG levels and increased mean TSH levels. In the group receiving CBZ, 8.2% had TSH values higher than the normal-range maximum, by comparison with only 3.6% of healthy children. The increase in TSH levels was particularly marked in VPA-treated children, accounting for 26% of patients with subclinical hypothyroidism. CONCLUSIONS: Our results, in contrast to previous reports, suggest that CBZ and particularly VPA may induce subclinical hypothyroidism. This suggests a need for careful monitoring of TSH levels in children receiving CBZ or VPA.     

Brief Communication: NO EFFECT OF LONG-TERM VALPROATE THERAPY ON THYROID AND PARATHYROID FUNCTIONS IN CHILDREN

In this study, we studied serum calcium, phosphorus, alkaline phosphatase, thyroid hormones (total thyroxine, free thyroxine, thyroid-stimulating hormone), parathyroid hormone, and osteocalcine levels in children with epilepsy who had been receiving long-term valproate (VPA) therapy in order to determine whether there was any effect of VPA therapy on these hormones. The study included 31 patients with epilepsy receiving VPA and 22 healthy age-matched controls. The age ranged from 15 months to 16 years and 18 months to 17 years in the study and control group, respectively. The duration of VPA use was between 12 months and 5 years (1.93 &#45 1.90 years). When comparing the results, we did not find any significant difference in any of the parameters, including serum calcium, phosphorus, alkaline phosphatase, osteocalcine, and thyroid and parathyroid hormone levels, between the study and control group. We suggest that VPA can safely be used with regard to thyroid and parathyroid dysfunction in childhood epilepsy.     

No effect of long-term valproate therapy on thyroid and parathyroid functions in children

In this study, we studied serum calcium, phosphorus, alkaline phosphatase, thyroid hormones (total thyroxine, free thyroxine, thyroid-stimulating hormone), parathyroid hormone, and osteocalcine levels in children with epilepsy who had been receiving long-term valproate (VPA) therapy in order to determine whether there was any effect of VPA therapy on these hormones. The study included 31 patients with epilepsy receiving VPA and 22 healthy age-matched controls. The age ranged from 15 months to 16 years and 18 months to 17 years in the study and control group, respectively. The duration of VPA use was between 12 months and 5 years (1.93 +/- 1.90 years). When comparing the results, we did not find any significant difference in any of the parameters, including serum calcium, phosphorus, alkaline phosphatase, osteocalcine, and thyroid and parathyroid hormone levels, between the study and control group. We suggest that VPA can safely be used with regard to thyroid and parathyroid dysfunction in childhood epilepsy.     

Brief Communication: EVALUATION OF THYROID AND PARATHYROID FUNCTIONS IN CHILDREN RECEIVING LONG-TERM CARBAMAZEPINE THERAPY

We studied serum calcium, phosphorus, alkaline phosphatase (ALP), thyroid hormones (total thyroxine [TT4], free thyroxine [FT4], thyroid-stimulating hormone [TSH]), parathyroid hormone (PH), and osteocalcine levels in children with epilepsy who had been receiving long-term carbamazepine (CBZ) therapy to determine whether there was any effect of CBZ therapy on these hormones. The study included 18 patients with epilepsy receiving CBZ and 16 healthy age-matched controls. The age ranged from 4-18 years (11.26 &#45 3.59 years) and 4.5-17 years (11.16 &#45 3.13 years) in the study and control group, respectively. The duration of CBZ use was between 10 months-5 years (3.12 &#45 1.09 years). When comparing the results we did not find any significant difference in serum calcium, phosphorus, ALP, osteocalcine and TSH and PH levels between the groups (p >. 05). However, serum TT4 and FT4 levels were found to be significantly lower in the study group than those of control group (p <. 05). However, we observed no clinical signs of hypothyroidism in all subjects. To these findings we suggest that serum thyroid hormone levels should be monitored in children receiving long-term CBZ therapy.­­     

Evaluation of thyroid and parathyroid functions in children receiving long-term carbamazepine therapy

We studied serum calcium, phosphorus, alkaline phosphatase (ALP), thyroid hormones (total thyroxine [TT4], free thyroxine [FT4], thyroid-stimulating hormone [TSH]), parathyroid hormone (PH), and osteocalcine levels in children with epilepsy who had been receiving long-term carbamazepine (CBZ) therapy to determine whether there was any effect of CBZ therapy on these hormones. The study included 18 patients with epilepsy receiving CBZ and 16 healthy age-matched controls. The age ranged from 4-18 years (11.26 +/- 3.59 years) and 4.5-17 years (11.16 +/- 3.13 years) in the study and control group, respectively. The duration of CBZ use was between 10 months-5 years (3.12 +/- 1.09 years). When comparing the results we did not find any significant difference in serum calcium, phosphorus, ALP, osteocalcine and TSH and PH levels between the groups (p >.05). However, serum TT4 and FT4 levels were found to be significantly lower in the study group than those of control group (p <.05). However, we observed no clinical signs of hypothyroidism in all subjects. To these findings we suggest that serum thyroid hormone levels should be monitored in children receiving long-term CBZ therapy.     

The effect of antiepileptic drug therapy on antioxidant enzyme activity and serum lipid peroxidation in young patients with epilepsy

Changes in antioxidant defense mechanisms and the resulting increased lipid peroxidation are involved in the pathogenesis of epilepsy. Research findings concerning the effect of antiepileptic therapies on these processes are discordant. The aim of our study was to estimate, firstly, the activity of the following antioxidant enzymes: superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione reductase (GSSG-R), and secondly, malondialdehyde (MDA) serum concentration in children and adolescents newly diagnosed with epilepsy and receiving either carbamazepine (CBZ) or valproate (VPA) monotherapy, or polytherapy. The study group included 90 young patients with epilepsy, aged 6 months to 20 years. In 22 patients epilepsy was newly diagnosed; CBZ monotherapy was administered to 16 patients, VPA monotherapy--to 25, and polytherapy--in 27 cases. The control group consisted of 61 non-epileptic patients aged 4-17 years. SOD, GSH-Px and GSSG-R activities and MDA concentration were measured using spectrophotometry. SOD activity was decreased in newly diagnosed epileptic children receiving VPA or CBZ monotherapy (p < 0.05), or polytherapy (p < 0.01) in comparison to relevant levels in non-epileptic patients. GSH-Px activity was increased in all the patients, but significantly in those receiving polytherapy (p < 0.05). While in patients newly diagnosed with epilepsy no change in GSSG-R activity was found, its level was slightly lower both in those receiving VPA monotherapy and polytherapy, but increased in those with CBZ monotherapy. MDA concentration was elevated in all the epileptic patients, significantly (p < 0.05) both in VPA monotherapy and in polytherapy, while insignificantly--in newly diagnosed epilepsy and in CBZ monotherapy. Our results indicate that in the serum of children and adolescents with epilepsy the oxidants-antioxidants balance is modified by antiepileptic therapy.     

Thyroid and Myocardial Function After Replacement of Carbamazepine by Oxcarbazepine

Summary: We determined changes in serum concentrations of thyroid hormones during carbamazepine (CBZ) therapy during a 5-year prospective follow-up study of 20 patients with newly diagnosed epilepsy. In addition, we evaluated the effects of replacing CBZ with oxcarbazepine (OCBZ) in 12 male patients with epilepsy in a 6-month prospective follow-up study. Circulating thyroxine and free thyroxine levels decreased after 2-month CBZ treatment and remained at a low level during the 5-year follow-up. There were no associated changes in serum thyrotropin (TSH) concentrations. When CBZ was replaced by OCBZ, the function of the liver's P450 enzyme system normalized, as shown by an increase in antipyrine_T1/2, and a decrease in antipyrine_CL. Serum total and free thyroxine levels increased, and thereafter serum TSH levels decreased. Indexes of diastolic heart function improved concomitantly, which may reflect subclinical hypothyroidism at the cellular level during CBZ treatment. We conclude that normal thyroid function can be restored in patients with epilepsy by replacing CBZ with OCBZ.     

Thyroid function in girls with epilepsy with carbamazepine, oxcarbazepine, or valproate monotherapy and after withdrawal of medication

Summary: Purpose: Antiepileptic drugs may affect the serum thyroid hormone concentrations. The aim of this study was to evaluate thyroid function in 78 girls taking carbamazepine (CBZ), oxcarbazepine (OXC), or valproate (VPA) monotherapy for epilepsy and after withdrawal of the treatment. Methods: Forty‐one girls taking VPA, 19 taking CBZ, and 18 taking OXC for epilepsy, as well as 54 healthy age‐matched controls, aged 8 to 18 years, participated in the study. All the girls were examined clinically, and their pubertal stage was assessed. Blood samples were obtained for thyroid hormone and antibody assays. These examinations were repeated after a mean follow‐up of 5.8 years to assess thyroid function, and 64 (82%) of 78 patients and 42 (78%) of 54 controls agreed to participate in the second evaluation. Results: In the first evaluation, the mean serum thyroid hormone concentrations were lower in the girls taking CBZ [thyroxine (T₄), 70.2; SD, 10.9 nM; and free thyroxine (FT₄), 11.5; SD, 1.8 pM] or OXC (T₄, 74.9; SD, 16.4 nM; and FT₄, 11.3; SD, 1.8 pM) than in the control girls (T₄, 96.6; SD, 15.1 nM, and FT₄, 14.4; SD, 1.5 pM; p < 0.001, all comparisons). However, thyrotropin (TSH) concentrations were normal in the girls taking CBZ or OXC. Sixty‐three% of the girls taking CBZ and 67% of the girls taking OXC had serum T₄ and/or FT₄ levels below the lower limit of the reference range. The VPA‐treated girls with epilepsy had normal serum T₄ and FT₄ concentrations, but slightly increased TSH levels (3.3; SD, 1.5 mU/L; p < 0.01) compared with the control girls (2.5; SD, 1.0 mU/L). Normal serum hormone concentrations were restored in the patients who discontinued the medication. Conclusions: Both CBZ and OXC reduce serum thyroid hormone concentrations in girls with epilepsy. Conversely, VPA is associated with normal serum thyroid hormone and increased thyrotropin levels. However, our results suggest that the changes in serum thyroid hormone and thyrotropin levels are reversible after withdrawal of the medication.     

Growth and lipid metabolism in girls and young women with epilepsy during pubertal maturation

Summary:  Purpose: To assess growth and the serum lipid profile in girls with epilepsy receiving monotherapy at a mean age of 12.6 years and approximately 6 years later.
Methods: A population-based cohort of 77 girls with epilepsy and 49 healthy controls participated in this follow-up study including two cross-sectional evaluations (age range, 8–18.5 years on the first evaluation, and 12.5–25.8 years on the second evaluation). Forty of the patients were initially taking valproate (VPA), 19, carbamazepine (CBZ), and 18, oxcarbazepine (OXC). Growth data were compiled, body mass index (BMI) was calculated, and serum total (TC), and high-density lipoprotein (HDL-C) and low-density lipoprotein (LDL-C) cholesterol and triglyceride concentrations were analyzed.
Results: Linear growth and final height did not differ between the patients and the controls. At follow-up, the mean BMI of the patients who were off medication (61%) was similar to that of the controls, whereas the patients initially treated with VPA who were still taking any medication had a higher BMI. On the first evaluation, the patients taking VPA had low serum HDL-C, and those taking CBZ or OXC had high serum TC and LDL-C concentrations. At follow-up, serum lipid levels were similar in the patients off medication and the controls.
Conclusions: Neither epilepsy nor antiepileptic therapy affects linear growth or final height, but they may have unfavorable effects on body weight and serum lipid concentrations. Lipid-profile impairment seems to be transient if the medication is discontinued. Overweight is common in patients treated with VPA during puberty if epilepsy and medication continue into adulthood.     

Thyroid hormones in children on antiepileptic therapy

The aim of this study was to evaluate the thyroid function alterations in a group of epileptic children taking antiepileptic drugs (AEDs). Patients demographic data and the free throxine (fT4) and thyroid-stimulating hormone (TSH) levels at the beginning of the treatment and at the third, sixth and ninth months of AED treatment were recorded retrospectively. A total of 106 children, 59 males and 47 females, were enrolled in the study. Mean patient age was 3.7 years, ranging between 3 months and 14 years. In total, 54% of patients were on valproic acid (VPA), 16% phenobarbital (PB), 14% were on carbamazepine (CBZ), 6% were on oxcarbazepine (OXC), 5% were on levetiracetam, and 5% were on topiramate therapy. There were no significant differences in average fT4 values between the drug groups. But the mean fT4 levels of the patients on VPA therapy showed a clear decrease within the observation period. No significant difference in average TSH values between the groups was detected in the beginning and in the third and sixth month. However, in the ninth month, a significant increase in TSH values was found in the VPA group (p = 0.007). In the patients taking VPA, average TSH values rose progressively while staying within normal limits. During follow-up, thyroid dysfunction were found in 21 patients (19.6%). A statistically significant relationship was found between severe electroencephalography (EEG) findings and thyroid dysfunction (p = 0.041). It was concluded that epileptic children with severe EEG findings and using VPA could have thyroid dysfunction. These patients should be followed up closely by thyroid function tests during treatment.     

Serum lipids,vitamin B12 and folic acid levels in children receiving long-term valproate therapy

In this study, serum triglyceride, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), vitamin B12 and folic acid levels were studied in children with epilepsy who had been receiving long-term valproate (VPA) therapy. Our purpose was to determine that whether or not there was any affect of VPA therapy on serum lipids, vitamin B12 and folic acid levels. The study includes 26 patients (13 males, 13 females) with epilepsy who had been receiving long-term VPA therapy and in 28 healthy children (14 males, 14 females). The age ranged from 14 months-12 years (8.22 +/- 3.64 years) and 9 months-18 years (8.97 +/- 4.85 years) in the study and control group, respectively. Because serum lipid ranges may be changed according to the age groups in childhood, the children were divided into three groups as follows; younger than < 5 years, between 5-10 years, and older than > 10 years. The duration of VPA use was between 10 months and 7 years (1.83 +/- 1.80 years). Serum VPA level changed between 42-108 micrograms/ml (75.09 +/- 21.42 micrograms/ml). When comparing the results we did not find any significant difference in all parameters including lipid profiles, vitamin B12 and folic acid levels between the groups (P > 0.05). Additionally, we did not find any correlation between lipid profile and age at start of therapy, duration of therapy, serum VPA level (P > 0.05). In conclusion, our findings showed that VPA therapy did not change serum lipids, vitamin B12 and folic acid concentrations; therefore, we suggest that VPA may be safely used with regard to lipid composition, vitamin B12 and folic acid levels in childhood epilepsy.     

Evaluation of subclinical hypothyroidism in ambulatory children with controlled epilepsy on valproate monotherapy

There are conflicting reports in the literature about the influence of valproate on thyroid function. A cross-sectional study was performed to determine the prevalence of subclinical hypothyroidism in ambulatory children aged 3 to 15 years with controlled epilepsy receiving valproate monotherapy for at least 6 months. Fifty-seven consecutive children with controlled epilepsy on valproate monotherapy and 52 healthy age- and sex-matched control children were studied. Thyroid-stimulating hormone, free thyroxine, antithyroid peroxidase antibodies, and serum valproic acid levels were measured. There was a significantly high (P = .012) prevalence of subclinical hypothyroidism (26%) in those receiving valproate monotherapy compared with healthy controls (7.7%). Median duration of valproate therapy was significantly higher (P = .039) in the subclinical hypothyroidism group (21 months, range 6-36) compared with those without subclinical hypothyroidism (14 months, range 6-25). Results of the present study suggest higher prevalence of subclinical hypothyroidism in children with controlled epilepsy on long-term valproate monotherapy.     

Valproic acid and thrombocytopenia in children: A case-controlled retrospective study

Thrombocytopenia in association with valproic acid (VPA) therapy has been reported in patients of various ages with incidences ranging from 1 to 32%. To evaluate this association in a pediatric population, we retrospectively studied 167 children treated with VPA at our institution between 1989 and 1993. Ninety-one patients on VPA monotherapy and 76 on VPA polytheraphy (VPA plus 1 to 3 other antiepileptic drugs) were compared with 92 age- and sex-matched control patients treated with antiepileptic drugs other than VPA. Study variables included patient age, most recent platelet count, VPA dose, dose/kg, and serum VPA level. Thrombocytopenia, defined as a platelet count <200 × 10³/mm³, was present in 21.6% of the children treated with VPA (26.4% in those on VPA monotherapy and 15.8% in those on VPA polytherapy) but in only 5.4% of controls untreated with VPA. Serum VPA level was the highest risk factor for the development of thrombocytopenia in these patients (P = .0001) and greater age also independently predicted thrombocytopenia. The dose of VPA or dose/kg were not independent predictors of thrombocytopenia (P = .0025). The degree of thrombocytopenia was mild among these patients, reflected in the absence of significant difference in mean platelet count between the three groups and the absence of any bleeding complication or excessive bruising. We conclude from these findings that the risk for children developing severe thrombocytopenia with bleeding complications while taking VPA is low and that mild thrombocytopenia does not necessarily mandate discontinuing the drug. Because higher serum VPA levels do predict thrombocytopenia, platelet counts should be closely monitored after dose escalation in such patients.     

Valproate sodium enhances body weight gain in patients with childhood epilepsy: a pathogenic mechanisms and open-label clinical trial of behavior therapy

ObjectivesExcessive weight gain associated with valproate sodium (VPA) may predispose patients with epilepsy to other health problems such as insulin resistance. The purpose of this study was to examine the changes in body weight and several biochemical parameters in children receiving VPA treatment. The effects of behavior therapy for epileptic children with VPA-induced weight gain are discussed.MethodsFifteen patients newly diagnosed with epilepsy were included in the study. The following parameters were measured: body weight, body mass index (BMI), serum glucose, serum insulin, serum VPA concentration and serum free carnitine. In addition, behavior therapy was introduced at the initiation of VPA therapy, and lasted at least for 2 years.ResultsAfter 6 months of follow-up, there were eight (53%) patients in whom weight gain was demonstrated. Significant increases in the serum insulin level and the insulin/glucose ratio were observed in the weight gain group (p < 0.01). All patients with significant weight gain showed increased appetite. However, BMI stopped increasing with intensive behavior therapy.ConclusionsThese findings suggest that an increase in serum insulin and insulin/glucose levels may cause weight gain, possibly by stimulating appetite, and that weight changes seem to be reversible with intensive behavior therapy without discontinuation of VPA.     

The effects on lipid and apolipoprotein serum levels of long-term carbamazepine, valproic acid and phenobarbital therapy in children with epilepsy

The aim of the present study was to assess the effect of long-term carbamazepine (CBZ), valproic acid (VPA) and phenobarbital (PB) treatment on serum lipids and apolipoproteins in epileptic children. Serum levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C) and triglycerides (TGs) were measured and the LDL-C/HDL-C and TC/HDL-C ratios were calculated in 320 children and adolescents (129 receiving CBZ, 127 receiving VPA and 64 receiving PB) suffering from various types of epilepsy. Additionally, in a subgroup of 181 children (68 CBZ; 78 VPA; 35 PB) apolipoprotein A-I (apoA-I), apolipoprotein B (apoB), HDL2-C and HDL3-C were measured and apoA-I/apoB and HDL2-C/HDL3-C ratios were calculated. Results of the measurements were compared with those of 169 age-and sex-matched healthy controls. None of the variables considered was significantly correlated with time elapsed since start of treatment or with drug concentration in serum. TC and LDL-C serum levels were high in children receiving CBZ or PB and low in those treated with VPA. Serum LDL-C level exceeded 130 mg/dl in 27.9% of CBZ-group, 31.8% of the subjects receiving PB, but only in 7% of those receiving VPA and in 11.8% of control group subjects. CBZ-treated children also showed high HDL-C and HDL3-C values. In the group receiving VPA, HDL2-C, HDL2-C/HDL3-C ratio and apo B were significantly lower than in the control group. Mean apoA-I levels were low in all treated groups: by contrast, in neither group did TGs, VLDL-C levels and TC/HDL-C or LDL-C/HDL-C ratios differ significantly from the corresponding control group. Our results suggest that the effects of long-term AED therapy on lipid profile and, particularly, on apolipoprotein serum levels increase risk of atherosclerosis-related disease. Moreover, these results confirm our previously reported increased risk in CBZ and PB-treated patients.     

A case of phenytoin intoxication induced by hypothyroidism

A 42-year-old woman who presented phenytoin intoxication induced by acute hypothyroidism was reported. She had a 29-year history of hypothyroidism and a 18-year history of epilepsy. She was treated with phenytoin (PHT) 100 mg, mephobarbital (MPB) 200 mg, valproic acid (VPA) 400 mg and thyroid powder 100 mg daily for 2 years. She had no medical problem until she noticed gait disturbance and diplopia which appeared 1 month after sudden withdrawal of thyroid powder. On admission, she was somnolent and somewhat disoriented. She had nystagmus in horizontal direction of gaze. Her speech was slurred and she could not sit nor stand due to trunkal ataxia. There was prominent intentional tremor in finger-nose test and heel-shin test showed severe ataxia. Blood cell count and blood chemistry examinations were normal. Serum PHT, phenobarbital (PB) levels were elevated as to 26.4, 36.4 micrograms/ml, respectively. VPA level was low. The endocrinological examinations revealed primary hypothyroidism. EEG showed generalized slow background, but cranial MRI, EMG, SEP and ECG were normal. Thyroxine (T4) administration was started soon, and in the course of thyroid hormone replacement, her cerebellar symptoms gradually improved and serum PHT level decreased even to the subtherapeutical level with the same amount of antiepileptic drugs treatment. By the 40th day of admission, thyroid function became normal and cerebellar signs disappeared, however, she needed 200 mg PHT daily to obtain good control of epilepsy. Cerebellar symptoms of this patient were thought to be PHT intoxication rather than ataxia caused by hypothyroidism itself from the viewpoint of clinical manifestations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thyroid hormones in epileptic children receiving carbamazepine and valproic acid

Carbamazepine and valproic acid are effective antiepileptic drugs for treating many types of epilepsy. Although they are well tolerated, many effects on endocrine function have been reported. Changes in serum thyroid hormones levels in 37 children with epilepsy during carbamazepine and valproic acid therapy were analyzed, and the thyroid hormone concentration after thyrotropin-releasing hormone test was evaluated. Serum thyroxine and free thyroxine levels were significantly lower in patients treated with carbamazepine and carbamazepine plus valproic acid than in the control subjects; serum thyroxine and free thyroxine concentrations were unaffected by valproic acid monotherapy. Serum triiodothyronine and free triiodothyronine concentrations were similar in the three groups of patients studied. Thyroid-stimulating hormone serum levels were normal in all patients, and the thyrotropin responses to the thyrotropin-releasing hormone were similar to control group. Our data suggest that children treated with carbamazepine may have subclinical signs of hypothyroidism, and these changes are more evident if carbamazepine is given in association with valproic acid, while no alteration in thyroid hormones can be found with valproic acid monotherapy. Thyroid-stimulating hormone and thyrotropin-releasing hormone levels do not seem to be affected by these drugs, suggesting that hypothalamic function is not affected in these children.     

Thyroid function in severely disabled children]

Thyroid function tests were studied in 105 severely disabled children. Fifty-four cases (53%) showed following abnormalities. Serum TSH concentration was increased in 2 cases. Both serum T4 and T3 levels were decreased in 18 cases (17%). Only the serum T4 level was decreased in 25 cases (24%). Only the serum T3 level was decreased in 10 cases (9.5%). Two patients showed primary hypothyroidism. Two patients (monozygotic twins) were suspected to have subclinical hypothalamic-pituitary hypothyroidism caused by septo-optic-dysplasia. Abnormal thyroid functions were caused by anticonvulsants in most patients. The serum T4 level was correlated with the number of anticonvulsants, but not correlated with motor performance (daily activity) or feeding function. Four patients who had low T4 level or low T4 and T3 levels were received L-thyroxine supplementation, but no clinical improvement was observed. The serum TSH concentration was decreased and the TRH test showed hyporeaction in all of these cases. The low T3 level and normal T4 level were not related to anticonvulsant administration. Two of these patients were in poor nutritional condition, resulting in so called low T3 syndrome.     

Thyroid Function with Antiepileptic Drugs

Serum thyroid hormone balance was assessed in 108 patients receiving chronic antiepileptic drug (AED) therapy. Forty-five patients were receiving carbamazepine (CBZ), 26 phenytoin (PHT), 16 CBZ-PHT, 11 valproate (VPA), and 10 CBZ-VPA. Serum thyroxine (T4) and free thyroxine (FT4) concentrations were low in patient groups receiving CBZ and/or PHT. Serum T4 concentrations were below the normal range in 24 (53.3%) CBZ patients, 11 (42.3%) PHT patients, 12 (75%) CBZ-PHT patients, and in all 10 patients (100%) receiving CBZ-VPA. Furthermore, serum levels of FT4 were below the normal range in 13 (28.9%) CBZ patients, 6 PHT (23.1%) patients, 5 (31.3%) CBZ-PHT patients, and 5 (50%) CBZ-VPA patients. Despite the decreased serum T4 and FT4 levels in these patients, serum basal and stimulated thyrotropin (TSH) concentrations were normal, except for the slightly increased basal TSH in the CBZ-VPA group. In the VPA group, the findings were different from those in other patients: T4 serum levels were unchanged and FT4, T3, and basal TSH levels increased, but stimulated TSH levels did not differ from those of the control group. The decrease in serum thyroid hormone levels during CBZ and/or PHT medication probably is caused by an accelerated hepatic plasma clearance of these hormones due to induction of hepatic microsomal enzyme systems by these AEDs. VPA, an AED with no liver enzyme-inducing properties, does not cause similar changes. The feedback mechanism is not activated, possibly because of a hypothalamic interference by CBZ and PHT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reduction of steady-state valproate levels by other antiepileptic drugs

Steady-state plasma valproate (VPA) levels were analyzed in 37 children after 6 weeks of VPA therapy. Twenty-six patients were receiving other antiepileptic drugs in addition to VPA (experimental group). Eleven patients who received VPA alone served as controls. The mean VPA dose was not statistically different for the two groups (experimental group, 35.4 mg/kg/day, 11.6 SD; control group, 31.1 mg/kg/day, SD 6.6) The mean plasma VPA level was significantly lower for the experimental group (63.0 micrograms/ml, SD 21.8) than for the control (99.3 micrograms/ml), SD 23.3) (p less than 0.01). VPA level: dose ratio (LDR) was also reduced in the experimental group (1.92, SD 0.75) as compared to controls (3.26, SD 0.65) (p less than 0.01). Within the experimental group the VPA levels and VPA LDR were significantly reduced in patients receiving either phenytoin or phenobarbital. The data suggest that other antiepileptic drugs significantly alter the steady-state level to dose relationship for VPA.