Effects of antiepileptic drugs on thyroid hormone function in epilepsy patients

Sex Differences in Adverse Effects of Antiseizure Medications in Adults with Epilepsy: A Systematic Review

BACKGROUND

Sex differences in epilepsy have been described in prevalence, seizure propensity and response to treatment. Therefore, taking into account sex-based differences in epilepsy is important for both diagnostic purposes and therapeutic considerations. However, little is known about sex differences in adverse effects of antiseizure medications (ASMs).

OBJECTIVES

We performed a systematic review searching for sex differences in adverse effects of ASMs in adult persons with epilepsy (PWE) as part of a wider project aimed to assess sex-based differences in efficacy and adverse effects of ASMs in PWE.

METHODS

We conducted a comprehensive literature search in the PubMed database. The search was conducted with no restriction on publication date, and all results up to April 2020 were included. We included articles written in English, Italian, Spanish, or French that evaluated adverse effects of one or more ASMs in PWE, with specific mention of the two sexes. When appropriate, Newcastle-Ottawa or Jadad scales were used to assess study quality.

RESULTS

Of 5164 identified studies, only 167 considered sex in the analysis and were therefore included. Significant sex-related differences were found in 58 of those studies. We found a consistently higher frequency of cutaneous adverse effects in females; higher risk of developing general adverse effects on different ASMs in females; stronger risk of adverse effects on bone metabolism in females, mainly on treatment with enzyme-inducing ASMs; a concordant higher risk of visual field loss was noted in males on vigabatrin; an overall worse lipid profile in males; as well as higher leptin levels and higher body mass index in females treated with various ASMs.

CONCLUSIONS

Our analysis has identified some important sex differences in the adverse effects of ASMs. Clinicians should be aware of these differences when informing patients about the risks associated with ASM treatment in PWE.

Thyroid functions as a parameter in monitoring of antiepileptic drugs

INTRODUCTION

Epilepsy is a chronic neurological disorder that is treated with multiple medications that can have significant side effects. This study investigated the potential effects of antiepileptic drugs on thyroid function.

METHODS

The participants in this study were epileptic adults who had been consistently monitored in follow-up care. The effects of antiepileptic drugs on the serum levels of the thyroid stimulating hormone (TSH), free T3 (fT3), and free T4 (fT4) of these patients were investigated retrospectively by comparing laboratory recordings in three defined periods: prior to antiepileptic drug treatment, between 6 months and 1 year of treatment (early stage), and after 1 year of treatment (late stage).

RESULTS

  A total of 300 epileptic patients (F/M: 175/125) were included in the study. Significant differences in TSH and fT4 serum levels in the late stage compared to the pre-treatment stage (p = 0.006 and p = 0.0005, respectively) were found. TSH values in the late stage of treatment were abnormally high in one case and low in five cases; all six of these cases had normal pre-treatment and early-stage TSH values. Patients who received monotherapy with valproic acid, levetiracetam or carbamazepine were evaluated separately and there was no statistically significant difference in TSH and fT3 levels, while fT4 levels were significantly increased during treatment in each treatment group.

CONCLUSIONS

A significant increase in TSH levels was found in epileptic patients on polytherapy. Our results give us the opportunity to highlight the potential unique or cumulative effect of antiepileptic drugs on thyroid hormone levels.

Significant Association of Antiepileptic Drug Polytherapy with Decreased FT4 Levels in Epileptic Patients

Epileptic patients have to continue anti-epileptic drugs (AED) over a long period of time which can have deleterious effects on the endocrine system including the thyroid hormones with rare check. Risk factors for the development of thyroid dysfunction are still unclear. Therefore the aim of study was to evaluate thyroid functions in epileptic patients receiving anti-epileptic drugs (AED) as monotherapy and polytherapy and to determine potential risk of low thyroid function in epileptic patients receiving treatment. This cross-sectional study included 100 epilepsy patients more than 12 years of age. Serum levels of free thyroxin (FT4), free triiodothyronine (FT3), and thyroid stimulating hormone (TSH) were evaluated in all subjects in addition to serum AED levels. TSH levels were found to be significantly higher in the polytherapy subgroup (p < 0.05) in comparison to the monotherapy group. 44% of the patients in the VPA monotherapy group had raised TSH levels and 41.2% of the patients on CBZ had low FT4. A significant negative correlation was observed between CBZ and FT4 (p < 0.05). Female sex and old age were additional risk factors detected for deranged thyroid function. Female patients with epilepsy, an older age and AED polytherapy were found to be associated with a higher risk of thyroid dysfunction. Thus, Thyroid function in these patients should be monitored closely. In conclusion, we observed significant changes in thyroid hormone levels in patients receiving antiepileptic treatment in both monotherapy and polytherapy. Elevated CBZ levels were significantly associated with decreased FT4 levels.

Is the prevalence of thyroid disease higher in children receiving antiepileptic medication? A systematic review and meta-analysis

PURPOSE

Antiseizure medications (ASM) have long been examined for their potential to induce thyroid dysfunction. The aim of this systematic review and meta-analysis was to assess the prevalence of thyroid disease in children up to 16 years receiving monotherapy with valproate (VPA), carbamazepine (CBZ) and levetiracetam (LEV).

METHODS

PubMed/MEDLINE, Cochrane/CENTRAL databases and the gray literature were searched to identify observational studies providing the prevalence of thyroid dysfunction in the target population under VPA, CBZ, or LEV monotherapy schemes. The results were pooled using a random-effects model, and additional subgroup analyses were performed for the three ASM groups.

RESULTS

Fifteen and thirteen studies met inclusion criteria for the qualitative and the quantitative analysis, respectively, with a total of 945 pediatric patients with prevalence data. Only VPA and CBZ were associated with thyroid dysfunction. The overall prevalence of thyroid abnormality was higher in children receiving ASM [odds ratio (OR) 6.82, 95% confidence interval (CI) 3.96-11.75]. In the subgroup analysis, the prevalence of biochemical thyroid abnormality with increased TSH was higher in the VPA (OR 9.54, 95%CI 5.25-17.34) and the CBZ group (OR 4.08, 95%CI 1.84-9.04) compared with controls.

CONCLUSION

This study confirms the higher prevalence of biochemical thyroid abnormality in children under VPA and CBZ monotherapy, whereas no such evidence is present for LEV. In children with a predisposition for thyroid disease, LEV should be considered over VPA and CBZ, if appropriate for seizure type and epilepsy syndrome. More studies are needed to reach a consensus on monitoring and management of thyroid dysfunction in children receiving ASM therapy.

Antiseizure medications and thyroid hormone homeostasis: Literature review and practical guideline

Thyroid hormones play an essential role in central nervous system development, normal physiological brain function, and repair mechanisms. On one hand, thyroid hormone alterations influence cortical excitability, and on the other hand antiseizure medications (ASMs) are associated with alterations in thyroid hormone metabolism. Although this interaction has long been described, and epilepsy is a common and chronic neurological disease, studies describing the interplay are often small and retrospective. We performed a systematic review of the current literature on epilepsy, ASMs, and thyroid hormone metabolism. Forty-seven studies were included. Most studies were retrospective cross-sectional studies (n = 25) and investigated thyroid function alterations in patients on older ASMs such as phenobarbital, phenytoin, carbamazepine, and valproate. Overall, almost one third of patients with epilepsy had thyroid hormone alterations, especially patients on valproate (25%) and carbamazepine (10%-25%). Studies with patients receiving polytherapy are scarce, but reported a higher risk for hypothyroidism in patients with older age (p = .004), female sex (p = .014), longer duration of epilepsy (p = .001), intractable epilepsy (p = .009), and polytherapy. Studies on newer ASMs are also limited, and further studies on an interplay with thyroid hormone homeostasis are essential to improve the care for epilepsy patients. ASMs are associated with alterations in thyroid hormone metabolism. Thyroid function monitoring is indicated in patients on ASMs, especially those with refractory epilepsy and those on polytherapy. We provide a practical guideline for thyroid function monitoring for the clinician taking care of patients on ASMs.

Carbamazepine drug effect simulating biochemical central hypothyroidism in a patient with Bardet-Biedl syndrome

Carbamazepine (CBZ) is a medication used commonly in epilepsy. Decreases in free T4 levels simulating central hypothyroidism have been reported, although the clinical significance is still unclear. We present a 24-year-old man with Bardet-Biedl syndrome (BBS) who was found to have isolated biochemical central hypothyroidism. BBS is a ciliopathy occasionally associated with anterior pituitary dysfunction. While taking CBZ for epilepsy, his TSH was 1.73 mIU/L (reference range: 0.20-4.00 mIU/L) with a low free T4 of 6.6 pmol/L (reference range: 10.0-26.0 pmol/L). Pituitary MRI was normal. Although treated with levothyroxine initially, his apparent biochemical central hypothyroidism was later recognised as secondary to CBZ drug effect. This was confirmed with a normal free T4 of 12.2 pmol/L while he was off CBZ and levothyroxine. Despite the association between CBZ and biochemical central hypothyroidism, nearly all patients remain clinically euthyroid. This effect is reversible and recognition could lead to reductions in unnecessary thyroid replacement therapy if CBZ is discontinued.

Low free thyroxine and normal thyroid-stimulating hormone in infants and children: possible causes and diagnostic work-up

Screening for hypo- or hyperthyroidism in adults is generally done by measuring the serum thyrotropin (thyroid-stimulating hormone, TSH) concentration. This is an efficient approach in case of suspected acquired thyroid disease. However, in infants and children, congenital hypothalamus-pituitary-thyroid (HPT) axis disorders also need to be considered, including primary and central congenital hypothyroidism, and even rarer thyroid hormone receptor and transporter defects. In primary congenital hypothyroidism, TSH will be elevated, but in the other congenital HPT axis disorders, TSH is usually within the normal range. Free thyroxine (FT4) assessment is essential for the diagnosis in these conditions.Conclusion: Here we discuss a number of rare congenital HPT axis disorders in which TSH is normal, but FT4 is low, and provide a clinical algorithm to distinguish between these disorders. What is Known: • A single thyroid-stimulating hormone (TSH) measurement is an appropriate screening method for primary hypothyroidism. • For central hypothyroidism and rare thyroid hormone receptor and transporter defects a free thyroxine (FT4) measurement is essential for the diagnosis because TSH is usually normal. What is New: • Here we present a new problem-oriented clinical algorithm including a diagnostic flow-chart for low FT4 and normal TSH in infants and children.

The effect of levetiracetam and oxcarbazepine monotherapy on thyroid hormones and bone metabolism in children with epilepsy: A prospective study

BACKGROUND

Long-term treatment with certain antiepileptic drugs may lead to thyroid function disturbances or alterations in bone metabolism; the data on the effects of new antiepileptic drugs on this are limited and conflicting, especially in children with epilepsy. Therefore, the aim of this study was to investigate the effects of levetiracetam and oxcarbazepine on thyroid hormone levels and bone metabolism in children with epilepsy.

METHODS

A total of 51 children with new-onset partial epilepsy were selected. They were randomly treated with either levetiracetam (n = 25), or oxcarbazepine (n = 26) monotherapy. Eight of the 51 patients were excluded for failing to take the drug continuously or failing to undergo a regular review. Thus, 43 patients were finally included (levetiracetam: 23 patients, oxcarbazepine: 20 patients). A control group consisting of age- and sex-matched healthy subjects (n = 20) was included for comparison. Serum triiodothyronine, tetraiodothyronine, free triiodothyronine, free thyroxine, thyroid-stimulating hormone, calcium, phosphorus, alkaline phosphatase, osteocalcin, parathyroid hormone, and 25-hydroxyvitamin D levels and bone mineral density values were measured before and at 6 and 12 months after therapy in all groups.

RESULTS

At baseline, thyroid hormone levels, bone metabolism index, and bone mineral density values did not differ between the control group and the drug-treated groups. Levetiracetam-treated patients showed no significant changes in thyroid hormone levels, bone metabolism, and bone mineral density during the 12-month follow-up period compared with baseline values. In the oxcarbazepine group, compared to baseline values, serum free thyroxine levels decreased after 12 months of treatment (Z = -3.115, p = 0.002), and after 6 and 12 months of treatment, calcium levels decreased (Z = -3.705, p < 0.001 and Z = -3.884, p < 0.001, respectively) and parathyroid hormone levels increased (Z = -3.698, p < 0.001 and Z = -3.921, p < 0.001, respectively); however, all other parameters did not differ from baseline values.

CONCLUSION

Our data show that levetiracetam treatment has no significant effect on thyroid function and bone metabolism in children with epilepsy. Long-term use of oxcarbazepine may reduce serum free thyroxine levels, resulting in impaired thyroid function, and may reduce serum calcium and increase parathyroid hormone levels, leading to bone metabolism disorders.

Thyroid Functions in Children on Levetiracetam or Valproic Acid Therapy

The aim of this study was to investigate the thyroid functions in children receiving levetiracetam or valproate monotherapy. We retrospectively reviewed the records of children with controlled epilepsy receiving valproic acid (VPA group) or levetiracetam monotherapy (LEV group) for at least 6 months. Free thyroxine 4 levels (fT4) and thyroid stimulating hormone (TSH) levels were compared between VPA group, LEV group, and age- and gender-matched healthy children (control group). A total of 190 children were included in the study: 63 were in the VPA, 60 in the LEV, and 67 in the control group. Although there was no significant difference regarding average fT4 levels, higher TSH levels were found in the VPA group when compared with the LEV and control groups (p < 0.001 and p < 0.001, respectively). There was no significant difference in terms of fT4 and TSH values in the LEV group when compared with the control group (p = 0.56 and p = 0.61, respectively). Subclinical hypothyroidism (defined as a TSH level above 5 uIU/mL with a normal fT4 level was detected in 16% of patients in the VPA group, none in the LEV and control groups. Our study found that VPA therapy is associated with an increased risk of subclinical hypothyroidism while LEV had no effect on thyroid function tests.

Effects of perampanel add-on therapy on immunoglobulin levels in pediatric patients with epilepsy

BACKGROUND

Perampanel (PER) has a unique pharmacological mechanism and marked efficacy in both focal and generalized epilepsy, but may cause adverse events similar to those of other antiepileptic drugs (AEDs). AEDs can affect multiple organ systems, as well as thyroid function, lipid profiles, and immunoglobulin levels; the low free T4 levels, hyperlipidemia, and low immunoglobulin levels can be caused by AEDs. While many studies have examined conventional AEDs, little is known about the long-term effects of PER on blood parameters.

METHODS

We retrospectively reviewed the medical records of 18 pediatric patients with epilepsy who were treated with PER added to >1 other AED. Blood parameters (e.g., blood cell counts, biochemical and thyroid function, and immunoglobulin levels) were investigated at baseline and at 6 and 12 months after initiation of PER.

RESULTS

PER did not affect the blood counts, transaminase levels, lipid profile, or thyroid function at 12 months after initiation of PER. However, IgA levels significantly increased (p = 0.00319) without symptoms. IgM levels increased temporarily, but had returned to baseline by 12 months after initiation of PER.

CONCLUSIONS

IgA levels were elevated at 12 months after initiation of PER in pediatric patients with intractable epilepsy, although no symptoms were observed. PER did not affect other parameters, including lipid profile and thyroid function.

Epilepsy and autoimmune diseases: Comorbidity in a national patient cohort

PURPOSE

To examine if autoimmune disorders occur with an increased frequency in patients with epilepsy. An autoimmune etiology of epilepsies has been suggested. By using data from The Norwegian Prescription Database (NorPD) we have surveyed a national cohort of patients with active epilepsy treated with antiepileptic drugs.

METHODS

NorPD contains all prescriptions of drugs dispensed at pharmacies in Norway since 2004. We received data of all drugs prescribed January 2004 - June 2014 for patients receiving an antiepileptic drug.79 751 patients receiving at least two prescriptions of antiepileptic drugs with the reimbursement code for epilepsy were included. To examine autoimmune comorbidity, medications specific for autoimmune diseases were retrieved. Standardized Incidence Ratios (SIR) with 95 % confidence interval (CI) were used to determine whether the occurrence of the prescribed autoimmune drugs in the epilepsy group deviated from the general population. Subgroups stratified for sex and age were examined.

RESULTS

The epilepsy patients were more often treated with insulin and insulin analogs, SIR 1.8 (95 % CI 1.7-1.9); thyroid substitution, SIR 1.7 (95 % CI 1.7-1.8); pyridostigmine, SIR 1.5 (95 % CI 1.1-2.1); multiple sclerosis (MS) medications, SIR 4.9 (95 % CI 4.6-5.3); and immunosuppressive drugs SIR 1.2 (95 % CI 1.1-1.2). All epilepsy subgroups were more often than expected treated with thyroid substitution.

CONCLUSIONS

Based on a large, unselected patient cohort we find that epilepsy patients more often are prescribed medications used to treat type 1 diabetes mellitus, hypothyroidism, myasthenia gravis and MS. This was true for both men and women, and in most age-groups.

Lipid and thyroid hormone levels in children with epilepsy treated with levetiracetam or carbamazepine: A prospective observational study

Although previous studies have investigated the influence of antiepileptic drugs (AEDs) on lipid profiles and thyroid hormone levels, there is little evidence regarding the effects of levetiracetam (LEV). Therefore, we conducted a prospective longitudinal study to evaluate the effects of LEV and carbamazepine (CBZ) treatment on lipid profile and thyroid hormone levels in patients newly diagnosed with epilepsy. Inclusion criteria were as follows: (a) age between 4 and 15 years, (b) diagnosis of epilepsy with at least two focal seizures within a year, and (c) newly treated with LEV or CBZ monotherapy. Serum lipid profile and thyroid hormone levels were measured before and after 1 and 6 months of AED initiation. Among the 21 included patients (LEV: 13 patients, CBZ: 8 patients), all but one patient in the LEV group continued AED monotherapy during the study period. Although triglyceride (TG) levels tended to be increased in the CBZ group (baseline: 58.3 ± 22.0 mg/dl, 1 month: 63.8 ± 21.6 mg/dl, 6 months: 92.3 ± 63.6 mg/dl, p = 0.22, analyses of variance (ANOVA)), there were no significant changes in total cholesterol (TC), TG levels, high-density lipoprotein cholesterol (HDL-C), or low-density lipoprotein cholesterol (LDL-C) in either group. Serum free thyroxine (fT4) levels were significantly decreased in the CBZ group (baseline: 1.15 ± 0.06 ng/dl, 1 month: 1.00 ± 0.16 ng/dl, 6 months: 0.98 ± 0.14 ng/dl, p = 0.03, ANOVA). In contrast, there were no significant changes in fT4 or thyroid-stimulating hormone (TSH) levels in the LEV group. The results of the present study suggest that LEV monotherapy does not affect lipid profile or thyroid function while CBZ monotherapy may cause thyroid dysfunction.

Levetiracetam for epilepsy: an evidence map of efficacy, safety and economic profiles

OBJECTIVE

To evaluate the efficacy, safety and economics of levetiracetam (LEV) for epilepsy.

MATERIALS AND METHODS

PubMed, Scopus, the Cochrane Library, OpenGrey.eu and ClinicalTrials.gov were searched for systematic reviews (SRs), meta-analyses, randomized controlled trials (RCTs), observational studies, case reports and economic studies published from January 2007 to April 2018. We used a bubble plot to graphically display information of included studies and conducted meta-analyses to quantitatively synthesize the evidence.

RESULTS

A total of 14,803 records were obtained. We included 30 SRs/meta-analyses, 34 RCTs, 18 observational studies, 58 case reports and 2 economic studies after the screening process. The included SRs enrolled patients with pediatric epilepsy, epilepsy in pregnancy, focal epilepsy, generalized epilepsy and refractory focal epilepsy. Meta-analysis of the included RCTs indicated that LEV was as effective as carbamazepine (CBZ; treatment for 6 months: 58.9% vs 64.8%, OR=0.76, 95% CI: 0.50-1.16; 12 months: 54.9% vs 55.5%, OR=1.24, 95% CI: 0.79-1.93), oxcarbazepine (57.7% vs 59.8%, OR=1.34, 95% CI: 0.34-5.23), phenobarbital (50.0% vs 50.9%, OR=1.20, 95% CI: 0.51-2.82) and lamotrigine (LTG; 61.5% vs 57.7%, OR=1.22, 95% CI: 0.90-1.66). SRs and observational studies indicated a low malformation rate and intrauterine death rate for pregnant women, as well as low risk of cognitive side effects. But psychiatric and behavioral side effects could not be ruled out. LEV decreased discontinuation due to adverse events compared with CBZ (OR=0.52, 95% CI: 0.41-0.65), while no difference was found when LEV was compared with placebo and LTG. Two cost-effectiveness evaluations for refractory epilepsy with decision-tree model showed US$ 76.18 per seizure-free day gained in Canada and US$ 44 per seizure-free day gained in Korea.

CONCLUSION

LEV is as effective as CBZ, oxcarbazepine, phenobarbital and LTG and has an advantage for pregnant women and in cognitive functions. Limited evidence supports its cost-effectiveness.

REGISTERED NUMBER

PROSPERO (No CRD 42017069367).