Increased frequency of goitre in epileptic patients on long-term phenytoin or carbamazepine treatment

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.

The problem of osteoporosis in epileptic patients taking antiepileptic drugs

INTRODUCTION

Epilepsy is a common neurological disorder associated with recurrent seizures. Therapy with antiepileptic drugs (AEDs) helps achieve seizure remission in approximately 70% of epileptic patients. Treatment with AEDs is frequently lifelong and there are reports suggesting its negative influence on bone health. This is especially important in terms of general occurrence of osteoporosis, affecting over 50 million people worldwide.

AREAS COVERED

This study refers to two main groups of AEDs: hepatic enzyme inducers (carbamazepine, oxcarbazepine, phenobarbital, phenytoin, primidone and topiramate) and non-inducers (clobazam, clonazepam, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, pregabalin, tiagabine, valproate, vigabatrin and zonisamide). Some reports indicate that enzyme inducers may exert a more negative influence on bone mineral density (BMD) compared to non-inducers. Bone problems may appear in both sexes during AED therapy, although women are additionally burdened with postmenopausal osteoporosis. Supplementation of vitamin D and calcium in patients on AEDs is recommended.

EXPERT OPINION

Apart from enzyme inducers, valproate (an even enzyme inhibitor) may also negatively affect BMD. However, the untoward effects of AEDs may depend upon their doses and duration of treatment. Although the problem of supplementation of vitamin D and calcium in epileptic patients on AEDs is controversial, there are recommendations to do so.

Assessment of low-density lipoprotein oxidation, paraoxonase activity, and arterial distensibility in epileptic children who were treated with anti-epileptic drugs

OBJECTIVE

Studies show that anti-epileptic drugs increase oxidative stress. Thus, low-density lipoprotein oxidation increases and atherogenesis is induced. Paraoxonase-associated high-density lipoprotein protects low-density lipoprotein and high-density lipoprotein oxidation. The effects of anti-epileptic drugs on paraoxonase activity has not been investigated yet. The aim of this study is to investigate the effect of anti-epileptic drugs on paraoxonase activity, lipid profiles, folat, vitamin B12, homocysteine, thyroid hormones, apolipoprotein A-1, total anti-oxidant capacity, malondialdehyd, nitric oxide, and oxidised low-density lipoprotein. The association with carotid-femoral pulse wave velocity and current biochemical parameters had been searched for assessing the effects of anti-epileptic drugs on the vascular system.

PATIENTS AND METHODS

We recruited 59 epileptic patients treated with anti-epileptic drugs and 23 controls (group IV) at least 6 months ago. The epileptic group was divided into three groups by receiving anti-epileptic drugs as follows: group I: carbamazepine, group II: valproic acid, and group III: carbamazepine and valproic acid. Arterial distensibility was assessed with the Complior device.

RESULTS

There was no difference between the current biochemical parameters in epileptic children. Serum-free T4 was decreased, when compared with group IV. Thyroid-stimulating hormone was increased in group II, compared with group IV. The carotid-femoral pulse wave velocity was increased in group III, compared with group IV. The carotid-femoral pulse wave velocity was correlated with thyroid-stimulating hormone and valproic acid levels.

CONCLUSIONS

Anti-epileptic drugs may induce atherogenesis by affecting the thyroid hormones. According to the current data, the effects of thyroid hormones on vascular system may be independent of other biochemical markers. Epileptic patients using anti-epileptic drugs must be followed closely for arterial stiffness, and also for the development and progression of atherosclerosis.

Phenobarbital Confers its Diverse Effects by Activating the Orphan Nuclear Receptor Car

In the early 1960s, phenobarbital (PB) was shown to induce hepatic drug metabolism and the induction was implicated in the molecular mechanism of drug tolerance development. Since then, it has become evident that PB not only induces drug metabolism, but also triggers pleiotropic effects on liver function, such as cell growth and communication, proliferation of the endoplasmic reticulum, tumor promotion, glucose metabolism, steroid/thyroid hormone metabolism, and bile acid synthesis. Upon activation by PB and numerous PB-type inducers, the nuclear receptor CAR mediates those pleiotropic actions by regulating various hepatic genes, utilizing multiple regulatory mechanisms.

Thyroid function and volume in epileptic children using carbamazepine, oxcarbazepine and valproate

BACKGROUND

The aim of the present study was to investigate the effects of carbamazepine (CBZ), oxcarbazepine (OXC), and valproic acid (VPA) on thyroid function and volume in epileptic children.

METHODS

Fifty-three epileptic children (age, 3-17 years) treated with OXC (n = 10), CBZ (n = 12), or VPA (n = 31) at least for 1 year were evaluated in terms of thyroid hormones, thyroid-stimulating hormone (TSH) levels, response to thyrotropin-releasing hormone (TRH) stimulation test, and thyroid volumes.

RESULTS

The patients in the OXC and CBZ groups had similar total thyroxin (TT4) and free T4 (fT4) median levels that were significantly lower than those of the VPA group (P < 0.016). Total tri-iodothyrosin median levels were lower in the CBZ group compared to the VPA group (P < 0.016). Basal TSH levels and thyroid volumes were similar in all groups (P > 0.016). One child from the OXC group (10%), one from the CBZ group (%8.3), and six from the VPA group (19.3%) had hypothyroidic status according to the TRH stimulation test. No statistically significant correlations were found between thyroid gland volume and thyroid function variables and between anti-epileptic drug receiving time and thyroid function or thyroid volume, respectively, in any of the groups (P > 0.05).

CONCLUSIONS

Thyroid function should be evaluated periodically in children using CBZ, OXC or VPA. The children taking VPA seems to be at greater risk compared to children onr CBZ or OXC therapy. Except for the basal TSH values in the VPA group, the parameters predictive for the subclinical hypothyroid status remain to be evaluated in further studies.

Evolution of subclinical hypothyroidism in children treated with antiepileptic drugs

The concentration levels of serum free thyroxine, serum free triiodothyronine, and thyroid-stimulating hormone were measured in 20 children receiving carbamazepine, 32 children receiving valproic acid, and 5 children receiving phenobarbital at the following times: (1) during chronic treatment, and (2) 3 months after the end of treatment with antiepileptic drugs. Patients during chronic treatment revealed significant changes in serum thyroid hormones, especially the children treated with carbamazepine and valproic acid. A number of children receiving long-term therapy with the two last antiepileptic drugs had varying grades of subclinical hypothyroidism. Three months after the end of treatment, a complete return to normal of all parameters was observed. These data demonstrate that the changes induced by these drugs are transient and reversible.

Carbamazepine and risk of hypothyroidism: a prospective study

OBJECTIVES - While carbamazepine (CBZ) decreases thyroid hormone concentrations it rarely causes hypothyroidism. We assessed prospectively the early effect of CBZ on thyroid status in thyroxine-supplemented hypothyroid patients, when compared with patients without a thyroid disorder. METHODS - In 29 patients, thyrotropin (TSH), total thyroxine (TT4) and free thyroxine (FT4) serum levels were assayed before starting CBZ, and then weekly for 7 weeks. Nineteen patients with no thyroid disorder (group A) were compared with 10 thyroxine-supplemented hypothyroid patients, stable before CBZ treatment (group B). RESULTS - In group A, TT4 decreased significantly by ca. 15-25%, starting from the first week (Friedman, P < 0.001). FT4 decline was smaller (ca. 10-15%) and delayed till the second week. FT4/TT4 ratio increased significantly (P < 0.001), while TSH only slightly (P = 0.073), never exceeding normal range. In group B, similar TT4 and FT4 decline was followed by significantly increasing TSH (P = 0.011), while the FT4/TT4 ratio was not significantly changed. In 3 of 10 patients TSH rose over 5 mIU/l, necessitating treatment adjustment. CONCLUSIONS - In patients with no thyroid disorder, CBZ causes hormonal changes of no clinical relevance, due to adaptive response. In T4-supplemented hypothyroid patients this adaptation is lacking, CBZ may precipitate subclinical or overt hypothyroidism, and early thyroid function monitoring seems advisable.

Thyroid dysfunction associated with increased low-density lipoprotein cholesterol in epileptic children treated with carbamazepine monotherapy: a causal relationship?

OBJECTIVE

Lipid abnormalities and thyroid dysfunction have been reported in patients treated with antiepileptic drugs. The aim of this study was to evaluate prospectively the association between thyroid and lipid profile in children treated with carbamazepine (CBZ) monotherapy.

MATERIALS AND METHODS

Thyroid function was evaluated in 18 epileptic children, previously reported with CBZ-induced changes in serum lipid profile, before and at 6, 12 and 24 months of CBZ monotherapy.

RESULTS

All children had normal thyroid function before the initiation of CBZ treatment. During CBZ therapy thyroid dysfunction, with increased thyrotropin (TSH) and decreased thyroxine (T4), free thyroxine (FT4) and triiodothyronine (T3) was found, while, significant association was revealed between serum low-density lipoprotein cholesterol (LDL-C) and TSH levels at 6 (r=0.469; p=0.043) and 12 (r=0.730; p=0.001) months of treatment.

CONCLUSION

Lipid abnormalities may be associated with thyroid hormone disturbance in children treated with CBZ monotherapy. Since thyroid dysfunction and hypercholesterolemia are both associated with a higher atherosclerotic risk special attention and further studies are needed in epileptic patients treated with CBZ monotherapy.

The Evaluation of Thyroid Functions, Thyroid Antibodies, and Thyroid Volumes in Children with Epilepsy during Short-Term Administration of Oxcarbazepine and Valproate

PURPOSE

The aim of this study was to evaluate the effects of short-term oxcarbazepine (OXC) and valproate (VPA) monotherapy on thyroid functions in children.

METHODS

Fifty-five newly diagnosed epileptic children with normal thyroid functions (confirmed with the thyrotropin releasing hormone stimulation test) participated in this study. VPA treatment was started in 30 patients and OXC in 25 patients. Serum thyroxine (T(4)), free thyroxine (fT(4)), triiodothyronine (T(3)), free triiodothyronine (fT(3)), reverse T3 (rT(3)), thyroid peroxidase antibodies (TPO-ab), and urine iodine levels were evaluated at baseline and at the third and sixth months of therapy.

RESULTS

In the OXC group, serum T(4), fT(4), T(3), fT(3), and rT(3) levels were found to be decreased at the third and sixth months, the differences were significant compared to the baseline values except for fT(3) levels at the third month and fT(4) and rT(3) levels at the sixth month (p < 0.05). At the sixth month, serum T(4) level dropped below the normal reference value in 8 (32%), fT(4) in 5 (20%), T(3) in 4 (16%), and fT(3) in 3 (12%) patients. In the VPA group, mean T(4), fT(4), T(3), fT(3), and rT(3) levels at 3 and 6 months remained similar compared to the baseline values (p > 0.05). Mean serum thyroid stimulating hormone levels increased significantly at the sixth month compared to the baseline values in the VPA group (p < 0.05) while it remained unchanged in the OXC group (p > 0.05). There was no effect of either drug on urinary iodine excretion and serum TPO-ab levels remained in normal ranges throughout the study.

CONCLUSIONS

In this prospective study, it is documented that children under short-term OXC or VPA therapy showed altered thyroid functions similar to the changes observed after long-term treatment. Although, the clinical significance of these results need to be evaluated with future studies, this observation of altered thyroid functions points out that thyroid functions may need to be monitored closely in children receiving antiepileptic treatment, even in the short-time interval.

Alteration of thyroid hormone homeostasis by antiepileptic drugs in humans: involvement of glucuronosyltransferase induction

RATIONALE

The aim of this review article is to analyse which antiepileptic drugs (AEDs) alter thyroid hormone homeostasis in humans and when this can be explained, at least partially, by the induction of the glucuronoconjugation pathways.

METHODS

Electronic databases were searched which have provided more than 300 articles. These have been integrated with fundamental books and personal information by experts in the different areas examined.

RESULTS

Alteration of thyroid hormone homeostasis by phenobarbital/primidone, phenytoin, and carbamazepine clearly occurs in humans. However, it is not associated with thyroid-stimulating hormone (TSH) increase and the clinical significance of altered serum concentrations of thyroid hormones by these antiepileptic drugs has remained unclear. The published information on the effect of the other antiepileptic drugs examined in this review article on thyroid hormones is lacking (felbamate, pregabalin, zonisamide) or limited. Oxcarbazepine appears to have some effects. Topiramate would need further investigations as well as gabapentin. Levetiracetam, tiagabine, vigabatrine, and lamotrigine do not alter at all, or only minimally, thyroid hormone homeostasis.

CONCLUSION

Concerning the antiepileptic drugs which alter thyroid hormone homeostasis, it is highly probable that the mechanism of induction of uridine diphosphate glucuronosyltransferases (UGT) is involved, at least partially, in such an alteration. However, it is not possible to estimate the relative contribution of the UGT induction by these drugs on the total alteration observed in thyroid hormone levels, as other mechanisms not investigated, or not examined in the present article, could contribute.

Serum thyroid hormone balance and lipid profile in patients with epilepsy

PURPOSE

Patients with epilepsy may exhibit changes in thyroid hormone balance, lipids and lipoproteins concentrations. The suggestion that lipid abnormalities are associated with subclinical thyroid dysfunction remains controversial. The aim of this study was to analyze whether thyroid dysfunction encountered in patients with epilepsy would also be associated with abnormal lipid profile.

METHODS

Eighty-eight patients with epilepsy and 30 control subjects were included in the study. A fasting blood sample for thyroid hormones, lipid profile and GGT determination was obtained.

RESULTS

The serum levels of FT3 was elevated in 10.2% of patients, FT4 was low in 28.4%, TSH was high in 4.6% and low in 2.3%. 13.6% of patients had high TC, 17.1% had high LDL-c, 60.2% had marked reduction of HDL-c levels (P<0.0001) and only 2.3% had high TG levels. Abnormalities were predominated in CBZ-treated patients. 27.3% patients with abnormal hormones had abnormal lipid profile. Significant association was identified between the serum TC, LDL-c, TG, GGT and EIAEDs and between the duration of illness and TG (r=-0.411; P=0.017), and FT4 (r=-0.412; P=0.018). HDL was higher in women than men (r=0.416; P<0.002). However, changes in HDL-c levels associated neither with duration of illness, type or serum levels of AEDs nor with age or degree of control on AEDs.

CONCLUSIONS

Our results support that (1) altered lipid metabolism might be associated but not solely influenced by thyroid hormones and (2) enzyme induction is not the main or only reason for altered thyroid function or HDL-c among patients with epilepsy. Hypothalamic/pituitary dysregulation by precisely mechanism caused by epilepsy itself or AEDs seems possible and (3) it is important to recognize that patients with epilepsy are at great risk for atherosclerosis, hence monitoring and correction of the culprit risks are mandatory.

Role of the constitutive androstane receptor in xenobiotic-induced thyroid hormone metabolism

The induction of hepatic drug metabolizing enzymes alters not only the metabolism of the xenobiotic substances that induce them but also the metabolism of various endogenous hormones. The xenobiotic receptor constitutive androstane receptor (CAR) (NR1I3) mediates the well-studied induction of CYP2B genes and other drug-metabolizing enzymes by phenobarbital (PB), an antiepileptic drug that has been shown to alter thyroid hormone (TH) levels. Here we show that CAR is required for PB-mediated disruption of TH homeostasis and the induction of thyroid follicular cell proliferation. Treatment with PB or the more potent and more effective CAR ligand 1, 4-bis-[2-(3, 5,-dichloropyridyloxy)] benzene resulted in universal induction of thyroid hormone glucuronidation and sulfation pathways in a CAR-dependent manner. This resulted in a decrease in serum T4 concentration and a concomitant increase in serum TSH levels. CAR activation also decreased serum T3 levels in mice in which T3 production was blocked. The increase in serum TSH levels resulted in the stimulation of thyroid-follicular cell proliferation. These results highlight the central role of the xenosensor CAR in drug-hormone interactions.

Thyroid function in men taking carbamazepine, oxcarbazepine, or valproate for epilepsy

PURPOSE

Antiepileptic drugs (AEDs) may affect serum thyroid hormone concentrations. This study aimed to evaluate thyroid function in men taking carbamazepine (CBZ), oxcarbazepine (OCBZ), or valproate (VPA) for epilepsy.

METHODS

Ninety men with epilepsy (40 taking CBZ, 29 taking OCBZ, and 21 taking VPA monotherapy) and 25 control subjects participated in the study. After clinical examination, a blood sample for hormone, gamma-glutamyl-transferase (GGT) and antibody (ab) assays was obtained.

RESULTS

Serum thyroxine (T4) and free thyroxine (FT4) concentrations were low in men taking CBZ or OCBZ. Forty-five percent of men taking CBZ and 24% of men taking OCBZ had serum T4 and/or FT4 levels below the reference range. However, no correlations were found between T4 or FT4 and GGT concentrations in men taking CBZ or OCBZ. Thirteen percent of men taking CBZ, 17% of men taking OCBZ, and 6% of control men had increased levels of thyroid peroxidase (TPO)-ab and/or thyroglobulin (TG)-ab, but these were not associated with altered serum thyroid hormone concentrations. Serum triiodothyronine and thyrotropin levels in men taking CBZ or OCBZ were normal. In men taking VPA, the concentrations of thyroid hormones, thyrotropin, and antithyroid ab were normal.

CONCLUSIONS

Serum thyroid hormone concentrations are low in CBZ- or OCBZ-treated men. However, these low levels do not seem to be due to liver enzyme induction or activation of immunologic mechanisms. Therefore, interference with hypothalamic regulation of thyroid function by CBZ and OCBZ seems possible. VPA does not have any significant effects on thyroid function.

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.

Effects Of Carbamazepine On The Hypothalamic-Pituitary-Thyroid Axis

OBJECTIVE

To evaluate the effects of treatment with carbamazepine on the hypothalamic-pituitary-thyroid axis and thyroid hormone concentrations in patients with epilepsy.

METHODS

We undertook a prospective study in seven subjects in whom the diagnosis of epilepsy had been established and a regimen of carbamazepine (200 mg three times a day) was initiated. All participants underwent 24-hour 123 I thyroid uptake studies, as well as assessment of the basal thyrotropin concentration and the thyrotropin response to intravenous administration of thyrotropin-releasing hormone. In addition, thyroxine (T(4)), free T(4) index, triiodothyronine (T(3)), free T(3) index, reverse T(3), and T(3) resin uptake were determined before initiation of carbamazepine treatment and again after 3 to 4 months of carbamazepine therapy.

RESULTS

Serum T(4), T(3), and free T(4) index decreased significantly (P<0.05) after therapy with carbamazepine, whereas no significant alterations were noted in T(3) resin uptake, free T(3) index, and reverse T(3) concentrations. A significant increase occurred in basal serum thyrotropin level (P<0.05). Moreover, the peak thyrotropin concentration, the absolute change from the basal thyrotropin level, and an integrated thyrotropin response expressed as cumulative response to thyrotropin-releasing hormone stimulation were all significantly increased after carbamazepine therapy in comparison with values documented before initiation of therapy (P<0.05 for all comparisons). Finally, 24-hour 123 I uptake by the thyroid gland increased slightly after carbamazepine therapy, but the change was not statistically significant. All values determined both before and after carbamazepine therapy remained within normal ranges.

CONCLUSION

Carbamazepine therapy induces significant alterations in serum thyroid hormone concentrations as well as in the hypothalamic-pituitary-thyroid axis. Nevertheless, patients receiving carbamazepine treatment continue to remain euthyroid despite these significant changes.

Effects of thyroid status and thyrostatic drugs on hepatic glucuronidation of lodothyronines and other substrates in rats : Induction of phenol UDP-glucuronyltransferase by methimazole

Glucuronidation of iodothyronines in rat liver is catalyzed by at least three UDP-glucuronyltransferases (UGTs): bilirubin UGT, phenol UGT, and androsterone UGT. Bilirubin and phenol UGT activities are regulated by thyroid hormone, but the effect of thyroid status on hepatic glucuronidation of iodothyronines is unknown. We examined the effects of hypothyroidism induced by treatment of rats with propylthiouracil (PTU) or methimazole (MMI) or by thyroidectomy as well as the effects of T4-induced hyperthyroidism on the hepatic UGT activities for T4, T3, bilirubin,p-nitrophenol (PNP), and androsterone. Bilirubin UGT activity was increased in MMI- or PTU-induced hypothyroid and thyroidectomized rats, and decreased in hyperthyroid animals. T4 and, to a lesser extent, T3 UGT activities were increased in MMI- or PTU-induced hypothyroid rats, and T4 but not T3 glucuronidation also showed a significant increase in thyroidectomized rats. T4 but not T3 UGT activity was slightly decreased in hyperthyroid rats. While PNP UGT activity was decreased in thyroidectomized rats and increased in hyperthyroid animals, it was also markedly increased by MMI and slightly increased by PTU-induced hypothyroidism. In T4-substituted rats, MMI did not affect T4, T3, bilirubin and androsterone UGT activities but again strongly induced PNP UGT activity, indicating that this represented a direct induction of PNP UGT by the drug independent of its thyrostatic action. Androsterone UGT activity was hardly affected by thyroid status. Our results suggest a modest, negative control of the hepatic glucuronidation of thyroid hormone by thyroid status, which may be mediated by changes in bilirubin UGT activity. To our knowledge, this is the first report of the marked induction of a hepatic enzyme by MMI, which is not mediated by its thyroid hormone-lowering effect.

The effects of carbamazepine on resting metabolic rate and thyroid function in depressed patients

Resting metabolic rate and thyroid hormone levels were studied in 11 patients with affective disorders before and during treatment with carbamazepine (CBZ). CBZ has been previously reported to reduce thyroid hormones, but the metabolic consequence of this effect has not been explored. During CBZ treatment, thyroid hormones decreased significantly (T4, 7.53 versus 5.74 micrograms/dl, p less than 0.001), whereas the resting metabolic rate (RMR) did not (31.6 versus 30.7 kcal/m2/hr). Baseline RMRs were low and the expected positive relationship between RMR and weight was disrupted in females. The extent of previous exposure to tricyclic and monoamine oxidase inhibitors antidepressant treatment was significantly associated with lower baseline RMRs. We conclude that CBZ has no significant effect on RMR despite robust decreases in thyroid function.

Thyroid abnormalities during lithium treatment

Thyroid function was evaluated in 150 Sardinian outpatients at different stages of lithium treatment. A visible and/or palpable goitre was found in 51% of patients, and there was no apparent correlation with the duration of treatment. No cases of symptomatic hypothyroidism were observed, but subclinical hypothyroidism was present in 19% of patients. The prevalence of specific antithyroid antibodies was positively correlated with age and duration of lithium treatment, and was higher in women. Subclinical hypothyroidism was observed in 53% of antibody-positive lithium-treated patients. Carbamazepine in combination with lithium was associated with significantly lower levels of total T4 and T3 than with lithium alone, and the ratios between total and free hormones were also decreased.

Review: thyroid function in psychiatric illness

The development of highly sensitive immunometric assays for thyroid-stimulating hormone (TSH) has provided increased understanding of thyroid hormone regulation but, paradoxically, has contributed to a kaleidoscopic complexity of thyroid function test variability in hospitalized patients with nonthyroidal illness (NTI). In primary hypothyroidism, an elevated TSH is the most sensitive chemical index available, although early cases may show a hyperresponse of TSH to thyrotropin-releasing hormone (TRH) stimulation when the TSH is still within the normal range. The ability of the new TSH assays to discriminate between normal and low levels now allows the diagnosis of thyrotoxicosis to be confirmed by a suppressed TSH in the presence of elevated serum thyroxine (T4) and/or triiodothyronine (T3). The TRH stimulation test is virtually obsolete for the diagnosis of thyrotoxicosis but remains of much interest in the investigation of psychiatric syndromes. Approximately 25% of patients with depression have a blunted TSH response (a rise of less than 5 microU/mL) that differs from thyrotoxicosis, wherein the TSH response is suppressed under 1 microU/mL. The cause of the blunted TSH is uncertain but is not due to hyperthyroidism. In contrast, close to 15% may have a TSH hyperresponse to TRH and/or elevated antithyroid antibodies. Thyroid hormone treatment may benefit the depression in some of these cases. In the sick thyroid state of nonthyroidal illness, a low T3 level is the initial manifestation. In more severe cases, the T4 also falls, the free T4 level in this situation is variable, both normal and low levels being reported from different laboratories. A diagnosis of hypothyroidism requiring treatment with thyroid hormone therapy is unlikely unless there is a concomitant lowfree T4 and elevated TSH in a patient who is not in the process of recovery. In acute psychiatric admissions, there is a high frequency of hyperthyroxinemia. The TSH in these cases is generally either normal or high, suggesting central activation of the hypothalamic-pituitary-thyroid axis. In most instances, the thyroid function tests normalize within 2 weeks, and treatment directed toward the thyroid gland is not indicated. Suppressed TSH levels, usually associated with a normal free T4, has also been described in such patients. Finally, various medications utilized in psychiatric practice have diverse effects on thyroid function and can cause diagnostic difficulty. These include lithium, phenytoin sodium, and carbamazepine, and their effects are reviewed.

Supplementary thyroxine therapy in patients with hypothyroidism induced by long-term anticonvulsant therapy

Of 287 patients under long-term therapy with anticonvulsants, 24 with low serum thyroxine and free thyroxine concentrations were prescribed supplementary thyroxine in the present study. In addition, the basal metabolic rate (BMR) was measured in 13 out of 24 patients and in eight of them it was low (under -15%). Serum thyroid hormone concentrations improved after administration of thyroxine. However, improvement of the BMR was not obtained after one month of supplementary therapy. EEG after administration showed an increase in the power spectra of the occipital alpha 2 band (10.0-12.8 Hz) and beta 1 band (13.0-19.8 Hz), and a decrease in that of the theta band (4.0-7.8 Hz). The interpeak latency from wave I to wave V in the ABR was normalized after administration. These results suggest that supplementary therapy with thyroxine may be necessary in patients with hypothyroidism induced by anticonvulsants.

Thyroid disease in pustulosis palmoplantaris

An increased frequency of thyroid autoantibodies has been reported in patients with palmar and plantar pustulosis (PPP). This study was undertaken to determine the frequency and type of thyroid disease in 32 patients with this disease compared with a control group. Thyroid disease was demonstrated in 53% of the patients with PPP as compared to 16% in the matched control group. Fourteen patients with PPP had an enlarged thyroid and in six there were thyroid autoantibodies. There appears to be an increased incidence of goitre and thyroid autoantibodies in PPP with a decrease in the level of the thyroid hormones.

Cutaneous and immunologic reactions to phenytoin

Phenytoin (diphenylhydantoin; Dilantin) is a highly effective and widely prescribed anticonvulsant and antiarrhythmic agent. Since 1938 it has been invaluable in the treatment of grand mal and psychomotor epilepsy. Hydantoin derivatives have been used medicinally for more than a half-century. In recent years dermatologists have broadened the indications for phenytoin use to include recessive dystrophic epidermolysis bullosa, linear scleroderma, and pachyonychia congenita. In spite of widespread use and popularity, it is interesting that the frequency of complications relating to drug therapy remains low, relatively speaking. Nevertheless, a broad spectrum of cutaneous and immunologic reactions to phenytoin have been reported. These range from tissue proliferative syndromes (side effects), drug hypersensitivity syndromes (allergic effects), and a possible linkage with lymphoma (idiosyncratic effects). Therapeutic and toxic reactions to this commonly prescribed drug are comprehensively reviewed, analyzed, and summarized in this monograph.

Serum thyroglobulin in chronic renal failure--effects of haemodialysis

The influence of chronic renal failure (CRF) on serum thyroglobulin concentration (Tg) was investigated in 37 patients (29 on haemodialysis) and compared with results obtained from matched controls. Serum Tg did not differ significantly between CRF patients not on haemodialysis: median 24.1 micrograms/l, (range 2.5-47.0) and controls: median 23.6 micrograms/l, (range 2.1-53.0). Patients on haemodialysis had a significantly lower serum Tg level: median 11.4 micrograms/l (range 2.1-54.0) compared to controls (p less than 0.01) but no change in serum Tg level could be demonstrated after a single haemodialysis. A possible explanation for the low serum Tg level in patients with CRF on haemodialysis is decreased production parallelling the decreased production rate of T4 and T3. Since CRF patients not on haemodialysis had an unchanged serum Tg level compared to controls, haemodialysis was associated with small changes in serum Tg level, and since none of the patients had a serum Tg value above the upper reference limit we conclude that these changes were not of a magnitude likely to cause misinterpretation of results in routine clinical situations.

Carbamazepine (Tegretol) inhibits in vivo iodide uptake and hormone synthesis in rat thyroid glands

Decreased serum concentrations of T3 and T4 occur in patients treated with the anticonvulsant drug carbamazepine (CBZ), but with rare exception, these patients remain euthyroid. The mechanism that accounts for diminished hormone levels is unknown, and our objective was to study the direct effect of CBZ on iodide uptake and hormone synthesis in thyroid glands of CBZ-treated and pair-fed control rats. Chronic ingestion (per os) of CBZ in male rats reduced the four hour thyroid 131I-iodide uptake by approximately 60%. This inhibition occurred after the animals had received sufficient CBZ to attain plasma CBZ concentrations of 0.8 microgram/ml. Continued treatment with CBZ ranging from 560 to 800 mg/kg/day for 14 days did not result in further inhibition of iodide uptake even though the plasma CBZ concentrations had increased 6-20 fold. No inhibition of iodide uptake was apparent when the animals initially received CBZ ranging from 40 to 152 mg/kg body weight for 22 days when there were no detectable levels of plasma CBZ. Overall growth rates of CBZ-treated rats were slightly (6-10%) less than the pair-fed control animals. Plasma T4 concentrations were reduced by 18% (p less than 0.05) in the CBZ-fed animals, while T3 concentrations were diminished by 53% (p less than 0.01). CBZ appeared to alter thyroidal iodide transport because the thyroid:plasma iodide ratios were decreased by 26% in the drug-treated rats. The distribution of radioiodine in thyroidal iodoamino acids was essentially the same in both groups of rats but the absolute quantities of radioiodine were more than 2.5 times greater in the control rats. CBZ failed to inhibit peroxidase-catalyzed iodide and guaiacol oxidation in vitro. No differences in thyroid gland morphology were noted in the two groups of animals, but weights of the glands from the CBZ-fed animals increased by 25% after 42 days. It is concluded that CBZ, or its metabolites, has a direct inhibitory effect on iodide utilization and hormone synthesis by the thyroid gland.