Studies of thyroid hormone and methimazole levels in patients with Graves' disease on a standardized anti-thyroid drug regimen

Refractory Graves' Disease in an Adolescent Successfully Treated With Cholestyramine and Subsequent Thyroidectomy

Graves' disease is the most common form of hyperthyroidism in children and adolescents. There are three primary lines of treatment for Graves' disease: antithyroid drugs (ATDs), thyroidectomy, and radioactive iodine. Ideally, patients should be rendered euthyroid before surgery to minimize complications. Here, we report on a 14-year-old girl with severe Graves' disease refractory to conventional treatments despite maximal therapy over 18 months. The patient received two types of ATDs, beta-blockers, and different courses of steroids; however, her thyroid function tests remained high. She was then given an adjunctive four-week course of cholestyramine, to which she responded well and became euthyroid. Subsequently, a thyroidectomy was performed without complications. Cholestyramine is an effective adjunctive treatment for refractory Graves' disease in adolescents.

Thyroid Storm Presenting as Psychosis

Thyroid storm is a life-threatening endocrine emergency with an incidence rate of 1% to 2%. It is a systemic condition of excessive thyroid hormone production and release leading to thermoregulatory, adrenergic, neuropsychiatric, cardiovascular, and abdominal manifestations. Although it is a rare condition, it carries a significant mortality rate. Hence, knowing the common and uncommon presentations of thyroid storm is important for its prompt diagnosis and treatment. In this article, we present an unusual case of a young woman who presented with psychosis as the manifesting symptom of thyroid storm. She did not respond adequately to conventional medical treatment, requiring plasmapheresis and a definitive thyroidectomy, which ultimately led to the return of patient’s baseline mental status and a dramatic recovery.

Antithyroid Drug Therapy for Graves' Disease and Implications for Recurrence

Graves' disease (GD) is the most common cause of hyperthyroidism worldwide. Current therapeutic options for GD include antithyroid drugs (ATD), radioactive iodine, and thyroidectomy. ATD treatment is generally well accepted by patients and clinicians due to some advantages including normalizing thyroid function in a short time, hardly causing hypothyroidism, and ameliorating immune disorder while avoiding radiation exposure and invasive procedures. However, the relatively high recurrence rate is a major concern for ATD treatment, which is associated with multiple influencing factors like clinical characteristics, treatment strategies, and genetic and environmental factors. Of these influencing factors, some are modifiable but some are nonmodifiable. The recurrence risk can be reduced by adjusting the modifiable factors as much as possible. The titration regimen for 12-18 months is the optimal strategy of ATD. Levothyroxine administration after successful ATD treatment was not recommended. The addition of immunosuppressive drugs might be helpful to decrease the recurrence rate of GD patients after ATD withdrawal, whereas further studies are needed to address the safety and efficacy. This paper reviewed the current knowledge of ATD treatment and mainly focused on influencing factors for recurrence in GD patients with ATD treatment.

Refractory Graves' Disease Successfully Cured by Adjunctive Cholestyramine and Subsequent Total Thyroidectomy

The three major forms of treatment for Graves thyrotoxicosis are antithyroid drugs, radioactive iodine therapy and thyroidectomy. Surgery is the definitive treatment for Graves thyrotoxicosis that is generally recommended when other treatments have failed or are contraindicated. Generally, thyrotoxic patients should be euthyroid before surgery to minimize potential complications which usually requires preoperative management with thionamides or inorganic iodine. But several cases of refractory Graves' disease have shown resistance to conventional treatment. Here we report a 40-year-old female patient with Graves' disease who complained of thyrotoxic symptoms for 7 months. Her thyroid function test and thyroid autoantibody profiles were consistent with Graves' disease. One kind of thionamides and β-blocker were started to control her disease. However, she was resistant to nearly all conventional medical therapies, including β-blockers, inorganic iodine, and two thionamides. She experienced hepatotoxicity from the thionamides. What was worse is her past history of serious allergic reaction to corticosteroids, which are often used to help control symptoms. A 2-week regimen of high-dose cholestyramine improved her uncontrolled thyrotoxicosis and subsequent thyroidectomy was successfully performed. In conclusion, cholestyramine could be administered as an effective and safe adjunctive agent for preoperative preparation in patients with severe hyperthyroid Graves's disease that is resistant to conventional therapies.

Role of colestipol in the treatment of hyperthyroidism

The enterohepatic circulation of thyroxine (T4) and triiodothyronine (T3) is higher in thyrotoxicosis. Bile-salt sequestrants bind iodothyronines and thereby increase their fecal excretion. We, therefore, evaluated the effect of colestipol-hydrochloride administration on clinical and biochemical indices of patients with hyperthyroidism. In a prospective, controlled trial, ninety-two adult volunteers with Graves' disease, toxic autonomous nodule or toxic multinodular goiter were randomly assigned into the following treatment protocols: Group 1, 30 mg of methimazole (MMI) and 20 g of colestipol-hydrochloride (COL) daily; Group 2, 30 mg of MMI daily; and Group 3, 15 mg of MMI 20 g of COL daily. The patients were further classified into Group A, severe hyperthyroidism (baseline levels of total T3 (TT3) > or =5 nmol/l) and Group B, mild to moderate thyrotoxicosis (baseline levels of TT-3<5 nmol/l). Crook's clinical index, serum free T4 (FT4), TT3 and thyroid stimulating hormone (TSH) levels were determined before (WO), following one week (W1) and two weeks (W2) of treatment. Serum TT3 level decreased (mean+/-SE) at W1 by 40.8+/-2.6% of WO in Group1 and by 29.2+/-2.4% in Group 2 (p<0.001), and down further to 47.8+/-3.0% at W2 in Group 1, and 40.6+/-2.8% in Group 2 (p=0.01). Serum FT4 level decreased (mean+/-SE) from WO to W1 by 31.7+/-2.7% in Group 1 and by 16.2+/-3.1% in Group 2 (p=0.005), and down to 49.1+/-2.8% of WO at W2 in Group 1 and to 38.7+/-3.5% in Group 2 (p=0.07). In sub groups B COL was not effective in reducing thyroid hormone levels nor in ameliorating the clinical status of the patients. However, in Group A3 COL lowered FT4 (p=0.001) and TT3 (p=0.05) levels as compared to group A2. At W2 the clinical hyperthyroidism score improved faster in Group A1 (p<0.001) and Group A3 (p=0.012) as compared to the control Group A2. In conclusion, COL is an effective and well tolerated adjunctive agent in the treatment of hyperthyroidism. Its main effect is in severe cases of thyrotoxicosis, and in the first phase of treatment. As adjunctive COL treatment in hyperthyroidism allows reducing MMI dosage it may decrease the rate of dose dependent MMI side effects.

Management guidelines for hyperthyroidism

Anti-thyroid drugs, surgery and radioiodine all represent effective forms of treatment for Graves' hyperthyroidism. There is, however, little consensus regarding the treatment of choice for specific cases. This lack of consensus prompted the development of guidelines for good practice in the management of hyperthyroidism for the United Kingdom. This chapter describes the process of development of this United Kingdom consensus statement, and associated audit measures, and highlights outstanding contentious issues in the management of Graves' hyperthyroidism.

Response to methimazole in Graves' disease. The European Multicenter Study Group

OBJECTIVE

A variety of regimens continue to be used in the treatment of Graves' disease with antithyroid drugs. We have investigated the factors which determine the initial response to methimazole (time until euthyroidism is achieved) in Graves' disease.

PATIENTS

Five hundred and nine patients with Graves' disease in different European countries with normal and subnormal iodine supply. Patients were randomized to treatment with either 10 or 40 mg of methimazole per day for one year, with levothyroxine supplementation as required to maintain euthyroidism. Investigations were carried out before treatment and at 3 and 6 weeks and 3, 6, 9 and 12 months.

MEASUREMENTS

Response was assessed by serial measurements of serum thyroid hormones. TSH receptor antibodies, thyroid autoantibodies and urinary iodide excretion were measured centrally. Twenty-minute thyroid uptake was measured by standard techniques. Data were collected and analysed centrally. Standard techniques as well as a stepwise logistic regression model were used to examine the relations between methimazole dose, age, goitre size, presence of endocrine eye signs, thyroid hormone levels, urinary iodide excretion, thyroid uptake, index of disease severity (Crooks), presence of TSH receptor antibodies and duration of the hyperthyroid phase.

RESULTS

Within 3 weeks, 40.2% of patients responded to 10 mg of methimazole and 77.5% responded within 6 weeks. The corresponding figures for 40 mg of methimazole were 64.6 and 92.6%. Significant associations were found between duration of hyperthyroidism and the following variables: goitre size, urinary iodide excretion, methimazole dose, presence of TSH receptor antibodies (TBIAb), index of disease severity (Crooks) and pretreatment thyroid hormone levels. Response to methimazole was delayed in patients with large goitres, iodine excretion of > or = 100 micrograms/g creatinine, high pretreatment thyroid hormone levels, elevated levels of TBIAb and treatment with only 10 mg of methimazole. In the 10-mg group, 46% of patients were euthyroid within 3 weeks when urinary iodide was < 50 microgram/g of creatinine, and only 27% when iodide was above 100 micrograms/g. By stepwise logistic regression, the main factors for the response to methimazole were daily dose, pretreatment T3 levels, and goitre size.

CONCLUSION

Methimazole dose, pretreatment serum T3 levels, and goitre size are the main determinants of the therapeutic response to methimazole in Graves' disease, at least in areas comprising low, subnormal and normal iodine supply.

The management of hyperthyroidism

Although effective treatments for hyperthyroidism are available, none is perfect. Particularly with respect to Graves' disease, what is needed is a therapy directed at modulating the disease process itself rather than merely reducing the synthesis and secretion of thyroid hormones in the hope that the underlying Graves' disease will remit. Greater understanding of the pathogenesis of Graves' disease, resulting from cloning of the thyrotropin receptor and better knowledge of the interactions between these receptors or other thyroid antigens and the immune system, may lead to such treatment. Broad-spectrum immunosuppression, with all its side effects, is not the answer; more focused therapies to inhibit the immune response to specific thyroid antigens may represent the treatment of the future. Meanwhile, radioiodine therapy is the most effective and convenient method of achieving long-term control of hyperthyroidism, although at the cost of hypothyroidism in many patients.

Modulation of the IL-2 production defect in vitro in Graves' disease

IL-2 production by mitogen-induced peripheral blood mononuclear cells was reported to be reduced in several autoimmune diseases, including Graves' disease (GD). This production defect in hyperthyroid GD was restored to normal by antithyroid drug therapy or during remission. However, its underlying mechanism and role in the autoimmune process are still uncertain. The present study was undertaken in order to screen the in vitro IL-2 generating system for putative factors responsible for its failure, and to see to what extent this was reversible. Thyroid hormone or antithyroid drugs had no effect on IL-2 production in vitro. Cultures were found to be free of soluble inhibitors of IL-2 production or action. IL-1 deficiency as a cause of the IL-2 defect was ruled out; rather, Graves' adherent cells were found to be activated in being capable of secreting large amounts of IL-1 and prostaglandin E2 (PGE2). The latter was not found to be responsible for the decreased IL-2 production. IL-2 production by Graves' mononuclears was completely restored to normal by: (i) adherent cell depletion, irradiation or substitution with normal adherent cells; (ii) preincubation of mononuclears for 24-72 h before mitogen stimulation; (iii) the synergistic action of a phorbol ester and a calcium ionophore. These data indicate that inhibition by activated adherent cells accounts for the in vitro IL-2 production defect in GD. This inhibition is not mediated by soluble factors, but probably through direct interaction with the producing cells, and is reversible in rested cultures or through a bypassed signal transduction.

Higher than conventional doses of carbimazole in the treatment of thyrotoxicosis

In order to ascertain whether higher than conventional doses of carbimazole achieve more rapid control of thyrotoxicosis, 30 thyrotoxic patients were alternately allocated into two groups, group 1 (15 subjects) receiving a conventional starting dose of 45 mg orally daily and group 2 (15 subjects) a dose of 100 mg orally. In addition to weekly estimations of serum T4, T3, free T4, free T3 and TSH, the systolic time intervals ratio (STI), a measure of left ventricular contractility, was calculated as an accurate measure of peripheral thyroid hormone activity, the study end-point being a normal STI (0.26-0.32). None of the individuals studied experienced side-effects during the study period. Mean pre-treatment STI values for the two treatment groups were the same at entry (0.20). The mean recovery times for STI was 4.4 weeks (SE 0.3) in the high dose group and 5.9 weeks (SE 0.4) in the low dose group (P = 0.0037). There was a definite trend towards a shorter recovery time for free T3 in the higher dose group (P = 0.057) but no apparent differences for T4, T3 and free T4. Higher than conventional doses of carbimazole may be advisable in the initial treatment of severe thyrotoxicosis.

Production of and response to interleukin-2 in Graves' disease

Interleukin-2 is a lymphokine which is believed to play a central role in the regulation of the immune response. The production of and response to interleukin-2 were determined in hyperthyroid Graves' patients together with thyroid function and serum thyrotropin receptor antibody, a marker of autoimmune activity. Interleukin-2 production by mitogen-induced peripheral blood mononuclears was markedly low in 24 of 29 patients when compared to controls. Five patients in remission had normal values. In nine patients followed during antithyroid drug therapy, interleukin-2 production returned gradually to normal levels within 4-6 months. This rise and the concomitant decrease in serum thyrotropin receptor antibody correlated with the decline in the free thyroxin index. Antithyroid drugs and triiodothyronine had no effect on interleukin-2 production in vitro. Mitogen-activated mononuclears from hyperthyroid Graves' patients did not proliferate as well as the controls in response to interleukin-2. However, seven patients treated with antithyroid drugs and three in remission responded normally. Flow cytometry using anti-Tac antibody revealed that the interleukin-2 receptor density on mononuclears from five patients was low. This parameter was normal in treated patients and those in remission. We conclude that the production of and response to interleukin-2 by peripheral blood mononuclears from hyperthyroid Graves' patients are poor, the latter being due to impaired receptor expression. Both aberrations are restored to normal by antithyroid drug therapy or in remission. The relative roles of the autoimmune process and thyroid function in modulating the interleukin-2 pathway and the question of whether antithyroid drugs act directly or through thyroid inhibition remain to be clarified.

The significance of the initial FT4-index for the management of single daily dose methimazole treatment of hyperthyroidism

Since the effectiveness of 30 mg methimazole in a single daily dose in gaining initial control of hyperthyroidism may depend largely on patient characteristics, 52 patients (34 with diffuse and 18 with nodular goitre) were investigated in an attempt to determine the relative importance of a number of pretreatment variables. Return to normal thyroid hormone levels after 2 to 6 weeks of treatment appeared to be the rule, although eight of these patients formed notable exceptions (6-20 weeks). The individual duration of treatment until achievement of biochemical euthyroidism correlated with the initial free thyroxine index (r = 0.75, P less than 0.001) and the free triiodothyronine index (r = 0.70, P less than 0.001). For patients with a diffuse goitre it was also related to the thyroid volume estimated by ultrasound (r = 0.73, P less than 0.001). According to multiple linear regression analysis however these variables were found to have no independent prognostic value. The decrease in thyroid volume during initial therapy, the nature of the goitre, a medication compliance score and various other patient variables did not correlate with the effect of treatment. In 12 cases perchlorate discharge tests were performed. The results suggest continued hormone synthesis in patients with highly active iodine trapping as an important mechanism of the postponed attainment of euthyroidism.

Induction of circulating activated suppressor-like T cells by methimazole therapy for Graves' disease

Thyrostatic drug treatment of Graves' disease suppresses excessive thyroid hormone synthesis and causes a parallel decrease in serum thyroid autoantibody levels. The mechanism of this immunosuppression is unknown. We studied methimazole-induced immunoregulatory effects prospectively in 14 patients with Graves' disease treated for up to six months. The numbers of circulating activated, HLA-DR-positive T helper/inducer cells decreased gradually, from 8.3+1.7 percent (+SD) to 1.0+1.7 percent (P less than 0.001). HLA-DR-positive T suppressor/cytotoxic cells increased transiently at one month, from 2.0+1.9 percent to 12.6+6.4 percent (P less than 0.001), and returned to 2.9+3.7 percent at six months. Methimazole did not alter the HLA-DR expression of T cells in vitro. In two patients, the helper activity of T cells in inducing autoantibody secretion in vitro was substantially reduced after one month of methimazole treatment. Before treatment, large proportions of thyroid-infiltrating T-cell subsets expressed the activation markers HLA-DR, interferon-gamma, and interleukin-2 receptors, which were partially lost during therapy. Methimazole treatment was accompanied by a gradual reduction in circulating levels of thyrotropin-receptor, microsomal, and thyroglobulin autoantibodies. These results are compatible with the view that methimazole-induced immunoregulation in Graves' disease is mediated by a direct inhibitory effect on thyrocytes. This inhibition is in turn accompanied by marked changes in the proportions of activated T helper-like and T suppressor-like cells. This altered T-cell activation profile reflects, at least in part, the functional suppression of autoantibody production observed in methimazole-treated patients with Graves' disease.

Pharmacokinetics of methimazole in humans

A newly developed method for extracting and measuring methimazole in biological fluids was used to study the pharmacokinetics of methimazole in two euthyroid and eight hyperthyroid subjects. The volume of distribution approximated total body water; the biological half-life was 2-3 h in euthyroid and about 6 h in hyperthyroid patients. Total clearance was lower in hyperthyroid patients than in euthyroid subjects, and it did not increase after thyroid function was normalized. Bioavailability in euthyroid subjects was greater than 1 but only 0.5 in hyperthyroid subjects. The reasons for these observed differences are not known.

Syndrome of persisting thyroid stimulating immunoglobulins and growth promotion of goiter combined with low thyroxine and high triiodothyronine serum levels in drug treated Graves' disease

Among 48 Graves' patients treated with antithyroid drugs there were 8 patients with a further growth of an already enlarged goiter and a persistence of thyroid stimulating immunoglobulins (TSI). TSI activity did not persist in a comparison group of patients with less severe initial symptoms and an uncomplicated course during a similar regimen of drug treatment. Thyrotoxicosis was difficult to control in this subgroup of patients as low serum T4 was accompanied by borderline high T3 levels although TSH in serum remained undetectable. In spite of comparable low doses of antithyroid drugs serum T4 in the complicated group remained significantly lower (58 +/= 15 nmol/I SD vs. 97 +/- 19 nmol/I SD, p less than 0,001) and serum T3 stayed significantly higher (3,66 +/- 0,49 nmol/I SD vs. 2,15 +/- 0,50 nmol/I SD, p less than 0,001) than in the group with uncomplicated treatment. It is discussed that the promotion of goiter growth could be due to growth stimulating antibodies, and that a local intrathyroidal iodide depletion during antithyroid drug treatment might cause the shift from T4 to T3 production in this entity of Graves' patients.

Clinical pharmacokinetics of antithyroid drugs

Organic antithyroid drugs used today include propylthiouracil and the mercaptoimidazolines, carbimazole and methimazole. They can be measured with accuracy and in small quantities in serum by gas-liquid chromatography, high performance liquid chromatography and radio-immunoassay. Bioavailability of these drugs varies from 80 to 95%. During absorption carbimazole, which itself is inactive, is completely converted to methimazole. The total volume of distribution is about 40L for methimazole and around 30L for propylthiouracil, which is about 80% protein-bound, while methimazole is virtually non-protein-bound. Drug transfer across the placenta and into breast milk is also higher for the more lipid-soluble methimazole than for propylthiouracil, which is excreted into breast milk only in small quantities so that no harmful effect to the suckling infant is to be expected. Both drugs are concentrated in the thyroid gland, exerting an effect on intrathyroidal iodine metabolism for periods exceeding those in which serum concentrations can be measured. Less than 10% of both drugs is excreted unchanged in the urine, but detailed metabolic pathways are unknown. The half-life of methimazole is 3 to 5 hours with a total clearance of about 200ml/minute. Propylthiouracil has a half-life of 1 to 2 hours with a clearance of around 120ml/min/m2. Some studies have shown an increased rate of metabolism of anti-thyroid drugs in hyperthyroidism, in particular for methimazole. No reliable information exists regarding pharmacokinetics of these agents in renal and hepatic failure or in children. The clearance of propylthiouracil is unchanged in the elderly. Several mechanisms for the inhibiting effect of these agents on intrathyroidal hormone metabolism have been suggested. In contrast to methimazole, propylthiouracil inhibits the peripheral conversion of thyroxine to triiodothyronine. Preliminary dose-response studies with propylthiouracil suggest a peak therapeutic serum concentration of above 4 micrograms/ml in the treatment of thyrotoxicosis. The choice between the antithyroid drugs is based more upon personal preference and experience than on strict pharmacological principles, as no important differences exist between these drugs with regard to the rate of remission or frequency of occurrence of serious adverse reactions.