The role of laboratory medicine in the diagnosis of the hyperthyroidism.

Hyperthyroidism is a clinical condition characterized by inappropriately high synthesis and secretion of thyroid hormones by the thyroid gland. It has multiple aetiologies, manifestations and potential therapies. Graves' disease is the most common form of hyperthyroidism, due to the production of autoantibodies against thyrotropin receptor, capable of over-stimulating thyroid function. A reliable diagnosis of hyperthyroidism can be established on clinical grounds, followed by the evaluation of serum thyroid function tests (thyrotropin first and then free thyroxine, adding the measurement of free triiodothyronine in selected specific situations). The recent guidelines of both the American and European Thyroid Associations have strongly recommended the measurement of thyrotropin receptor autoantibodies for the accurate diagnosis and management of Graves' disease. If autoantibody test is negative, a radioiodine uptake should be performed. Considering the most recent laboratory improvements, binding assays can be considered the best first solution for the measurement of thyrotropin receptor autoantibodies in diagnosis and management of overt cases of Graves' disease. In fact, they have a satisfactory clinical sensitivity and specificity (97.4% and 99.2%, respectively) being performed in clinical laboratories on automated platforms together with the other thyroid function tests. In this setting, the bioassays should be reserved for fine and complex diagnoses and for particular clinical conditions where it is essential to document the transition from stimulating to blocking activity or vice versa (e.g. pregnancy and post-partum, related thyroid eye disease, Hashimoto's thyroiditis with extrathyroidal manifestations, unusual cases after LT4 therapy for hypothyroidism or after antithyroid drug treatment for Graves' disease). Undoubtedly, technological advances will help improve laboratory diagnostics of hyperthyroidism. Nevertheless, despite future progress, the dialogue between clinicians and laboratory will continue to be crucial for an adequate knowledge and interpretation of the laboratory tests and, therefore, for an accurate diagnosis and correct management of the patient.

Anti-glutamic acid decarboxylase antibody in Graves' disease is a possible indicator for the unlikelihood of going into remission with antithyroid agents.

The prevalence and titer of glutamic acid decarboxylase antibody (GADAb) in type 1 diabetes mellitus (T1DM) has been reported to be higher in patients with autoimmune thyroid diseases (AITD) than those without them. However, we have no data about the influence of GADAb on AITD. We therefore studied the clinical characteristics of Graves' disease (GD) with GADAb in order to clarify the influence of GADAb on GD. Twelve GD patients with GADAb were enrolled and were compared to 40 GD patients without DM. The male to female ratio and age of onset of GD showed no statistical difference. The titer of TSH receptor antibody (TRAb) at the onset of GD was similar in both groups. Initial treatment with methimazole (MMI) was started in all patients with GADAb but radioactive iodine (RI) therapy was carried out in five patients because of adverse effects of MMI or poor control of hyperthyroidism. The initial titer of TRAb was significantly lower in patients treated with MMI alone compared to that in RI treated patients but none of the patients treated with MMI alone went into remission after more than 3-years of follow up. We also compared these GADAb-positive patients with 14 patients with diabetes mellitus who had matched clinical features. The number of diabetic patients who remained in possible remission was significantly higher than that of GADAb-positive patients (5 in 14 vs 0 in 12). Moreover, the rate of remission in the diabetic patients was no different from that of 21 control patients without diabetes followed for more than 7 years (5 in 14 vs 7 in 21). These data suggested that GADAb-positive patients are unlikely to go into remission with antithyroid agents. Therefore, definitive therapies might be preferable for the initial treatment of GADAb-positive patients.

[The surgical treatment of Graves' disease]. / Chirurgische behandeling van de ziekte van Graves.

A man aged 80 and three women aged 66, 26, and 39 years respectively, underwent surgery for Graves' disease. The first woman had pneumonia and experienced thyrotoxic storm. Euthyroidism was restored with antithyroid drugs (ATD) and thyroidectomy was performed as ablative treatment for hyperthyroidism. The man presented with thyrotoxicosis and had severe Graves' ophthalmopathy. After euthyroidism was restored with ATD, he underwent subtotal thyroidectomy. The second woman presented with severe thyrotoxicosis but was allergic to ATD. She was treated with iodine and beta-blockers after which subtotal thyroidectomy was done as an ablative procedure. Medical treatment for hyperthyroidism failed in the last patient and, as she had experienced severe psychological disturbances during a previous relapse, she too chose surgery as a definitive treatment option. In two patients the postoperative course was complicated by early hypocalcaemia and one of these patients experienced temporary recurrent laryngeal nerve paralysis. Surgery has a limited role in the treatment of Graves' disease. In pregnant women with severe ATD-resistant thyrotoxicosis, surgery is the only treatment option, while in patients with Graves' orbitopathy surgery may be preferable because of its neutral and perhaps even beneficial effects on eye symptoms. Large goitre size and thyroid nodules are concomitant reasons for choosing surgery, as are allergy to ATD and patients' preference. Lastly, in patients who have suffered from severe thyrotoxicosis, surgery provides rapid and definitive treatment. Early morbidity following surgery is common and should be discussed with the patient.

Occurrence of antineutrophil cytoplasmic antibodies and associated vasculitis in patients with hyperthyroidism treated with antithyroid drugs: A long-term followup study.

OBJECTIVE: To test whether antineutrophil cytoplasmic antibodies (ANCA) and ANCA-associated vasculitis (AAV) are not only induced during treatment with antithyroid drugs, but can also become evident when medication has been ceased, possibly after years. METHODS: Patients who visited our hospital for the treatment of hyperthyroidism were included (n = 207). Treatment consisted of antithyroid medications, radioactive iodide, thyroidectomy, or a combination of these treatment options. Patients were retested 3-6 years later to evaluate long-term effects of antithyroid drugs. Patients were tested for the presence of ANCA and, if positive, evaluated for the presence of AAV. RESULTS: Of 209 patients with hyperthyroidism, 12 patients (6%) were positive for myeloperoxidase- (MPO-), proteinase 3-, or human leukocyte elastase-ANCA. Seventy-seven of 209 patients were retested; 1 patient who had not been treated with antithyroid drugs had developed MPO-ANCA. In 3 of 6 patients previously positive, ANCA could still be detected. The presence of ANCA was highly associated with treatment with antithyroid drugs (odds ratio 11.8 [95% confidence interval 1.5-93.3]). Of 13 patients with a positive ANCA result on enzyme-linked immunosorbent assay, AAV with glomerulonephritis was diagnosed in 4 (31%). CONCLUSION: The presence of ANCA with or without vasculitis is associated with previous treatment with antithyroid drugs, possibly after years.

Anti-thyroid thioureylenes in the treatment of psoriasis.

Psoriasis is a common skin disorder associated with significant morbidity. Many agents are used in the medical management of this debilitating condition with the newer anti-cytokine agents being the most recent addition to the pharmacological armamentarium to battle the disorder. Cost concerns are very important with the newer "biologic" treatments costing in excess of 10,000 US dollars annually. The need for cheaper, orally administered agents is therefore imperative. This paper addresses the potential role of anti-thyroid thioureylenes, propylthiouracil and methimazole, in the treatment of psoriasis and reviews the possible mechanism of action of these drugs in this disorder. It is hypothesized that the beneficial effect of anti-thyroid thioureylenes in psoriasis is linked to their effect as anti-proliferative agents as reflected by significant decrease in markers of cellular proliferation such as proliferative cell nuclear antigen in biopsy specimens after treatment with these drugs. Propylthiouracil has been shown to bind to the hepatic T 3 receptor and it is possible that propylthiouracil (6-n-propyl-2-thiouracil) binding to the ligand-binding site normally occupied by T 3 impairs transcription by inactivating the effect of T 3 as well as by squelching retinoic X receptor heterodimer formation with other receptors of the steroid receptor superfamily such as the peroxisome proliferator-activated receptor, retinoic acid receptor and vitamin D receptors.

Methimazole protects from experimental autoimmune uveitis (EAU) by inhibiting antigen presenting cell function and reducing antigen priming.

Methimazole (methyl-mercapto-imidazole, MMI), a compound used clinically in therapy of Graves' thyroiditis, was found to inhibit development of several autoimmune diseases in animal models. It was suggested on the basis of in vitro data that inhibition is through down-regulation of interferon-gamma (IFN-gamma)-induced expression of major histocompatibility complex class I and class II molecules. Here, we investigate the effect of MMI on experimental autoimmune uveoretinitis (EAU) and study its mechanism(s). Treatment of EAU with MMI administered in drinking water inhibited induction of the disease and associated antigen (Ag)-specific proliferation and cytokine production by draining lymph node cells (LNCs). The treatment was protective only if administered during the first but not during the second week after immunization, suggesting an effect on the induction phase of EAU. It is interesting that MMI inhibited disease in IFN-gamma knockout mice, indicating that the in vivo protective effect is IFN-gamma-independent. Flow cytometric analysis of draining LNCs extracted 5 days after immunization showed that MMI partly to completely reversed the increase in Mac-1(+)/class I(+)/class II(+) cells induced by immunization and reduced the proportion of B7-1 and CD40-positive cells, suggesting a deficit in the Ag-presenting cell (APC) population. APC from untreated mice largely restored antigen-specific proliferation of MMI-treated LNCs. We suggest that MMI inhibits EAU at least in part by preventing the recruitment and/or maturation of APC, resulting in reduced generation of Ag-specific T cells.

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a target glycoprotein in drug-induced thrombocytopenia.

Drug-induced immune thrombocytopenia (DITP) is a serious complication of drug treatment. Previous studies demonstrated that most drug-dependent antibodies (DDAbs) react with the platelet membrane glycoprotein (GP) complexes IIb/IIIa and Ib/IX/V. We analyzed the sera from 5 patients who presented with DITP after intake of carbimazole. Notably, thrombocytopenia induced by carbimazole was relatively mild in comparison to patients with DITP induced by quinidine. The sera reacted with platelets in an immunoassay on addition of the drug. In immunoprecipitation experiments with biotin-labeled platelets and endothelial cells, reactivity with the platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) could be demonstrated, whereas neither GPIIb/IIIa nor GPIb/IX was precipitated in the presence of the drug. These results could be confirmed by GP-specific immunoassay (MAIPA) using monoclonal antibodies (mabs) against PECAM-1. In addition, the binding of DDAbs could be abolished by preincubation with soluble recombinant PECAM-1. Carbimazole-dependent antibodies showed similar reactivity with platelets carrying the Leu(125) and Val(125) PECAM-1 isoforms, indicating that this polymorphic structure, which is located in the first extracellular domain, is not responsible for the epitope formation. Binding studies with biotin-labeled mutants of PECAM-1 and analysis of sera with mabs against different epitopes on PECAM-1 in MAIPA assay suggested that carbimazole-dependent antibodies prominently bound to the second immunoglobulin homology domain of the molecule. Analysis of 20 sera from patients with quinidine-induced thrombocytopenia by MAIPA assay revealed evidence that DDAbs against PECAM-1 are involved in addition to anti-GPIb/IX and anti-GPIIb/IIIa. We conclude that PECAM-1 is an important target GP in DITP. (Blood. 2000;96:1409-1414)

Neutropenia and anaemia due to carbimazole-dependent antibodies.

Carbimazole-dependent antibodies to erythrocytes were detected in the sera of three anaemic patients who had been treated with carbimazole for hyperthyroidism. By the use of Rhnull-typed erythrocytes, we could show that some of these were directed against the proteins of the Rh complex. Carbimazole-dependent antibodies eluted from erythrocytes showed no binding to other blood cells. One patient also presented with neutropenia and mild thrombocytopenia. Additional carbimazole-dependent antibodies against the neutrophil-specific Fcgamma receptor IIIb (FcgammaRIIIb, CD16b) and the broadly expressed platelet endothelial cell adhesion molecule 1 (PECAM-1; CD31) were detected in this patient's serum. Surprisingly, the PECAM-1-reactive drug-dependent antibodies were also detectable in the sera of the other two patients with normal leucocyte and platelet counts. We assume that carbimazole can induce cell lineage-specific drug-dependent antibodies that cause cytopenia and also drug-dependent antibodies against the broadly expressed PECAM-1 molecule that may cause mild but not severe cytopenia.

Leukocytoclastic vasculitis: a rare manifestation of propylthiouracil allergy.

OBJECTIVE: To report a case of leukocytoclastic vasculitis as a manifestation of propylthiouracil allergy. METHODS: We present the history, findings on physical examination, and results of laboratory evaluation in a 25-year-old woman. Associated reports from the literature are reviewed. RESULTS: The patient, with a history of Graves' disease, was referred for evaluation of a purpuric rash on the pinnas and buttocks bilaterally. Findings included exophthalmos and bilateral goiter with neck bruits. She was biochemically hyperthyroid. Biopsy of the skin lesions revealed leukocytoclastic vasculitis. Propylthiouracil therapy was discontinued, and prednisone was prescribed. Treatment with radioactive iodine resulted in appreciably diminished skin lesions and reduction in the size of the thyroid gland, but thyroxine and triiodothyronine levels increased. Administration of a second, higher dose of radioactive iodine with concomitant lithium carbonate resulted in clinical and biochemical improvement. Six months after initial assessment, the rash had resolved, and the patient's free thyroxine value had normalized, although the thyrotropin level was still suppressed. CONCLUSION: Leukocytoclastic vasculitis, although rarely seen as a manifestation of propylthiouracil allergy, has been reported in the medical literature and should be considered in the differential diagnosis of patients with a vasculitic rash. Treatment consists of discontinuation of the offending medication and administration of a corticosteroid and, occasionally, cyclophosphamide or plasmapheresis.

Preserved activation of thyrotropin receptor antibody to stimulate thyroid function despite long-term treatment in euthyroid patients with Graves' disease.

Clinical evaluation was conducted to ascertain whether thyrotropin receptor antibody (TRAb) in the normal range may still be involved in the regulation of thyroid function after prolonged treatment for Graves' disease. All patients (n = 33) were treated with antithyroid drugs for an average of 10.6 years and were under euthyroid conditions in which normal blood levels of tri-iodothyronine (T3) were significantly correlated with blood thyrotropin (TSH) levels, but not with titers of TRAb. A significant correlation was observed between TRAb titer and thyroid-stimulating antibody (TSAb) activity. In contrast, this correlation was not found in normal subjects. After administration of T3 (75 microg daily for 8 days), the patients showed increased levels of T3 with concomitant suppression of TSH levels. Under these conditions, linear regression analysis showed significant correlations of TRAb titer and TSAb activity with 24-h thyroid radioiodine uptake (r = 0.641 and 0.621 respectively, P < 0.01), in contrast to declining blood thyroxine levels. Moreover, the immunoglobulin G (IgG) of the patients precipitated to a greater extent than IgG from normal subjects a peptide consisting of the amino acid sequence near the terminus of the human TSH receptor. These findings indicated that TRAb at normal levels possessed significant unremitting activities on thyroid function despite long-term treatment in euthyroid patients with Graves' disease.

[Theoretical aspects of the treatment with antithyroid drugs]. / Aspects théoriques du traitement par les antithyroïdiens.

Antithyroid drugs (thionamides such as carbimazole and its active metabolite methimazole, and propyl thiouracile) are taken up by the thyroid gland just as the other anions similar to iodide (perchlorate, thiocyanate, pertechnetate). Their target is the thyroid peroxidase. They block the iodation of tyrosine residues and the coupling of iodotyrosines into iodothyronines. However, beyond the inhibition of thyroid hormone synthesis, antithyroid drugs appear to have the capacity of interfering with the immunological abnormalities involved in Graves' hyperthyroidism: they cure 50% of the patients provided they are maintained for at least 12 months and they significantly decrease the titers of antithyroid antibodies in most of the patients. Potential immunomodulatory effects of antithyroid drugs seem to involve thyroid depletion of iodine which might reduce antigen expression, and scavenging of reactive free radicals generated from oxygen and/or iodide during peroxidation. A direct toxic effect of thionamides on immuno-competent cells seems unlikely. Whatever the mechanisms, more accurate elucidation of the immunomodulatory action of antithyroid drugs might contribute to a better understanding of the thyroid-immune derangements involved in the initiation or perpetuation of Graves' hyperthyroidism.

Immunological effects of Graves' disease therapy.

Graves' disease is caused by thyroid stimulating antibodies and is accompanied by other autoimmune phenomena predisposing ultimately towards hypothyroidism. Antithyroid drugs directly alter the natural history of the condition, causing a remission in 50% of cases; part of this is likely to be due to their immunomodulatory effect. Surgery and radioiodine treatment are also accompanied by immunological changes which may affect outcome. In particular, some cases of hypothyroidism may be the result of a hastening of the natural progression to destructive thyroiditis.

Evidence for an effect of antithyroid drugs on the natural history of Graves' disease.

In the United Kingdom, about half the patients with Graves' disease who are given antithyroid drugs are still in remission one year after treatment is stopped. The most widely held view is that such remission rates are due only to the biochemical effects of the drugs, the disease either spontaneously remitting or abating when the immune system is no longer subject to the stimulatory effects of excessive thyroid hormone. We review here the accumulating evidence against both of these alternatives. In contrast, there is now a large body of work which shows that thyrotrophin receptor antibody levels, central to the aetiology of Graves' hyperthyroidism, fall during antithyroid treatment and that remission may be related to this fall in a fashion which is dependent on the dose and duration of treatment. This immunosuppressive effect is supported by experimental data and on the basis of these results we propose that antithyroid drugs may modify the natural history of Graves' disease and contribute to the remission which occurs in a proportion of treated patients.

In vitro immunoreactivity to propylthiouracil, methimazole, and carbimazole in patients with Graves' disease: a possible cause of antithyroid drug-induced agranulocytosis.

Studies of in vitro immunoreactivity to propylthiouracil (PTU), methimazole (MMI), and carbimazole (CARB), as assessed by peripheral blood lymphocyte transformation and 2 antibody tests, were carried out in 12 patients with Graves' hyperthyroidism who had developed agranulocytosis during treatment with PTU (11 patients) or CARB (1 patient) from 1 week to 10 yr earlier. Significant lymphocyte transformation responses to antithyroid drugs (stimulation indices greater than mean +/- 2 SD for normal subjects) were found in 5 of 6 patients tested, in 1 patient to PTU only, in 3 patients to MMI only, and in 1 patient to both PTU and MMI, but in none of 10 patients currently being treated with PTU who did not develop agranulocytosis. Circulating antibodies causing neutrophil agglutination in the presence of antithyroid drugs were demonstrated, using the indirect Coombs test, in 5 of 7 patients tested, in 2 patients to PTU only, in 3 patients to CARB only and in 1 patient (the only one tested with MMI) to PTU and MMI. Lymphocyte transformation and antibody tests to PTU were both carried out in 6 patients. Of these, both tests were positive in one patient, both negative in 3 patients, and 1 negative and 1 positive in 2 patients. In the 1 patient in whom both tests were carried out with CARB (patient 3), tests were negative, whereas in the 1 patient in whom both tests were carried out with MMI (patient 3), 1 test was positive, whereas the other was negative. Thus, in patients in whom both tests were carried out using the same drug, correlation between lymphocyte transformation responses and the detection of neutrophil antibodies was found in 5 of 6 cases. Antibodies reactive with neutrophils were also detected in 2 of the 5 patients tested using an enzyme-linked immunosorbent assay. In this test antibodies to PTU or MMI were not demonstrated. Possible mechanisms for the neutrophil depression in relation to these findings are discussed. It is concluded that patients with Graves' disease may be prone to develop this complication of antithyroid drug therapy because of underlying immunological abnormalities.