Effects of excess iodine administration on thyroid function in euthyroid patients with a previous episode of thyroid dysfunction induced by interferon-alpha treatment

Association of interferon-based therapy with risk of autoimmune diseases in patients with chronic hepatitis C virus infection: A population-based Taiwanese cohort study

Background

Interferon in combination with ribavirin has been the standard of care for chronic hepatitis C virus infection (HCV) for the past few decades. However, its effect on the risk of autoimmune diseases (ADs) among patients with HCV infection remains unclear. We assessed the potential association between interferon-based therapy (IBT) and AD risk in patients with HCV infection.

Methods

This retrospective cohort study identified patients diagnosed with HCV infection between January 1, 2006, and December 31, 2015, from Taiwan’s National Health Insurance Research Database. In total, 16,029 patients with HCV infection who received IBT and 141,214 patients with HCV infection who did not receive IBT were included. Both cohorts were followed up to assess the development of ADs. Hazard ratios (HRs) were calculated using the Cox proportional hazards regression model, which was adjusted for potential confounders.

Results

The median follow-up period for IBT and non-IBT users was 4.53 and 3.34 years, respectively. No significant difference in the risk of overall ADs (adjusted HR [aHR]: 0.96, 95% confidence interval [CI]: 0.81–1.14) or systemic ADs (aHR: 0.88, 95% CI: 0.71–1.10) was noted during the study period. However, a slight increase in the risk of organ-specific ADs was noted among IBT users (incidence rate ratio: 1.33, 95% CI: 1.02–1.72). Furthermore, analysis of AD subgroups revealed a significant increase in the risks of Graves’ disease (aHR: 6.06, 95% CI: 1.27–28.8) and Hashimoto’s thyroiditis (aHR 1.49, 95% CI 1.01–2.21) among IBT users.

Conclusions

IBT use increases the risk of autoimmune thyroid diseases (Hashimoto’s thyroiditis and Graves’ disease) in patients with HCV infection to a greater extent than non-IBT use.

Amiodarone-Induced Thyrotoxicosis Recurrence After Amiodarone Reintroduction

Reintroduction of amiodarone in patients with a history of amiodarone-induced thyrotoxicosis (AIT) is rarely used. To date, the risk of AIT recurrence after amiodarone reintroduction is unpredicted. The aim of the study was to evaluate the risk of AIT recurrence. Retrospectively, from 2000 to 2011, all euthyroid patients with a history of AIT with amiodarone reintroduction were included. Type and severity of the first AIT, amiodarone chronology, and thyroid function evolution after reintroduction of amiodarone were investigated: 46 of 172 patients with AIT history needed amiodarone reintroduction. At first AIT episode, the mean age was 62.2 ± 16 years with male gender predominance; 65% of patients were classified as type 1 AIT. AIT recurred in 14 patients (30%), 12 patients developed hypothyroidism (26%), and 20 patients remained euthyroid (44%). Characteristics of type 1 AIT during the first episode, namely briefer exposure period to amiodarone and longer duration of treatment to normalize thyroid hormones, were predictive of AIT recurrence; 73% of patients (8 of 11) with previous episode of type 1 AIT, who did not receive a preventive thioamide treatment, developed a second episode of AIT. Thioamide preventive treatment could be useful to prevent type 1 AIT recurrence. In conclusion, AIT recurrence after amiodarone reintroduction is 4 times more frequent in patients with type 1 AIT history. Thyroid ablation before amiodarone reintroduction in patients with a history of type 1 AIT is preferred. Preventive thioamide treatment could be suggested in patients with type 1 AIT history pending for surgery.

THE ABSENCE OF THYROID DISEASE IN AN AUSTRALIAN HEPATITIS C COHORT TREATED WITH TRIPLE COMBINATION THERAPY: A PARADIGM SHIFT

OBJECTIVE

To assess the prevalence of thyroid disease in triple combination therapy with interferon (IFN)-α, ribavirin (RBV), and protease inhibitors (boceprevir and telaprevir) for the treatment of chronic hepatitis C virus (HCV) infection in an Australian hepatitis C cohort. Also, to compare with those who received dual RBV and IFN in the past.

METHODS

A preliminary, retrospective, and nested case control study of thyroid disease in patients who underwent triple combination therapy for chronic HCV infection compared with dual therapy at a major tertiary referral hospital center. Fifty-nine patients were treated with such therapy at the Hunter New England Area Hepatitis C Treatment Center. Of these, 38 were treated with boceprevir and 21 with telaprevir. All had genotype 1 HCV infection. The main outcome measures included (1) the prevalence of thyroid disease (TD), including hyperthyroidism and hypothyroidism, and (2) thyroid outcome comparison with patients who had received dual therapy.

RESULTS

There was no case of TD detected for the entire duration of therapy with triple anti-HCV therapy. There was a significant absence of TD in the protease inhibitor-treated group.

CONCLUSION

No case of TD was detected during the treatment of HCV patients with protease inhibitor-based triple therapy. The reasons for this are unclear. Larger studies are necessary to confirm this finding.

Effects of potassium iodide in concentrations of TSH, tT3 and tT4 in serum of subjects with sporotrichosis

The saturated potassium iodide solution (SSKI) as treatment for sporotrichosis may cause hypothyroidism by suppressing the synthesis of thyroid hormones (tT3 and tT4 ) and the iodine excess could lead to thyrotoxicosis. Evaluating the changes in serum levels of TSH, tT3 and tT4 in euthyroid patients with sporotrichosis treated with SSKI. For the selection of euthyroid patients, TSH, tT3 and tT4 concentrations were measured for those adults and children diagnosed with sporotrichosis. Each paediatric patient was administered SSKI orally in increasing doses of 2-20 drops/3 times/day and 4-40 drops/3 times/day in adults. Serum concentrations of TSH, tT3 and tT4 were measured 20 days after started the treatment and 15 days posttreatment. Eight euthyroid patients aged between 2 to 65 years old were included. After 20 days of treatment, two suffered subclinical hypothyroidism, one developed subclinical hyperthyroidism, and one hyperthyroxinaemia euthyroid. At 15 days posttreatment only four patients were evaluated and all serum levels of TSH, tT3 and tT4 were normal. Some euthyroid patients with sporotrichosis can develop hyperthyroidism or subclinical iodine-induced hypothyroidism, during the administration of 3 or 6 g SSKI/day.

Autoimmune and neoplastic thyroid diseases associated with hepatitis C chronic infection

Frequently, patients with hepatitis C virus (HCV) chronic infection have high levels of serum anti-thyroperoxidase and/or anti-thyroglobulin autoantibodies, ultrasonographic signs of chronic autoimmune thyroiditis, and subclinical hypothyroidism, in female gender versus healthy controls, or hepatitis B virus infected patients. In patients with "HCV-associated mixed cryoglobulinemia" (MC + HCV), a higher prevalence of thyroid autoimmune disorders was shown not only compared to controls, but also versus HCV patients without cryoglobulinemia. Patients with MC + HCV or HCV chronic infection show a higher prevalence of papillary thyroid cancer than controls, in particular in patients with autoimmune thyroiditis. Patients with HCV chronic infection, or with MC + HCV, in presence of autoimmune thyroiditis, show higher serum levels of T-helper (Th)1 (C-X-C motif) ligand 10 (CXCL10) chemokine, but normal levels of Th2 (C-C motif) ligand 2 chemokine, than patients without thyroiditis. HCV thyroid infection could act by upregulating CXCL10 gene expression and secretion in thyrocytes recruiting Th1 lymphocytes that secrete interferon-γ and tumor necrosis factor-α. These cytokines might induce a further CXCL10 secretion by thyrocytes, thus perpetuating the immune cascade, which may lead to the appearance of autoimmune thyroid disorders in genetically predisposed subjects. A careful monitoring of thyroid function, particularly where nodules occur, is recommended in HCV patients.

Immunological alterations in hepatitis C virus infection

A higher prevalence of immunological processes has recently been reported in patients with hepatitis C virus (HCV) infection, focusing the attention of physicians and researchers on the close association between HCV and immune disorders. HCV lymphotropism represents the most important step in the pathogenesis of virus-related immunological diseases and experimental, virologic, and clinical evidence has demonstrated a trigger role for HCV both in systemic autoimmune diseases, such as rheumatoid arthritis, Sjögren syndrome, hemolytic anemia and severe thrombocytopenia, and in organ-specific autoimmune diseases, such as autoimmune hepatitis, thyroid disorders and diabetes. This review will outline the principal aspects of such HCV-induced immunological alterations, focusing on the prevalence of these less characterized HCV extrahepatic manifestations.

Thyroid disease in chronic hepatitis C infection treated with combination interferon-α and ribavirin: management strategies and future perspective

OBJECTIVE

Hepatitis C virus (HCV) infection is one of the major epidemics afflicting young people in both developed and developing countries. The most common endocrine disorder associated with this infection, especially in conjunction with interferon-α (IFN-α)-based therapy, is thyroid disease (TD). This review examines the development of TD before, during, and after the completion of treatment with combination IFN-α and ribavirin (RBV) for chronic HCV infection. We also summarize the current understanding of the natural history of the condition and propose management and follow-up guidelines.

METHODS

PubMed was searched up to June 30, 2011 for English-language publications that contained the search terms "hepatitis C virus," "chronic hepatitis C," "HCV," "thyroid disease," "thyroiditis," "autoimmunity," "interferon-alpha," and "ribavirin." Additional publications were identified from the reference lists of identified papers. The included studies were original research publications and included combination IFN-α and RBV use in patients that developed TD.

RESULTS

The prevalence of TD before combination IFN-α and RBV therapy ranges from 4.6 to 21.3%; during therapy, 1.1 to 21.3%; and after therapy, 6.7 to 21.3%. The most common TD is thyroiditis. Thyroid function testing (TFT) frequency and diagnostic criteria for various thyroid conditions are not standardized, and many of the existing studies are retrospective.

CONCLUSION

Patients undergoing this therapy should be assessed with a standardized protocol to appropriately detect and manage developed TD. Based on the currently available literature, we recommend that patients receiving combination interferon-α and RBV therapy undergo monthly thyrotropin (TSH) level testing.

Autoimmune thyroid disorders in hepatitis C virus infection: Effect of interferon therapy

The hepatitis C virus infection represents an important public health problem and is associated with various hepatic and extrahepatic manifestations. Symptoms outside of the liver can occur in multiple organ systems, including hematologic, renal, dermatologic, endocrine, and rheumatologic systems. Among these different organ systems, special attention has focused on the endocrine system because it affects almost every organ in the body. Among the endocrine disorders, thyroid problems are the most common and the thyroid is one of the principal target organs for extrahepatic manifestations in HCV infected patients. In addition, research data suggest that interferon treatment may be associated with immune-mediated thyroid lesions. However, case reports suggest that the response of thyroid extrahepatic manifestations to interferon in patients with chronic HCV is greatly different. The objective of this study was to summarize currently available data on thyroid conditions associated with chronic HCV infection. Moreover, we investigate the incidence of the development of immune mediated thyroid disorders during interferon therapy in these patients.

Hepatitis C virus infection and autoimmune diseases

Hepatitis C virus (HCV) infection is associated with a number of extrahepatic disorders. The most studied conditions associated with HCV are type II mixed cryoglobulinemia and B cell lymphoma. However, many reports suggest that HCV might also be associated with a number of autoimmune disorders, both organ-specific and not organ-specific. Although concomitant treatment of HCV infection is a confounding factor when ascertaining the actual role of HCV in inducing autoimmune disease, a considerable amount of experimental data indicates that HCV is able to subvert the immune system and consequently induce autoimmunity. In the present review, we report a series of observations which associate chronic HCV infection with the onset of autoimmune disorders.

Adverse effects of iodine thyroid blocking: a systematic review

(131)I, when released in a radiological or nuclear accident as happened recently in Fukushima, Japan, may cause thyroid cancer as a long-term consequence. Iodine thyroid blocking (ITB) is known to reduce the risk of developing thyroid cancer. Potential adverse effects of ITB have not been systematically investigated so far. This article summarises the results of a review on adverse effects of ITB based on a systematic literature search in scientific medical databases. A meta-analysis was not performed as identified studies displayed major heterogeneity. The search resulted in 14 articles relevant to the topic, reporting mostly on surveys, ecological and intervention studies. Only one study from Poland focused on effects (both desired and adverse) of an ITB intervention following the Chernobyl accident. All other studies reported on iodine administration in a different context. Overall, the studies did not reveal severe adverse reactions to potassium iodide in the general public. Since ITB is a protective measure only applied in very specific circumstances, scientifically sound studies of adverse effects are scarce and consequently the evidence base is weak. The assessment of adverse effects of ITB relies on indirect evidence from related areas. This study may contribute to ongoing developments in pharmacoepidemiology aiming to better quantify adverse effects of medications and health care interventions including ITB.

Cytokines and HCV-related disorders

Cytokines are intercellular mediators involved in viral control and liver damage being induced by infection with hepatitis C virus (HCV). The complex cytokine network operating during initial infection allows a coordinated, effective development of both innate and adaptive immune responses. However, HCV interferes with cytokines at various levels and escapes immune response by inducing a T-helper (Th)2/T cytotoxic 2 cytokine profile. Inability to control infection leads to the recruitment of inflammatory infiltrates into the liver parenchyma by interferon (IFN)-gamma-inducible CXC chemokine ligand (CXCL)-9, -10, and -11 chemokines, which results in sustained liver damage and eventually in liver cirrhosis. The most important systemic HCV-related extrahepatic diseases--mixed cryoglobulinemia, lymphoproliferative disorders, thyroid autoimmune disorders, and type 2 diabetes--are associated with a complex dysregulation of the cytokine/chemokine network, involving proinflammatory and Th1 chemokines. The therapeutical administration of cytokines such as IFN-alpha may result in viral clearance during persistent infection and reverts this process.

Extrahepatic manifestations of hepatitis C virus infection

Hepatitis C virus may cause hepatic and extrahepatic diseases. Extrahepatic manifestations range from disorders for which a significant association with viral infection is supported by epidemiologic and pathogenetic data, to anecdotal observations without clear proof of causality. This article describes the diagnosis and treatment of these diseases.

HCV-related autoimmune and neoplastic disorders: the HCV syndrome

Hepatitis C virus (HCV) chronic infection may be associated with a great number of both hepatic and extrahepatic manifestations. HCV lymphotropism is responsible for poly-oligoclonal B-lymphocyte expansion, which is the common underlying alteration in a significant percentage of HCV-infected individuals. The consequent production of different autoantibodies and immune-complexes, including cryoglobulins, may lead to organ- and non-organ-specific immunological alterations. Mixed cryoglobulinemia, a small-vessel systemic vasculitis, is characterized by the coexistence of autoimmune and lymphoproliferative alterations; therefore, it represents the prototype of HCV-associated disorders. Moreover, HCV shows an oncogenic potential; several studies support its pathogenetic link with some malignancies, mainly hepatocellular carcinoma and B-cell lymphomas. On the whole, HCV-related disorders present a heterogeneous geographical distribution, suggesting a role of other important genetic and/or environmental cofactors. While the majority of HCV-infected individuals is asymptomatic or may develop only liver manifestations, a significant percentage of them may develop a variable combination of autoimmune lymphoproliferative disorders. The resulting multiform clinico-pathological condition can be termed HCV syndrome. The natural history of HCV syndrome is the expression of multifactorial and multistep pathogenetic process, which usually proceeds from mild, often isolated manifestations to systemic immune-mediated disorders, and less frequently to overt malignancies.

Extrahepatic manifestations of Hepatitis C Virus infection: a general overview and guidelines for a clinical approach

Hepatitis C Virus is associated with a wide series of extrahepatic manifestations. Based on available data the link between the virus and some of these extrahepatic diseases is only suggested and needs further confirmation. Hepatitis C Virus-related lymphoproliferative disorders, whose prototype is mixed cryoglobulinaemia, represent the most closely related extrahepatic manifestations of Hepatitis C Virus. Other Hepatitis C Virus-associated disorders include nephropathies, thyreopathies, sicca syndrome, idiopathic pulmonary fibrosis, porphyria cutanea tarda, lichen planus, diabetes, chronic polyarthritis, cardiopathy and atherosclerosis. A pathogenetic link between Hepatitis C Virus and some extrahepatic manifestations was confirmed by their responsiveness to antiviral therapy, which is now deemed the first therapeutic option to consider. By contrast, there are diseases where treatment with interferon was ineffective or dangerous. The aim of the present paper is to outline the most recent evidence concerning extrahepatic disorders that are possibly associated with Hepatitis C Virus infection. Special emphasis will be given to discussion of the most appropriate clinical approaches to be adopted in order to diagnose, treat (possibly prevent) and follow-up extrahepathic diseases in patients with Hepatitis C Virus infection.

Thyroid disorders in chronic hepatitis C virus infection

The prevalence of thyroid disorders has been evaluated in patients with hepatitis C virus (HCV) infection by many studies. From a review of the published controlled studies, it is possible to observe that: (1) most investigated patients with chronic HCV hepatitis, while a minority evaluated hepatitis C virus antibody (HCVAb)- seropositive patients (the two conditions are not comparable with regards to thyroidal repercussions, in fact, HCVAb-seropositive patients do not necessarily display changes of the immune system present in chronically infected HCV patients); and (2) some authors selected as internal control hepatitis B virus (HBV)-infected patients, while others selected apparently healthy controls or HCVAb-negative subjects. Pooling all data about HCV-positive patients (with chronic hepatitis or HCVAb positivity) and using as control the sum of healthy controls, HBV-infected patients and sera negative for HCVAb, a significant increase of the prevalence has been observed both for thyroid autoimmune disorders (odds ratio [OR] = 1.6; 95% confidence interval = [C]) 1.4-1.9) as well as for hypothyroidism (OR = 2.9; 95% CI = 2.0-4.1). The results of the epidemiologic studies showing an association between HCV infection and thyroid cancer need to be confirmed. The abovementioned evidences seem sufficient to suggest careful thyroid monitoring during the follow-up of patients with HCV infection.

Rapid progression from subclinical to symptomatic overt hypothyroidism

OBJECTIVE

To report a case of Hashimoto's thyroiditis with rapid progression from subclinical to overt symptomatic hypothyroidism and to discuss the potential precipitating factors and the implications on clinical decisions about monitoring and treatment of early thyroid failure.

METHODS

We describe a patient with long-standing subclinical hypothyroidism who had progression to severe overt hypothyroidism during a 2-month period, without an identifiable precipitating factor. All medical care was provided at a single institution, and all relevant medical records were reviewed.

RESULTS

For at least 2 years, an 84-year-old man had a pattern of subclinical hypothyroidism, including normal levels of serum free thyroxine, serum thyrotropin concentrations ranging from 4.4 to 9.6 microIU/mL, and elevated levels of anti-thyroid peroxidase antibodies. During a 2-month period, symptoms of cold intolerance, a 4.5-kg weight gain, and fatigue developed, and the patient was found to have low free thyroxine and free triiodothyronine concentrations and a serum thyrotropin concentration of 80.9 microIU/mL. The patient did not use any medication previously identified as a trigger to the development of hypothyroidism, had no exposure to iodine or contrast administration, and reported no intercurrent infection that might explain the rapid progression of hypothyroidism.

CONCLUSION

Most patients with subclinical hypothyroidism have progression to overt hypothyroidism at a slow rate. Elderly patients with high antithyroid antibody titers may have a higher than previously recognized risk of rapid development of overt hypothyroidism, and earlier intervention with levothyroxine treatment may be indicated.

Is steroid therapy needed in the treatment of destructive thyrotoxicosis induced by alpha-interferon in chronic hepatitis C?

OBJECTIVE

Treatment with interferon (IFN) of patients affected by chronic hepatitis C (CH-C) may produce alterations in thyroid function, such as hypothyroidism, Graves'-like hyperthyroidism and destructive thyrotoxicosis (DT). IFN-induced DT is characterized by suppressed serum TSH levels, normal or elevated FT4 and FT3 concentrations, with the presence or absence of thyroid peroxidase antibodies and antithyroglobulin antibodies, the absence of thyroid receptor antibodies and radioactive iodine uptake suppressed or <5%.

DESIGN

IFN-induced DT is a mild clinical disease, because thyroid-destructive processes last for a short time and involve a small portion of the gland. At present, the therapeutic approach in DT suggests IFN withdrawal and 1-2 months of methylprednisolone treatment.

METHODS

In consideration of possible untoward side effects of steroid treatment in patients with CH-C, we studied two groups of patients with CH-C who developed DT after treatments with various preparations of recombinant IFN (with or without ribavirin). Patients sequentially entered the study during a 4-year period, at the time of DT diagnosis, when IFN therapy was discontinued. The first 12 subjects (group A) were treated with 8-16 mg/day methylprednisolone for 30-40 days after IFN withdrawal; in the following 15 patients (group B), IFN withdrawal was not followed by any additional treatment. All patients underwent clinical and laboratory controls of thyroid function at 1, 2, 3 and 6 months after DT diagnosis.

RESULTS

The results showed restoration of euthyroidism in both group A and group B patients at 6 months after DT diagnosis, regardless of steroid treatment.

CONCLUSIONS

The simple withdrawal of IFN therapy in patients with CH-C, who had developed DT, appears to be effective in the treatment of the thyroid disease. This therapeutic approach should be preferred in order to avoid possible undesired side effects of steroid therapy in patients with CH-C.

Interferon induced Autoimmune Thyroid Disease (AITD): a model for human autoimmunity

Interferon (IFN) alpha treatment for various conditions has been associated with thyroid autoimmunity. The incidence of interferon induced thyroid autoimmunity has been reported to range from 2.5% to 42%, possibly depending upon dose and duration of medical therapy and patient characteristics. It is not known whether IFN-alpha initiates autoimmune thyroid disease (AITD) or simply exacerbates AITD in individuals with subclinical AITD.

Thyroid involvement in patients with overt HCV-related mixed cryoglobulinaemia

BACKGROUND

Mixed cryoglobulinaemia (MC), a systemic vasculitis associated with hepatitis C virus (HCV) infection in >90% of cases, is frequently complicated by multiple organ involvement. The prevalence of thyroid disorders in MC has not yet been studied.

AIM

To investigate the prevalence and clinical features of thyroid involvement in patients with HCV-associated MC (HCV + MC).

DESIGN

Case-control study.

METHODS

HCV + MC patients (n = 93, 17 men and 76 women, mean +/- SD age 63 +/- 10 years, mean disease duration 14 +/- 7 years) consecutively referred to the Rheumatology Unit were matched by sex and age (+/- 2 years) to (i) 93 patients with chronic C hepatitis (CH) without MC and (ii) 93 healthy (HCV-negative) controls from the local population. Measurements included prevalence of hypo- or hyperthyroidism, thyroid autoantibodies, thyroid nodules and thyroid cancer.

RESULTS

By McNemar's chi(2) test, the following thyroid abnormalities were significantly more frequent in HCV + MC patients than in HCV-negative controls: serum anti-thyroperoxidase autoantibody (AbTPO) (28% vs. 9%, p = 0.001); serum AbTPO and/or anti-thyroglobulin autoantibody (31% vs. 12%, p = 0.004); subclinical hypothyroidism (11% vs. 2%, p = 0.038); thyroid autoimmunity (35% vs. 16%, p = 0.006). Serum AbTPO were also significantly more frequent in HCV + MC patients than in CH controls (28% vs. 14%, p = 0.035).

DISCUSSION

The prevalence of thyroid disorders is increased in patients with HCV-related mixed cryoglobulinaemia. We suggest careful monitoring of thyroid function in these patients.

Thyroid disorders in chronic hepatitis C

PURPOSE

To explore the association of hepatitis C virus (HCV) infection with thyroid disorders.

METHODS

We investigated the prevalence of thyroid disorders in 630 consecutive patients with chronic hepatitis due to HCV infection; all patients were free of cirrhosis and hepatocarcinoma, and were not on interferon treatment. Also included were a control group of 389 subjects from an iodine-deficient area, another control group of 268 persons living in an area of iodine sufficiency, and 86 patients >40 years of age with chronic hepatitis B. Levels of thyroid-stimulating hormone (TSH), free thyroxine (T(4)), and triiodothyronine (T(3)), as well as anti-thyroglobulin and anti-thyroid peroxidase antibodies, were measured.

RESULTS

Mean TSH levels were higher (P = 0.001), and free T(3) and free T(4) levels were lower (P <0.0001), in patients with chronic hepatitis C than in all other groups. Patients with chronic hepatitis C were more likely to have hypothyroidism (13% [n = 82]), anti-thyroglobulin antibodies (17% [n = 108]), and anti-thyroid peroxidase antibodies (21% [n = 132]) than were any of the other groups.

CONCLUSION

Both hypothyroidism and thyroid autoimmunity are more common in patients with chronic hepatitis C-even in the absence of cirrhosis, hepatocellular carcinoma, or interferon treatment-than in normal controls or those with chronic hepatitis B infection.

Iodine excess and hyperthyroidism

150 microg iodine are daily required for thyroid hormone synthesis. The thyroid gland has intrinsic mechanisms that maintain normal thyroid function even in the presence of iodine excess. Large quantities of iodide are present in drugs, antiseptics, contrast media and food preservatives. Iodine induced hyperthyroidism is frequently observed in patients affected by euthyroid iodine deficient goiter when suddenly exposed to excess iodine. Possibly the presence of autonomous thyroid function permits the synthesis and release of excess quantities of thyroid hormones. The presence of thyroid autoimmunity in patients residing in iodine-insufficient areas who develop iodine-induced hyperthyroidism has not been unanimously observed. In iodine-sufficient areas, iodine-induced hyperthyroidism has been reported in euthyroid patients with previous thyroid diseases. Euthyroid patients previously treated with antithyroid drugs for Graves' disease are prone to develop iodine-induced hyperthyroidism. As well, excess iodine in hyperthyroid Graves' disease patients may reduce the effectiveness of the antithyroid drugs. Occasionally iodine-induced hyperthyroidism has been observed in euthyroid patients with a previous episode of post-partum thyroiditis, amiodarone destructive or type II thyrotoxicosis and recombinant interferon-alpha induced destructive thyrotoxicosis. Amiodarone administration may induce thyrotoxicosis. Two mechanisms are responsible for this condition. One is related to excess iodine released from the drug, approximately 9 mg of iodine following a daily dose of 300 mg amiodarone. This condition is an iodine-induced thyrotoxicosis or type I amiodarone-induced thyrotoxicosis. The other mechanism is due to the amiodarone molecule that induces a destruction of the thyroid follicles with a release of preformed hormones. This condition is called amiodarone-induced destructive thyrotoxicosis or type II thyrotoxicosis. Patients developing type I thyrotoxicosis in general have preexisting nodular goiter whereas those developing type II thyrotoxicosis have a normal thyroid gland. The latter group of patients, after recovering from the destructive process, may develop permanent hypothyroidism as the consequence of fibrosis of the gland.

Iodine-Induced hypothyroidism

Iodine is an essential element for thyroid hormone synthesis. The thyroid gland has the capacity and holds the machinery to handle the iodine efficiently when the availability of iodine becomes scarce, as well as when iodine is available in excessive quantities. The latter situation is handled by the thyroid by acutely inhibiting the organification of iodine, the so-called acute Wolff-Chaikoff effect, by a mechanism not well understood 52 years after the original description. It is proposed that iodopeptide(s) are formed that temporarily inhibit thyroid peroxidase (TPO) mRNA and protein synthesis and, therefore, thyroglobulin iodinations. The Wolff-Chaikoff effect is an effective means of rejecting the large quantities of iodide and therefore preventing the thyroid from synthesizing large quantities of thyroid hormones. The acute Wolff-Chaikoff effect lasts for few a days and then, through the so-called "escape" phenomenon, the organification of intrathyroidal iodide resumes and the normal synthesis of thyroxine (T4) and triiodothyronine (T3) returns. This is achieved by decreasing the intrathyroidal inorganic iodine concentration by down regulation of the sodium iodine symporter (NIS) and therefore permits the TPO-H202 system to resume normal activity. However, in a few apparently normal individuals, in newborns and fetuses, in some patients with chronic systemic diseases, euthyroid patients with autoimmune thyroiditis, and Graves' disease patients previously treated with radioimmunoassay (RAI), surgery or antithyroid drugs, the escape from the inhibitory effect of large doses of iodides is not achieved and clinical or subclinical hypothyroidism ensues. Iodide-induced hypothyroidism has also been observed in patients with a history of postpartum thyroiditis, in euthyroid patients after a previous episode of subacute thyroiditis, and in patients treated with recombinant interferon-alpha who developed transient thyroid dysfunction during interferon-a treatment. The hypothyroidism is transient and thyroid function returns to normal in 2 to 3 weeks after iodide withdrawal, but transient T4 replacement therapy may be required in some patients. The patients who develop transient iodine-induced hypothyroidism must be followed long term thereafter because many will develop permanent primary hypothyroidism.

Autoimmune thyroid dysfunction induced by interferon-alpha treatment for chronic hepatitis C: screening and monitoring recommendations

OBJECTIVE

To analyze the proposed mechanisms of action of recombinant interferon-alpha (IFN-a) in causing autoimmune thyroid dysfunction, to identify pretreatment risk factors, and to provide recommendations for screening and monitoring of thyroid dysfunction during IFN-a therapy for chronic hepatitis C.

METHODS

Selected publications were reviewed to analyze the proposed mechanisms of autoimmune thyroid disorders. In addition, we examined the interrelationship of the thyroid and the liver, the occurrence of thyroid dysfunction in patients with chronic hepatitis C before and after IFN-a therapy, and the presence or absence of antithyroid antibodies in association with thyroid disease. Case reports were selected to demonstrate various IFN-a-induced thyroid dysfunction.

RESULTS

IFN-a induces thyroid dysfunction in 3 to 14% of all treated patients with chronic hepatitis C, leading to hypothyroidism, hyperthyroidism, or thyroiditis. In a few patients, thyroid disease will develop in the absence of antithyroid antibodies, a scenario that suggests a nonimmune-mediated mechanism. More frequently, patients develop antithyroid antibodies, which may progress to overt thyroid dysfunction. Through its immunomodulatory properties, IFN-a seems to act through major histocompatibility complex class I antigens to produce antithyroid antibodies and thyroid disease.

CONCLUSION

In patients receiving IFN-a therapy for chronic hepatitis C infection, identifiable risk factors for developing autoimmune thyroid dysfunction are preexisting overt thyroid or autoimmune disease, subclinical thyroid or autoimmune thyroid disease, and female gender. Pretreatment screening is recommended for all patients in whom IFN-a therapy is being considered, and periodic monitoring should be performed during such therapy. Thyroid disease need not be a contraindication to IFN-a therapy; early detection of subclinical or overt thyroid disease may allow uninterrupted continuation of IFN-a treatment.

Potassium iodide in dermatology: a 19th century drug for the 21st century-uses, pharmacology, adverse effects, and contraindications

Potassium iodide (KI) is a useful drug in the dermatologic armamentarium. It is successfully used for inflammatory dermatoses, most notably erythema nodosum, subacute nodular migratory panniculitis, nodular vasculitis, erythema multiforme, and Sweet's syndrome. KI is also successfully used for cutaneous and lymphocutaneous sporotrichosis. The precise mechanism by which KI acts is unknown. Although many minor side effects are common with this drug, major side effects can occur in pregnant patients and those with a history of kidney or thyroid disease. This article reviews the pharmacology, mechanism of action, indications, contraindications, and adverse effects of KI as a therapeutic agent.

Endocrine and neurological adverse effects of the therapeutic interferons

There is experimental evidence that the nervous central and the neuroendocrine systems can influence the immune system, which can in turn influence the brain activity. Endogenous cytokines are known to play a critical role in the pathophysiology of many diseases. The recently acquired experience on the adverse effects of therapeutic cytokines, particularly neurological and endocrine adverse effects, are further illustrative of these interferences. Interferons-alpha have been used in thousands of patients, so that the information accumulated with this group of closely related products is essential to delineate the potential and severity for non-immunological, but largely immune-mediated adverse effects to develop in patients treated with immuno-activating agents.

Recombinant interferon alpha (rIFN-alpha) does not potentiate the effect of iodine excess on the development of thyroid abnormalities in patients with HCV chronic active hepatitis

OBJECTIVE

To determine whether the administration of pharmacological quantities of iodine during interferon-alpha (rIFN-alpha) treatment of chronic viral hepatitis B and C (HCV) would exacerbate the potential adverse effects of rIFN alpha on thyroid function.

DESIGN

Thyroid function tests were carried out in 48 euthyroid patients before and during rIFN-alpha therapy of HCV. Twenty-one of these patients were also treated with 10 drops saturated solution of potassium iodine (SSKI, approximately 350 mg iodine daily). Eight patients with HCV but not treated with rIFN-alpha received 10 drops SSKI.

PATIENTS

All patients were enthyroid prior to rIFN-alpha therapy for HCV or iodine and thyroid function tests were similar in the three groups.

MEASUREMENTS

Serum free T4, free T3, and TSH concentrations were measured prior to and at 30 and 60 days of rIFN-alpha therapy in the three groups of patients. The serum TSH response to TRH was assessed before rIFN-alpha therapy and on day 60. Thyroid peroxidase antibodies were measured before and during therapy.

RESULTS

During the 2-month study period, similar small but significant decreases in serum FT4 and FT3 and compensatory small significant increases in TSH concentrations were observed in the patients treated with rIFN-alpha + iodine and iodine alone but not in the patients receiving rIFN-alpha alone. Abnormal thyroid function tests were observed more frequently in patients receiving rIFN-alpha + iodine and iodine alone compared to those receiving rIFN-alpha alone.

CONCLUSIONS

Excess iodine administered to patients treated with rIFN-alpha induced small changes in thyroid function similar to those observed in patients treated with iodine alone. Thus, rIFN-alpha and iodine do not appear to be synergistic in the development of abnormal thyroid function tests over a 2-month treatment period.