Safety of long-term antithyroid drug treatment? A systematic review

Systemic Factors Affecting Pain Management in Dentistry

There are several factors that affect a patient's experience of pain. These include both local and systemic factors. The systemic factors that affect patients' dental and orofacial pain experience include, but not limited to, hormonal, nutritional, systemic infections, neurodegenerative, and autoimmune, among others. Comprehensive medical history is essential to delineate any possible systemic factors affecting pain experience. A thorough review of systems should form the foundation, since multiple factors can affect the prognosis of pain management. This would facilitate early recognition and trigger prompt referrals to the appropriate medical professionals. This helps to reduce the health care burden.

Approach to the Patient Considering Long-term Antithyroid Drug Therapy for Graves' Disease

Antithyroid drugs (ATD) are the treatment of choice for the majority of patients with Graves' hyperthyroidism worldwide. However, relapse of hyperthyroidism after withdrawal of arbitrarily chosen conventional 12 to 18 months of therapy is very common. In the last 2 decades, many studies have shown that treatment with long-term ATD (LT-ATD) is effective and safe in the maintenance of euthyroidism. In addition, it has been reported that serum TSH receptor antibody may not decrease permanently before 5 to 6 years of ATD treatment, and clinical trials have shown that ≥5 years of ATD treatment is accompanied by remission in the majority of patients with Graves' hyperthyroidism. The objective of this article is to discuss the optimal time to withdraw of conventional ATD therapy, to illustrate the decision-making of the management of recurrent hyperthyroidism, to review the proper management of LT-ATD, and to generate suggestions for lifelong ATD treatment by discussing 4 scenarios of decision-making in patients with Graves' disease.

Methimazole-induced urticaria in hyperthyroid patients: A safe re-administration protocol

PURPOSE

The safety profile of methimazole (MMI) seems to be better than propylthiouracil in the management of hyperthyroidism. It is therefore advisable to use IMM as the first choice in Graves' patients. It is important to keep this drug in patients regardless of minor side effects. We report a case series of MMI-induced urticaria and provide a stepwise protocol for the safe re-administration of MMI.

METHODS

It was a retrospective case series including all patients having manifested urticaria following MMI intake for hyperthyroidism; notified to the Pharmacovigilance Unit of the Clinical Pharmacology Department (March 2013-January 2022).

RESULTS

We have included 11 patients (SR: 0.22). The median time interval between the start of MMI and the onset of urticaria averaged 14.5 days. The median daily dose of MMI was 40mg. MMI was interrupted in all patients. Urticaria has progressively resolved after drug interruption and antihistamine intake. Reintroduction of MMI was performed in 10/11 patients as follows: one quarter of the daily dose on the first day, half of the daily dose on the 4th day, the three quarters of the daily dose on the 7th day, to reach the scheduled total dose on the 10th day. Cetirizine was added at the time of reintroduction and withdrawn 2 weeks later. All the patients were successfully controlled.

CONCLUSION

Given the importance of this drug in the management of hyperthyroidism, MMI should not be withdrawn in cases of urticaria. After the resolution of urticaria, a gradual reintroduction of MMI should be attempted with concomitant antihistamine therapy.

Statins and thyroid eye disease (TED): a systematic review

PURPOSE

Thyroid eye disease (TED) is the foremost extrathyroidal manifestation of Graves' disease (GD). Currently, available treatments do not entirely prevent the long-term consequences of TED and have distinct disadvantages. Therefore, this systematic review explored available evidence regarding the efficacy of statins in preventing and treating TED.

METHODS

Relevant studies investigating statin usage in patients with GD or TED were identified by searching Medline (Pubmed and Ovid), Scopus, Web of Science, ProQuest, and Cochrane Library databases (from the database inception to September 2023). The review was done according to the PRISMA statement. Web searching was done independently by two investigators. Two researchers independently extracted the data, and any disagreement was adjudicated by consensus. Based on the study design, the studies' quality appraisal was done using the Newcastle-Ottawa Scale (NOS) and Version 2 of the Cochrane risk-of-bias tool (RoB2).

RESULTS

The literature search identified 145 publications, of which four met the inclusion criteria (Three retrospective cohort studies and one randomized clinical trial) and were reviewed in full text. The two retrospective cohort studies demonstrated the beneficial effects of statins on TED in newly diagnosed GD Stein et al. showed that statins, regardless of the type, prevent or delay TED (HR: 0.74 (0.65-0.84)), especially in men or treatment duration of more than one year. Nilsson et al. fascinatingly revealed that at least 60 days of statin usage in the preceding year could decrease the risk of TED development by around 40%. One RCT showed a higher treatment response for active moderate-to-severe TED in patients with hypercholesterolemia who took atorvastatin 20 mg in addition to ivGC for 24 weeks without any increase in serious side effects. The retrospective study revealed that the need for reconstructive surgery was reduced in patients with severe TED who received statin therapy.

CONCLUSION

Statin therapy could be a potential adjunctive modality for preventing and treating TED.

TRIAL REGISTRATION

PROSPERO registration number: CRD42022315522.

MACE and Hyperthyroidism Treated With Medication, Radioactive Iodine, or Thyroidectomy

Importance

Excessive thyroid hormones from hyperthyroidism increase cardiovascular risks. Among 3 available treatments for hyperthyroidism, comparisons of long-term outcomes associated with antithyroid drugs (ATDs), radioactive iodine (RAI), and surgery to treat newly diagnosed hyperthyroidism are lacking.

Objective

To compare risks of major adverse cardiovascular events (MACE) and all-cause mortality among patients with hyperthyroidism treated with ATDs, RAI, or surgery.

Design, Setting, and Participants

This nationwide cohort study used the Taiwan National Health Insurance Research Database. Patients aged 20 years or older with newly diagnosed hyperthyroidism between 2011 and 2020 were enrolled. Treatment groups were determined within 18 months from diagnosis, with follow-up until the development of MACE, death, or the end date of the database, whichever came first. Data were analyzed from October 2022 through December 2023.

Exposures

The ATD group received ATDs only. RAI and surgery groups could receive ATDs before treatment. Anyone who underwent thyroid surgery without RAI was classified into the surgery group and vice versa.

Main Outcomes and Measures

The primary outcomes included MACE (a composite outcome of acute myocardial infarction, stroke, heart failure, and cardiovascular mortality) and all-cause mortality.

Results

Among 114 062 patients with newly diagnosed hyperthyroidism (mean [SD] age, 44.1 [13.6] years; 83 505 female [73.2%]), 107 052 patients (93.9%) received ATDs alone, 1238 patients (1.1%) received RAI, and 5772 patients (5.1%) underwent surgery during a mean (SD) follow-up of 4.4 (2.5) years. Patients undergoing surgery had a significantly lower risk of MACE (hazard ratio [HR] = 0.76; 95% CI, 0.59-0.98; P = .04), all-cause mortality (HR = 0.53; 95% CI, 0.41-0.68; P < .001), heart failure (HR = 0.33; 95% CI, 0.18-0.59; P < .001), and cardiovascular mortality (HR = 0.45; 95% CI, 0.26-0.79; P = .005) compared with patients receiving ATDs. Compared with ATDs, RAI was associated with lower MACE risk (HR = 0.45; 95% CI, 0.22-0.93; P = .03). Risks for acute myocardial infarction and stroke did not significantly differ between treatment groups.

Conclusions and Relevance

In this study, surgery was associated with lower long-term risks of MACE and all-cause mortality, while RAI was associated with a lower MACE risk compared with ATDs.

Clinical manifestations and early effectiveness of methimazole in patients with graves' hyperthyroidism-related severe hepatic dysfunction

BACKGROUND

Graves' hyperthyroidism (GH) is often accompanied by mild to moderate liver injury, but severe hepatic dysfunction (SHD) is relatively rare. Whether patients with GH-related SHD can be treated with methimazole (MMI) remains controversial. This study aimed to determine the clinical characteristics and to evaluate the role of low-dose MMI for such patients.

METHODS

33 patients with GH-related SHD were selected for this retrospective study in the Fifth Medical Center of Chinese PLA General Hospital from January 2017 to July 2022. The clinical manifestations, therapeutic responses, and effectiveness of MMI were evaluated.

RESULTS

Systemic jaundice (100.0%), yellow urine (100.0%), fatigue (87.9%), and goiter (66.7%) were the main symptoms. Total bilirubin (TBIL) had no linear correlation with free triiodothyronine (FT3) (r = -0.023, p = .899), free thyroxine (FT4) (r = 0.111, p = .540), T3 (r = -0.144, p = .425), and T4 (r = 0.037, p = .837). On the 14th day after admission, FT3, FT4, T3, T4, TBIL, direct bilirubin (DBIL), alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), γ-glutamyltransferase (GGT), and international normalized ratio (INR) decreased compared with the baseline (p < .05). The decrease rates of FT3, FT4, T3, T4, TBIL, and DBIL in the MMI group were higher than those in the non-MMI group (p < .05). The improvement rate of the MMI group (77.8%) was higher than that of the non-MMI group (9.5%, p = .001). MMI treatment is an independent predictor affecting the early improvement of patients (OR = 0.022, p = .010).

CONCLUSIONS

The main clinical manifestations of patients with GH-related SHD were symptoms related to liver disease. Low-dose MMI was safe and effective for them.

A disproportionality analysis of the adverse effect profiles of methimazole and propylthiouracil in patients with hyperthyroidism using the Japanese Adverse Drug Event Report Database

BACKGROUND

Antithyroid drugs (ATDs) are frequently used to achieve euthyroidism in patients with hyperthyroidism. ATDs cause characteristic common and rare adverse events; however, comprehensive comparisons between methimazole (MMI) and propylthiouracil (PTU) in terms of adverse events are limited.

METHODS

In this study, we thoroughly explored adverse events in association with MMI and PTU use with a disproportionality analysis using the Japanese Adverse Drug Event Report (JADER) database and evaluated the prevalence of MMI and PTU prescriptions using the National Database of Health Insurance Claims and Specific Health Checkups (NDB) Open Data Japan. We analyzed 3271 cases of MMI use and 1029 cases of PTU use with respect to 9789 preferred terms (PTs) for adverse events registered in the JADER database by calculating and comparing reporting odds ratios (RORs).

RESULTS

We found that 8 PTs, including agranulocytosis (p < 0.0001, 4.01-fold), aplasia cutis congenita (p < 0.0001, 123.22-fold), and exomphalos (p = 0.0002, 22.17-fold), demonstrated significantly higher RORs (more than 4-fold) for MMI use than for PTU use. Nineteen PTs, including anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (p < 0.0001, 29.84), rapidly progressive glomerulonephritis (p < 0.0001, 6.44), and pulmonary alveolar hemorrhage (p < 0.0001, 7.77), had RORs for PTU use more than four times those for MMI use. NDB Open Data Japan showed more frequent PTU prescriptions than MMI prescriptions for women of reproductive age.

CONCLUSIONS

This large-scale study confirmed that a variety of congenital malformations were identified as having significantly high RORs for MMI use, while diseases related to ANCA-associated vasculitis were specific to PTU.

Hyperthyroidism: aetiology, pathogenesis, diagnosis, management, complications, and prognosis

Hyperthyroidism is a common condition with a global prevalence of 0·2-1·3%. When clinical suspicion of hyperthyroidism arises, it should be confirmed by biochemical tests (eg, low TSH, high free thyroxine [FT4], or high free tri-iodothyonine [FT3]). If hyperthyroidism is confirmed by biochemical tests, a nosological diagnosis should be done to find out which disease is causing the hyperthyroidism. Helpful tools are TSH-receptor antibodies, thyroid peroxidase antibodies, thyroid ultrasonography, and scintigraphy. Hyperthyroidism is mostly caused by Graves' hyperthyroidism (70%) or toxic nodular goitre (16%). Hyperthyroidism can also be caused by subacute granulomatous thyroiditis (3%) and drugs (9%) such as amiodarone, tyrosine kinase inhibitors, and immune checkpoint inhibitors. Disease-specific recommendations are given. Currently, Graves' hyperthyroidism is preferably treated with antithyroid drugs. However, recurrence of hyperthyroidism after a 12-18 month course of antithyroid drugs occurs in approximately 50% of patients. Being younger than 40 years, having FT4 concentrations that are 40 pmol/L or higher, having TSH-binding inhibitory immunoglobulins that are higher than 6 U/L, and having a goitre size that is equivalent to or larger than WHO grade 2 before the start of treatment with antithyroid drugs increase risk of recurrence. Long-term treatment with antithyroid drugs (ie, 5-10 years of treatment) is feasible and associated with fewer recurrences (15%) than short-term treatment (ie, 12-18 months of treatment). Toxic nodular goitre is mostly treated with radioiodine (131I) or thyroidectomy and is rarely treated with radiofrequency ablation. Destructive thyrotoxicosis is usually mild and transient, requiring steroids only in severe cases. Specific attention is given to patients with hyperthyroidism who are pregnant, have COVID-19, or have other complications (eg, atrial fibrillation, thyrotoxic periodic paralysis, and thyroid storm). Hyperthyroidism is associated with increased mortality. Prognosis might be improved by rapid and sustained control of hyperthyroidism. Innovative new treatments are expected for Graves' disease, by targeting B cells or TSH receptors.

Long-term thionamide antithyroid treatment of Graves' disease

Thionamide antithyroid drugs (ATD) are the treatment of choice for Graves' hyperthyroidism. The major drawback of ATD treatment for 1-2 years is the relapse of hyperthyroidism in about 50% of patients. Recently, it has been shown that ATD treatment for more than five years is accompanied by long-term remission in majority of patients without additional major side effects in both adults and children. Compared to radioactive iodine therapy, long-term ATD results in more favorable outcomes. This review summarizes the evidence on long-term ATD therapy regarding the remission rate of hyperthyroidism, efficacy and safety, indications and mode of therapy in patients with hyperthyroidism.

Approach to the Patient With a Suppressed TSH

Subclinical hyperthyroidism (SCH) is a laboratory diagnosis defined by a serum thyrotropin (TSH) concentration below the reference range (< 0.4 mU/L in most assays), and a free thyroxine (FT4) and 3,5,3'-triiodothyronine levels (FT3) in the reference range. Many patients diagnosed with SCH will be clinically euthyroid while others may present with manifestations characteristic of thyroid hormone excess, such as tachycardia, tremor, intolerance to heat, bone density loss, or weight loss. In addition to the laboratory abnormalities, patient factors such as age, symptoms, and underlying heart and bone disease are used to stratify patients for the risk of adverse outcomes and determine the appropriate treatment. Evaluation should include repeat thyroid function tests to document persistent TSH suppression, investigation of the underlying cause, as well as evaluation of the patient's risk of adverse outcomes in the setting of a subnormal TSH. Persistent SCH has been associated with an increased risk of a range of adverse events, including cardiovascular events such as atrial fibrillation and heart failure, bone loss and fracture, and in some studies, cognitive decline. Despite the consistent association of these adverse events with SCH, prospective studies showing improved outcomes with treatment remain limited. Management options include observation without active therapy, radioactive iodine ablation of the thyroid, antithyroid medication, thyroid surgery, or radiofrequency ablation, as appropriate for the patient and clinical setting. The choice of therapy should be guided by the underlying etiology of disease, patient factors, and the risks and benefits of each treatment option.

Therapeutic plasma exchange in hyperthyroidism prior to surgery

PURPOSE

Therapeutic plasma exchange (TPE) is a treatment option to reduce thyroid hormones in the event of contraindication or unresponsiveness to antithyroid drugs (ATDs).

METHODS

We analyzed 11 patients with hyperthyroidism who received TPE prior to surgery between January 2008 and December 2016 at our center.

RESULTS

In total, 41 processes were applied to 11 patients with hyperthyroidism. The median age was 40 years, and 90.9% of the patients were female. Seven patients had Graves' disease, while four had a toxic multinodular goiter. The distribution of TPE indications comprised contraindication to ATDs (64%) and insufficient response to ATDs (36%). An adequate response was not obtained with TPE in two patients, and cholestyramine plus methimazole and Lugol solution were applied. The median number of TPE sessions was 3. During the TPE period, a β-blocker was applied concurrently except in one patient who was contraindicated for the drug. The reduction in FT3 and FT4 hormones and the increase in TSH levels were statistically significant after TPE application (p values of 0.003, 0.033 and 0.008, respectively). Regarding adverse events of TPE application, an allergic reaction was seen in one patient, while prolongation of prothrombin time without any clinical findings was seen in another patient. Ten patients underwent total thyroidectomy, and one patient underwent a gynecological surgery procedure without any major complications.

CONCLUSION

The American Society for Apheresis guideline, which is the most referenced guideline, mentions the utilization of TPE before thyroid surgery, only in patients with thyrotoxicosis despite the wider necessity of this treatment choice under the condition of uncontrolled hyperthyroidism prior to any kind of surgery. We concluded that TPE is a reliable and effective application in patients with hyperthyroidism before any surgical procedure, according to our study results.

2021 Asia-Pacific Graves' Disease Consortium Survey of Clinical Practice Patterns in the Management of Graves' Disease

AIM

Although Graves' disease (GD) is common in endocrine practices worldwide, global differences in diagnosis and management remain. We sought to assess the current practices for GD in countries across Asia and the Pacific (APAC), and to compare these with previously published surveys from North America and Europe.

METHODS

A web-based survey on GD management was conducted on practicing clinicians. Responses from 542 clinicians were received and subsequently analysed and compared to outcomes from similar surveys from other regions.

RESULTS

A total of 542 respondents participated in the survey, 515 (95%) of whom completed all sections. Of these, 86% were medical specialists, 11% surgeons, and 3% nuclear medicine physicians. In addition to serum thyroid-stimulating hormone (TSH) and free thyroxine assays, most respondents would request TSH-receptor autoantibody (TRAb) measurement (68%) during initial work-up. Thyroid ultrasound is requested by about half of respondents (53%), while the use of nuclear medicine scans is limited. The preferred first-line treatment is anti-thyroid drug (ATD) therapy (79%) with methimazole (MMI) or carbimazole (CBZ), followed by radioiodine (RAI; 19%) and surgery (2%). In case of surgery, one-third of respondents would opt for a subtotal rather than a total thyroidectomy. In case of mild Graves orbitopathy (GO), ATDs (67%) remains the preferred treatment, but a larger proportion of clinicians prefer surgery (20%). For a patient with intention to conceive, the preferred treatment pattern remained unchanged, although propylthiouracil (PTU) became the preferred ATD-agent during the first trimester. In comparison to European and American practices, marked differences were noted in the relatively infrequent usage of nuclear medicine scans and the overall higher use of a ATDs and β-blockers and adjunctive ATD-treatment during RAI in the APAC-group.

CONCLUSION

Although regional differences regarding the diagnosis and management of GD are apparent in this first pan-Asia-Pacific survey, this study reveals the overall approach to the management of this disease in Asia-Pacific generally tends to fall between the trends appreciated in the American and European cohorts.

Approach to the Patient: Management and the Long-term Consequences of Graves' Disease in Children

In children, Graves' disease (GD) is the most common cause of hyperthyroidism. Most pediatric patients with GD will not go into lasting remission, even following many years of antidrug therapy. Thus, most pediatric patients will require radioactive iodine (RAI) or surgery. When antithyroid drugs are used, methimazole is the drug of choice. When methimazole is used in children, up to 20% will have minor adverse reactions and serious adverse events occur in up to 1%. RAI is an effective form of therapy when the thyroid size is less than 80 g. Because of concerns of whole-body radiation exposure, it is recommended that RAI be avoided in children under 5 years of age, and dosages less than 10 mCi be used between 5 and 10 years of age. Surgery is an effective treatment in children if performed by a high-volume thyroid surgeon. Because of the scarcity of high-volume pediatric thyroid surgeons, a multidisciplinary approach using pediatric surgeons and endocrine surgeons can be considered. Whereas there is a trend toward long-term antithyroid drug therapy in adults, for several reasons, this approach may not be practical for children. Determining the optimal treatment for the pediatric patient with GD, requires consideration of the risks and benefits relating to age and likelihood of remission.

Appropriate duration of antithyroid drug treatment as a predictor for relapse of Graves' disease: a systematic scoping review

BACKGROUND

Following the conventional 12-18 month antithyroid drug (ATD) treatment in Graves' disease (GD), 50% of patients experience relapse of hyperthyroidism.

OBJECTIVE

The aim of this systematic scoping review was critical appraisal of duration of ATD therapy in the last 80 years.

METHODS

Articles were identified through the search of PubMed from January 1, 1941 to April 30, 2021. All study types were included. Articles were eligible if they reported data on the length of ATD treatment, particularly thyroid hormones and TSH receptor antibodies (TRAb) concentrations and specifically those with data on the remission and/or relapse rates.

RESULTS

We described major progress regarding the duration of ATD therapy and related outcomes at every 20 years. Articles of 1941-1960 were mainly concerned with determination of favorable treatment, minimal effective dose, side effects and rate of remission after < 12-month ATD therapy. Studies with larger number of patients and longer follow-ups appeared in 1961-1980; higher remission rate after 18-24 months versus 6 months of ATD therapy was reported. Articles of 1981-2000 focused on identification of factors associated with high relapse rates after discontinuation of ATD. In 2001-2021, ATD became the first choice of treatment in many countries. However, 12-18 months of ATD therapy was arbitrarily chosen as the appropriate option. According to recent studies, persistent normalization of TRAb occurs after 5 years of methimazole therapy and ATD treatment of > 60 months could offer a 4-year remission rate of 85%.

CONCLUSION

Long-term ATD treatment for more than 60 months is safe and effective, has the highest remission rate and cures most patients with GD; hence, it should be considered as the most appropriate duration for ATD therapy in these patients.

Long-term methimazole therapy in Graves' hyperthyroidism and adverse reactions: a Danish multicenter study

Purpose

In this prospective multicenter study with patients newly diagnosed with Graves' hyperthyroidism (GH), we studied the timing and characteristics of adverse drug reactions in patients treated with anti-thyroid drugs (ATD) for up to 48 months.

Methods

Patients with GH were treated with ATD until remission and hereafter with a low-dose regime to keep the patients in remission. The patients were followed with blood samples and recording of adverse events approximately every second month for the first 2 years and every third month for the following 2 years.

Results

We included 208 patients and the patients were treated for a median of 22 (range: 0.5-49) months. Ten percent of the patients experienced adverse drug reactions and 75% of the cases occurred during the first 6 months. After 24 months, the methimazole dose was lowered to 5 mg/day, and after this time point, no further adverse drug reactions were recorded. Skin reactions were the most prominent reaction, comprising 68% of the registered reactions, and no hepatic and bonemarrow affection was recorded.

Conclusion

With this study, we report the frequency, timing of occurrence, and characteristics of adverse drug reactions when treating GH with the ATD drug methimazole for up to 48 months. Long-term low-dose methimazole treatment can be a cost-effective and straightforward treatment option if adverse drug reactions such as severe hepatic and bone marrow affection are kept in mind.

Management of Graves' hyperthyroidism: present and future

INTRODUCTION

Graves' disease (GD) is an autoimmune disorder due to loss of tolerance to the thyrotropin receptor (TSHR) and ultimately caused by stimulatory TSHR antibodies (TSHR-Ab). GD may be associated with extrathyroidal manifestations, mainly Graves' orbitopathy. Treatment of GD relies on antithyroid drugs (ATDs), radioactive iodine (RAI), thyroidectomy. The major ATD limitation is the high recurrence rate after treatment. The major drawback of RAI and thyroidectomy is the inevitable development of permanent hypothyroidism.

AREAS COVERED

Original articles, clinical trials, systematic reviews, meta-analyses from 1980 to 2021 were searched using the following terms: Graves' disease, management of Graves' disease, antithyroid drugs, radioactive iodine, thyroidectomy, Graves' orbitopathy, thyroid-eye disease.

EXPERT OPINION

ATDs are the first-line treatment worldwide, are overall safe and usually given for 18-24 months, long-term treatment may decrease relapses. RAI is safe, although associated with a low risk of GO progression, particularly in smokers. Thyroidectomy requires skilled and high-volume surgeons. Patients play a central role in the choice of treatment within a shared decision-making process. Results from targeted therapies acting on different steps of the autoimmune process, including iscalimab, ATX-GD-59, rituximab, blocking TSHR-Ab, small molecules acting as antagonists of the TSHR, are preliminary or preclinical, but promising in medium-to-long perspective.

Benefits of Long-Term Continuation of Low-Dose Methimazole Therapy in the Prevention of Recurrent Hyperthyroidism in Graves' Hyperthyroid Patients: A Randomized Prospective Controlled Study

BACKGROUND

The long-term continuation of the low-dose antithyroid drug (ATD) beyond the standard duration of ATD therapy of 12-18 months to prevent recurrent hyperthyroidism (RH) is recommended with low quality of evidence.

OBJECTIVES

To examine whether long-term continuation of low-dose ATD beyond the recommended duration of treatment would provide a benefit in the prevention of RH in patients with Graves' hyperthyroidism (GH) who achieved euthyroid status with a standard course of ATD therapy.

METHODS

A 36-month prospective randomized controlled study was conducted in 184 patients who had first diagnosed GH and were treated with a standard regimen of ATD therapy using methimazole (MMI) until achieving euthyroidism that was stably maintained for at least 6 months with a low-dose of (2.5-5 mg/day) MMI. All patients had neither a history of adverse effects from MMI, recurrent GH, severe and active ophthalmopathy nor conditions known to affect thyroid function before randomization. The patients were randomized into 2 groups: one group (92 cases) was assigned to discontinue (DISCONT-MMI) and the other (92 cases) was assigned to continue low-dose MMI (CONT-MMI) that was taken at the time of enrollment. The patients in both groups were followed up at 3, 6, 12, 18, 24, 30, and 36 months. The rate of RH was compared between both groups, and the adverse effects and risk factors of RH were also studied.

RESULTS

At the end of the 36-month study, 83 cases in CONT-MMI and 90 cases in DISCONT-MMI were eligible for analysis. The cumulative rates of RH in CONT-MMI were significantly lower than those in DISCONT-MMI at every follow-up time point (1.2% vs. 11.2%, 6.8% vs. 18.4%, 11.0% vs. 27.2%, 11.0% vs. 35.0%, and 11.0% vs. 41.2% at 6, 12, 18, 24, and 36 months, respectively; p < 0.01). Cox proportional hazard multivariate analysis showed that there were 2 factors independently associated with the risk of RH, including continuation of low-dose MMI therapy, which decreased the risk of RH by 3.8 times (HR = 0.26, p = 0.007, 95% CI = 0.10-0.70) and age onset of hyperthyroidism before 40 years, which increased the risk of RH by 2.9 times (HR = 2.9, p = 0.015, 95% CI = 1.23-6.88). Neither minor nor major adverse effects of low-dose MMI therapy were observed during the study period.

CONCLUSIONS

In Graves' hyperthyroid patients with no or nonsevere ophthalmopathy who have completed a standard course of methimazole therapy without an adverse effect and have achieved an euthyroid status that is stably maintained with low-dose methimazole, a long-term continuation of the low-dose methimazole of 2.5-5 mg daily is effective and safe in the prevention of recurrent hyperthyroidism or maintenance of euthyroid status as long as the low-dose methimazole is continued. (TCTR20170705002).

The longer the antithyroid drug is used, the lower the relapse rate in Graves' disease: a retrospective multicenter cohort study in Korea

PURPOSE

Current literature suggests 12-18 months of antithyroid drug (ATD) treatment for patients with Graves' disease, but the risk of relapse is high. Although some studies reported better outcomes of long-term ATD treatment, recent data that suggest the optimal treatment duration are limited.

METHODS

We performed a multicenter retrospective cohort study of 908 patients newly diagnosed with Graves' disease between 2006 and 2013. The relapse rate according to ATD treatment duration was analyzed.

RESULTS

After initial ATD treatment, 338 patients (37.2%) had relapsed. The relapse rate according to ATD treatment duration was 42.4% at 1 year, 38.5% at 2 years, 33.8% at 3 years, 31.7% at 4 years, 30.2% at 5 years, 27.8% at 6 years, and 19.1% at more than 6 years, respectively, demonstrating a significant decreasing trend (p = 0.003). In a multivariable Cox regression analysis, ATD treatment duration was an independent risk factor for relapse (p = 0.043).

CONCLUSIONS

The longer that ATD therapy is used, the lower the relapse rate is in patients with Graves' disease. Long-term ATD treatment may be considered in Graves' patients who do not show complications or an economic burden from hyperthyroidism.

Long-term antithyroid drug therapy

PURPOSE OF REVIEW

Over the last 1-2 decades, patients and physicians have preferred antithyroid drug therapy as the initial treatment of Graves' disease, rather than radioactive iodine or surgery. More recently, the concept of long-term antithyroid drug therapy (LTADT; >24 months of treatment) has also become increasingly popular.

RECENT FINDINGS

Data from cohort studies and a prospective randomized trial suggest that LTATD therapy is safe and is associated with a higher chance of remission from Graves' disease than is shorter-term therapy. Also, LTADT may be associated with better quality of life and other clinical outcomes compared to radioiodine and surgery.

SUMMARY

Long-term antithyroid drug therapy is appropriate for children and young adults. This approach is a reasonable option in those who are doing well on a stable low dose of antithyroid drug therapy, and especially those who wish to avoid definitive treatment with radioactive iodine or surgery, given their inherent risks and need for lifelong hormonal replacement therapy.

Rash and cholestatic liver injury caused by methimazole in a woman with Turner syndrome and Graves's disease: a case report and literature review

BACKGROUND

Rash and cholestatic liver injury caused by methimazole (MMI) in patients with Turner syndrome (TS) and Graves's disease (GD) are rarely reported, and there is a paucity of reports on the management of this condition. It is not clear whether propylthiouracil (PTU) can be used as a safe alternative in this case.

CASE PRESENTATION

A 37-year-old woman was admitted to our hospital with rash, severe pruritus and a change in urine colour after 2 months of GD treatment with MMI. Physical examination showed rash scattered over the limbs and torso, mild jaundice of the sclera and skin, short stature, facial moles, immature external genitals and diffuse thyroid gland enlargement. Liver function tests indicated an increase in total bilirubin, direct bilirubin, total bile acid, glutamic pyruvic transaminase, glutamic oxaloacetic transaminase and alkaline phosphatase. The level of sex hormones suggested female hypergonadotropic hypogonadism. The karyotype of peripheral blood was 46, X, i(X)(q10)/45, X. After excluding biliary obstruction and other common causes of liver injury, combined with rash and abnormal liver function following oral administration of MMI, the patient was diagnosed as having TS with GD and rash and cholestatic liver injury caused by MMI. MMI was immediately discontinued, and eleven days after treatment with antihistamine and hepatoprotective agents was initiated, the rash subsided, and liver function returned to nearly normal. Because the patient did not consent to administration of ¹³¹I or thyroid surgery, hyperthyroidism was successfully controlled with PTU. No adverse drug reactions were observed after switching to PTU.

CONCLUSIONS

While patients with TS and GD are undergoing treatment with MMI, their clinical manifestations, liver functions, and other routine blood test results should be closely monitored. When patients with TS and GD manifest adverse reactions to MMI such as rash and cholestatic liver injury, it is necessary to discontinue MMI and treat with antihistamine and hepatoprotective agents. After the rash subsides and liver function returns to nearly normal, PTU can effectively control hyperthyroidism without adverse drug reactions.

Comparison of long-term antithyroid drugs versus radioactive iodine or surgery for Graves' disease: A review of the literature

BACKGROUND

The management of Graves' disease (GD) in the US is shifting towards increased use of anti-thyroid drugs (ATD). If patients fail to achieve remission after a standard course of therapy of 12-18 months, long-term treatment with ATD (≥24 months) may be chosen over definitive therapy with radioiodine (RAI) or surgery. Clinicians will need to contrast this strategy to ablative therapies as they help patients in decision making.

SUMMARY

Review of the literature illustrates that long-term ATD delivers euthyroidism with minimal complications, low financial cost and with an advantageous profile regarding quality of life (QoL) and other biological outcomes.

CONCLUSIONS

Long-term ATD is a viable alternative to ablative therapies in the management of GD offering advantages across multiple patient centred outcomes. Decision making must factor differences in this approach compared to ablative therapies and ultimately be tailored to individualized patient situations.

Efficacy of low-dose methimazole in control of multiple relapses of Graves' hyperthyroidism: a case report

INTRODUCTION

Methimazole (MMI) is the treatment of choice for patients with Graves' disease. The major drawback of this treatment is the relapse of hyperthyroidism in half of the patients after discontinuation of the recommended conventional 12-18 months of MMI treatment. TSH receptor antibody (TRAb) concentration is recognized as the strongest predictor of hyperthyroidism relapse. In this case report, efficacy of low-dose MMI to control hyperthyroidism even after multiple recurrences in the setting of normal TRAb concentrations is shown.

CASE PRESENTATION

An 80-year-old Iranian woman with Graves' disease was treated with MMI for 31 years. While receiving treatment, she always had a normal serum TRAb concentration; however, three times during the 31 years she decided to stop MMI therapy, and each time the disease recurred 16-21 months after MMI withdrawal. It is noteworthy that she maintained euthyroidism with the low-dose 1.25-2.5 mg MMI daily without any adverse events during three decades of treatment.

CONCLUSIONS

Normal serum TRAb is not a sufficiently strong marker to predict relapse of Graves' hyperthyroidism. Long-term therapy with low-dose MMI is an effective and safe treatment to sustain euthyroidism.

Treatment of Subclinical Hyperthyroidism in the Elderly: Comparison of Radioiodine and Long-Term Methimazole Treatment

Background: This study aimed to compare the effectiveness and safety of radioiodine (RAI) and long-term methimazole (MMI) in the treatment of subclinical hyperthyroidism (SH) in the elderly. Methods: From 306 patients, aged ≥65 years, with SH, 83 patients with thyrotropin <0.1 mU/L entered the study. In this randomized parallel-group trial, 41 and 42 patients were randomized to either RAI or long-term MMI treatment, respectively. Results: In the RAI and MMI groups, 3 and 4 patients were excluded due to side effects, choosing other modes of treatment, and not returning for follow-up; 35 and 36 patients completed 60 months of follow-up, respectively. In the RAI group, 23 (66%) became hypothyroid, and 12 (34%) remained euthyroid 60 months after a fixed dose of 15 mCi RAI. In the MMI group, the starting dose was 10 mg daily and decreased to 4.9 ± 1.0, 4.3 ± 1.0, 4.4 ± 1.4, 4.3 ± 1.8, and 3.7 ± 1.3 mg after 1, 2, 3, 4, and 5 years of continuous MMI treatment, employing titration method. By the end of study, 34 (94%) patients were euthyroid and 2 patients with diffuse goiter developed spontaneous hypothyroidism with MMI treatment. Minor adverse events occurred in both groups in the first four months of treatment. No death or serious side effects were observed during 60 months of follow-up. Conclusions: Both RAI and long-term low-dose MMI therapies are effective and safe for treatment of SH in the elderly.

Preoperative plasmapheresis in patients with Graves' disease intolerant to antithyroid drugs

Antithyroid drugs (ATDs) are the mainstay of treatment for Graves' disease with possible detrimental adverse effects. Surgery or radioactive iodine (RAI) ablation is the second choice among the treatment options in cases of non-remission. Normalization of serum thyroid hormone levels as much as possible is required before surgery or RAI to prevent thyrotoxic crisis in patients with uncontrolled Graves' disease. In recent decades, therapeutic plasma exchange (TPE) has been used in the treatment of thyroid storm, drug-induced hepatotoxicity and agranulocytosis, or patients with hyperthyroidism scheduled for emergency surgery. TPE is an effective method to reduce serum FT3, FT4, and TRAB levels in severe hyperthyroid conditions. Although TPE-related complications are rare, the risk of bleeding needs to be taken into consideration in patients who were scheduled for surgery within 24 h after TPE. In terms of reducing intraoperative bleeding, patients can be referred to surgery 24-48 h after TPE, or fresh frozen plasma transfusion can be the preferred treatment for emergency cases.

Antithyroid drugs in Graves' hyperthyroidism: differences between "block and replace" and "titration" regimes in frequency of euthyroidism and Graves' orbitopathy during treatment

PURPOSE

Whereas antithyroid drugs (ATD) are the preferred treatment modality for Graves' hyperthyroidism (GH), there is still controversy about the optimal regimen for delivering ATD. To evaluate whether 'Block and Replace' (B + R) and 'Titration' (T) regimes are equivalent in terms of frequency of euthyroidism and Graves' Orbitopathy (GO) during ATD therapy.

METHODS

A prospective multicentre observational cohort study of 344 patients with GH but no GO at baseline. Patients were treated with ATD for 18 months according to B + R or T regimen in line with their institution's policy.

RESULTS

Baseline characteristics were similar in both groups. In the treatment period between 6 and 18 months thyrotropin (TSH) slightly increased in both groups, but TSH was on average 0.59 mU/L (95% CI 0.27-0.85) lower in the B + R group at all time points (p = 0.026). Serum free thyroxine (FT4) remained stable during the same interval, with a tendency to higher values in the B + R group. The point-prevalence of euthyroidism (TSH and FT4 within their reference ranges) increased with longer duration of ATD in both groups; it was always higher in the T group than in the B + R group: 48 and 24%, respectively, at 6 months, 81 and 58% at 12 months, and 87 and 63% at 18 months (p < 0.002). There were no significant differences between the B + R and T regimens with respect to the fall in thyrotropin binding inhibiting immunoglobulins (TBII) or thyroid peroxidase antibodies (TPO-Ab). GO developed in 15.9% of all patients: 9.1 and 17.8% in B + R group and T group, respectively, (p = 0.096). GO was mild in 13% and moderate-to-severe in 2%.

CONCLUSION

The prevalence of biochemical euthyroidism during treatment with antithyroid drugs is higher during T compared to B + R regimen. De novo development of GO did not differ significantly between the two regimens, although it tended to be higher in the T group. Whether one regimen is clinically more advantageous than the other remains unclear.

Control of Graves' hyperthyroidism with very long-term methimazole treatment: a clinical trial

BACKGROUND

Long-term antithyroid drug therapy has become one of the options for treatment of Graves' hyperthyroidism. The aim of this study was to compare thyroid status in those who discontinued methimazole (MMI) treatment after 12.8 years with those who continued MMI as long as 24 years.

METHODS

Fifty nine patients with Graves' disease on long-term MMI for 14.2 ± 2.9 years were recruited; 32 patients (54%) decided to discontinue MMI and 27 (46%) preferred additional years of MMI treatment. All patients were followed for a mean of 6 additional years.

RESULTS

Of 27 patients who continued MMI up to 24 years, suppressed serum thyrotropin (TSH) was not observed in any patient after the seventh year of treatment. Serum free thyroxine, triiodothyronine, TSH and TSH receptor antibody concentrations remained normal up to the length of the study. Mean daily dose of MMI to maintain TSH in the reference range decreased gradually and reached to 2.8 ± 1.7 mg by 24 years of MMI treatment. No adverse reaction related to MMI occured during additional years of therapy. In 32 patients who discontinued MMI, hyperthyroidism relapsed in 6 patients (19%), one left follow-up and 25 (78%) remained euthyroid during the study.

CONCLUSIONS

Long-term low dose MMI treatment may be a lifelong effective and safe therapeutic modality in patients with Graves' hyperthyroidism for prevention of relapse, if studies from other centers confirm findings of this research.

TRIAL REGISTRATION

IRCT201009224794N1, 2010-10-25. Retrospectively registered. https://www.irct.ir/trial/5143 .

Long-Term Antithyroid Drug Treatment of Graves' Disease in Children and Adolescents: A 20-Year Single-Center Experience

BACKGROUND/PURPOSE

Graves' disease (GD) is the most common cause of thyrotoxicosis in children and adolescents. There is some debate regarding the optimal treatment and predicting factors of remission or relapse in children and adolescents with GD. In this study, we report a retrospective study of 195 children and adolescents with GD treated at a single tertiary institution in Korea.

METHODS

This study included children and adolescents with GD diagnosed before 19 years of age from January of 2000 to October of 2020. The diagnosis of GD was based on clinical features, high thyroxine (FT4), suppressed thyroid-stimulating hormone, and a positive titer of thyrotropin receptor antibodies. Remission was defined as maintenance of euthyroid status for more than six months after discontinuing antithyroid drug (ATD).

RESULTS

A total of 195 patients with GD were included in this study. The mean age at diagnosis was 12.9 ± 3.2 years, and 162 patients (83.1%) were female. Among all 195 patients, five underwent thyroidectomy and three underwent radioactive iodine therapy. The mean duration of follow-up and ATD treatment were 5.9 ± 3.8 years and 4.7 ± 3.4 years, respectively. The cumulative remission rates were 3.3%, 19.6%, 34.1%, 43.5%, and 50.6% within 1, 3, 5, 7, and 10 years of starting ATD, respectively. FT4 level at diagnosis (P = 0.001) was predicting factors for remission [HR, 0.717 (95% CI, 0.591 - 0.870), P = 0.001]. Methimazole (MMI)-related adverse events (AEs) occurred in 11.3% of patients, the most common of which were rash and hematologic abnormalities. Of a total of 26 AEs, 19 (73.1%) occurred within the first month of taking MMI.

CONCLUSIONS

In this study, the cumulative remission rate increased according to the ATD treatment duration. Long-term MMI treatment is a useful treatment option before definite treatment in children and adolescents with GD.

Methimazole Treatment and Risk of Acute Pancreatitis: A Population-based Cohort Study

CONTEXT

A warning has been recently issued by the European Medicine Agency (EMA) regarding a potential increased risk of acute pancreatitis (AP) in methimazole (MMI) users.

OBJECTIVE

To investigate the association between MMI and the diagnosis of AP in a population-based study.

MATERIALS AND METHODS

A retrospective analysis of administrative health databases was conducted (2013-2018). Relevant data were obtained from: (1) inhabitants registry, (2) hospital discharge records (ICD-9-CM 577.0), and (3) drug claims registry (ATC H03BB02). We evaluated AP risk in MMI users in 18 months of treatment, stratifying results by trimester. Poisson regression was used to estimate the age- and sex-adjusted rate ratios (RR), and the relative 95% confidence intervals (CI), comparing rates of AP between MMI users and nonusers. The absolute risk of AP in MMI users was also calculated.

RESULTS

A total of 23 087 new users of MMI were identified. Among them, 61 hospitalizations occurred during the study period. An increase in AP risk was evident during the first 3 trimesters of therapy (RR 3.40 [95% CI: 2.12-5.48]; RR 2.40 [95% CI: 1.36-4.23]; RR 2.80 [95% CI: 1.66-4.73]), but disappeared thereafter. The AP absolute risk in MMI users during the first 18 months of treatment was less than 0.4% in all sex and age classes.

CONCLUSIONS

Our results support the EMA warning, suggesting an increased risk of AP associated with MMI use. However, such an increase seems limited to the first months of MMI treatment. Moreover, in absolute terms, the probability of AP is low among patients, well below 1%.

Management of Graves Thyroidal and Extrathyroidal Disease: An Update

CONTEXT

Invited update on the management of systemic autoimmune Graves disease (GD) and associated Graves orbitopathy (GO).

EVIDENCE ACQUISITION

Guidelines, pertinent original articles, systemic reviews, and meta-analyses.

EVIDENCE SYNTHESIS

Thyrotropin receptor antibodies (TSH-R-Abs), foremost the stimulatory TSH-R-Abs, are a specific biomarker for GD. Their measurement assists in the differential diagnosis of hyperthyroidism and offers accurate and rapid diagnosis of GD. Thyroid ultrasound is a sensitive imaging tool for GD. Worldwide, thionamides are the favored treatment (12-18 months) of newly diagnosed GD, with methimazole (MMI) as the preferred drug. Patients with persistently high TSH-R-Abs and/or persistent hyperthyroidism at 18 months, or with a relapse after completing a course of MMI, can opt for a definitive therapy with radioactive iodine (RAI) or total thyroidectomy (TX). Continued long-term, low-dose MMI administration is a valuable and safe alternative. Patient choice, both at initial presentation of GD and at recurrence, should be emphasized. Propylthiouracil is preferred to MMI during the first trimester of pregnancy. TX is best performed by a high-volume thyroid surgeon. RAI should be avoided in GD patients with active GO, especially in smokers. Recently, a promising therapy with an anti-insulin-like growth factor-1 monoclonal antibody for patients with active/severe GO was approved by the Food and Drug Administration. COVID-19 infection is a risk factor for poorly controlled hyperthyroidism, which contributes to the infection-related mortality risk. If GO is not severe, systemic steroid treatment should be postponed during COVID-19 while local treatment and preventive measures are offered.

CONCLUSIONS

A clear trend towards serological diagnosis and medical treatment of GD has emerged.

Subclinical Thyroid Dysfunction and the Risk of Cardiovascular Disease

The prevalence of subclinical hypothyroidism (SH) is 3-10%. The prevalence of subclinical hyperthyroidism (SHr) is 0.7-9.7%. Thyroid hormones affect cardiac electrophysiology, contractility, and vasculature. SH is associated with an increased risk of coronary heart disease (CHD), especially in subjects under 65. SHr seems to be associated with a slightly increased risk of CHD and an increase in CHD-related mortality. Both SH and SHr carry an increased risk of developing heart failure (HF), especially in those under 65. Both SH and SHr are associated with worse prognoses in patients with existing HF. SH is probably not associated with atrial fibrillation (AF). SHr, low normal thyroid-stimulating hormone (TSH) and high normal free thyroxine (FT4) are all associated with the increased risk of AF. An association between endothelial dysfunction and SH seems to exist. Data regarding the influence of SHr on the peripheral vascular system are conflicting. SH is a risk factor for stroke in subjects under 65. SHr does not increase the risk of stroke. Both SH and SHr have an unfavourable effect on cardiovascular disease (CVD) and all-cause mortality. There is a U-shaped curve of mortality in relation to TSH concentrations. A major factor that modifies the relation between subclinical thyroid disease (SCTD) and mortality is age. SH increases blood pressure (BP). SHr has no significant effect on BP. Lipids are increased in patients with SH. In SHr, high-density lipoprotein cholesterol and lipoprotein( a) are increased. SCTD should be treated when TSH is over 10 mU/l or under 0.1 mU/l. Treatment indications are less clear when TSH is between normal limits and 0.1 or 10 mU/L. The current state of knowledge supports the understanding of SCTD's role as a risk factor for CVD development. Age is a significant confounding factor, probably due to age-associated changes in the TSH reference levels.

Long-Term Treatment of Hyperthyroidism with Antithyroid Drugs: 35 Years of Personal Clinical Experience

Background: None of the current therapeutic approaches for management of Graves' disease has been able to re-establish normal thyroid function in all patients. Objective: To describe the author's 35 years of personal experience in the management of Graves' hyperthyroidism and, in doing so, review current articles published on the long-term medical treatment of hyperthyroidism. Methods: All published articles related to ≥4 years of continuous antithyroid drug (ATD) treatment were searched. Findings were added and compared with studies published by the authors on the same topic. Results: Long-term ATD treatment is effective and safe, both in children and adults, for treatment of hyperthyroidism. Treatment of Graves' patients with ATDs >60 months causes euthyroidism up to 4 years after discontinuation of ATDs in the majority of patients. Long-term ATD therapy is not inferior to radioiodine therapy and may sometimes even be superior in some aspects, when considering serum lipid profile, cardiac function, mood, and cognition. Conclusions: Long-term ATD therapy for Graves' hyperthyroidism is efficient and safe and induces control of hyperthyroidism, without rendering the patient hypothyroid in the majority of patients.

A Clinical Debate: What Is the Therapeutic Choice for Recurrent Graves' Hyperthyroidism?

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Remission Rate of Graves' Disease and the Trend of Changes in Serum TSH Receptor Antibodies in Prolonged Antithyroid Drug Treatment

Context: Graves’ disease is an autoimmune disease caused by thyrotropin receptor antibodies (TRAb). These antibodies can be measured and used for the diagnosis, prediction of remission, and risk of Graves’ orbitopathy development. There are three treatments for Graves’ disease that have remained unchanged for the last 75 years: Antithyroid drugs, radioiodine, and surgery. Antithyroid drugs are the first treatment option worldwide and are usually used for 12 - 18 months. Recent reports suggest the use of antithyroid drugs for more than 18 months with better outcomes. This review focuses on two aspects of treatment with antithyroid drugs: The impact of using antithyroid drugs for more than 12 - 18 months on remission rates and the trend of TRAb during prolonged antithyroid drug treatment. Evidence Acquisition: A review was performed in Medline on the published work regarding the duration of ATD treatment and remission of Graves' disease and also ATD treatment and TRAb status during the 1990 - 2019 period. Results: Remission rates are variable (30% - 80%), and many clinical and genetic factors serve as predictors. The long-term use of antithyroid drugs appears to increase remission rates. TRAb values usually decline during ATD treatment, but the trend could occur in two ways: Becoming negative or showing a fluctuating pattern. However, approximately 10% of the patients will remain TRAb-positive after five years of treatment with antithyroid drugs. Conclusions: Antithyroid drugs can be used for long periods with an increase in remission rates, and a gradual decrease in TRAb levels, with the disappearance of TRAb in 90% of the patients after 60 months.

Antithyroid Drugs

The thionamide drugs, i.e. carbimazole and its metabolite methimazole (MMI), and propylthiouracil (PTU) have extensively been used in the management of various forms of hyperthyroidism over the past eight decades. This review aims to summarize different aspects of these outstanding medications. Thionamides have shown their own acceptable efficacy and even safety profiles in treatment of hyperthyroidism, especially GD in both children and adults and also during pregnancy and lactation. Of the antithyroid drugs (ATDs) available, MMI is the preferred choice in most situations taking into account its better efficacy and less adverse effects accompanied by once-daily dose prescription because of a long half-life and similar cost. Considering the more severe teratogenic effects of MMI, PTU would be the selected ATD for treatment of hyperthyroidism during pre-pregnancy months and the first 16 weeks of gestation. Recent studies have confirmed the efficacy and safety of long-term MMI therapy with low maintenance doses for GD and toxic multinodular goiter. Despite the long-term history of ATD use, there is still ongoing debate regarding their pharmacology and diverse mechanisms of action, viz. their immunomodulatory effects, and mechanisms and susceptibility factors to their adverse reactions.