Patients treated with amiodarone may manifest altered thyroid hormone profile without thyroid dysfunction, or they may present with clinically significant. The effects of amiodarone on thyroid function tests in 100 patients treated for 6 weeks to 8 years are reported. In peripheral tissues, particularly the liver, amiodarone inhibits type i 5. May 27, 2004 amiodarone is an iodinerich drug used to treat cardiac dysrhythmias.
The team at medmastery are providing litfl readers with a series of foamed courses from across their website in this video from the thyroid disease masterclass,we look at how amiodarone affects thyroid function, when this effect stabilizes, and how often you should monitor the lab results of patients using amiodarone. Amiodarone can have many effects on thyroid function test results, even in the absence of hyperthyroidism or hypothyroidism. Amiodarone was synthesized in 1961 by tondeur and binon in the labaz laboratories in belgium. Pdf amiodaroneinduced thyroid dysfunction occurs in 1520% of amiodarone treated patients. Amiodarone may be continued in patients with amiodarone. Amiodarone blocks the action of thyroid hormone by the inhibition of 5. Effects of amiodarone therapy on thyroid function nature. Characteristic structural features of the drug are its high iodine content and its resemblance to thyroxine. Amiodarone can lead to both hypothyroidism and less commonly hyperthyroidism. In most cases, the treatment of amiodaroneinduced thyrotoxicosis ait requires stopping the amiodarone in addition to other. Men are at increased risk of amiodarone associated thyrotoxicosis in the uk. Patterns of amiodaroneinduced thyroid dysfunction in infants. Since the drug inhibits peripheral conversion of t 4 to t 3, many patients taking amiodarone have abnormal thyroid function studies increased t 4 and rt 3.
Amiodarone can cross the placenta, and the iodine released from amiodarone can affect thyroid function in the developing baby, as described in transient fetal hypothyroidism due to direct fetal administration of amiodarone for drug resistant fetal tachycardia. To clarify the pathophysiologic features and treatment of amiodarone. Although amiodarone is regarded as a highly effective antiarrhythmic agent, its use may lead to alterations in thyroid gland function andor thyroid hormone metabolism, partly because of its rich iodine content. Elimination from the body occurs with a halflife of approximately 100 days 3. D activity, which removes an atom of iodine from the outer ring of t 4 to generate t 3 and from the outer ring of rt 3 to produce 3,3. In someclinically hypothyroid amiodarone treated patients, free thyroxine index values may be normal. Amiodarone is an iodinebased, potent antiarrhythmic drug bearing a structural resemblance to thyroxine t4. The various effects of amiodarone on thyroid function thyroid. Although amiodarone is regarded as a highly effective antiarrhythmic agent, its use may lead to alterations in thyroid gland function and or thyroid hormone metabolism, partly because of its rich iodine content. In this study we aimed to describe the patterns of amiodaroneinduced thyroid dysfunction in our. Treatment with amiodarone is associated with changes in thyroid function tests, but also with thyroid dysfunction. The synthetic pathways of thyroxine t 4 and triiodothyronine t 3, along with the sites of action of antithyroid drugs, are summarised in fig 2. Medline abstract for reference 14 of amiodarone and. An antiarrhythmic drug, amiodarone, contains 37% iodine by weight and is structurally similar to the thyroid hormones.
It is a benzofuran derivative related to the obsolete vasodilator khellin. Amiodarone and its metabolites may have a direct cytotoxic effect on the thyroid follicular cells, which causes a destructive thyroiditis. However, amiodarone is associated with a number of side effects, including thyroid dysfunction both hypo and hyperthyroidism, which is due to amiodarones high iodine content and its direct toxic effect on the thyroid. Amiodarone has many unique side effects one of which is it can affect thyroid function.
Amiodaroneinduced hypothyroidism aih does not pose. The structure of amiodarone resembles that of thyroxine, and treatment with amiodarone may alter thyroid function. It was requested that a tsh be checked to monitor for this unique side effect of amiodarone. Another condition that can develop as a complication of amiodarone is thyrotoxicosis. If you also take drugs for hepatitis c, talk with your doctor. Thyroid hormones and thyroid function tests duration. These adverse effects may occur in patients with or without preexisting thyroid disease. In each 200mg tablet, there is 75mg of iodine 37% of the amiodarone mass of which approxi mately 10% of the iodine is released as free iodide daily. I receive funding for clinical research from medtronic. Amiodarone is a potent antiarrhythmic agent that is used to treat ventricular arrhyth mias and atrial fibrillation. Understanding the subtle patterns of pediatric amiodarone inducedthyroid dysfunction may guide clinical practice and development of more rigorous pediatricspeci. Proportion of type 1 and type 2 amiodarone induced. Dronedarone is a relatively new antiarrhythmic drug which was designed to. Men are at increased risk of amiodaroneassociated thyrotoxicosis in the uk.
Amiodarone is an iodinerich drug used to treat cardiac dysrhythmias. Jabrockahybel a, bednarczuk t, bartalena l, pach d, ruchala m, et al. Amiodarone is an iodinecontaining compound with some structural similarity to thyroxine. Amiodaroneinduced hyperthyroidism is more common in iodinedeficient regions of the world, whereas amiodaroneinduced hypothyroidism is usually seen in. Because of the high iodine content of amiodarone, the thyroid gland is effectively saturated, thus preventing further uptake of isotopes of iodine.
Amiodarone is a benzofuran compound figure 1 that contains approximately 37% iodine by weight and bears a remarkable structural resemblance to thyroid hormones figure 1ac rao et al. Although amiodaroneinduced hypothyroidism poses no particular problem, amiodaroneinduced thyrotoxicosis ait is a diagnostic and therapeutic challenge. Unfortunately, when amiodarone is given to a euthyroid normal thyroid function patient, the normal physiologic process for the formation of the thyroid hormones, thyroxine t4 and 3,5,3triiodothyronine t3, can be adversely affected. The problem with amiodarone is that it contains a relatively large concentration of iodine. Amiodarone is a benzofuranicderivative iodinerich drug widely used for the treatment of tachyarrhythmias and, to a lesser extent, of ischemic heart disease. The drug prevents the recurrence of lifethreatening ven. Additionally, the chemical structure of amiodarone is similar to the structure of t4, or thyroxine, which is one of the hormones produced by the thyroid gland. Amiodarone cordarone is a commonly prescribed medication for the management of both atrial and ventricular arrhythmias. In fact, approximately 37% of this drug consists of iodine.
However amiodarone and its main metabolically active metabolite desethylamiodarone can adversely affect many organs, including the thyroid gland. Tsh labwork was done and elevated at about 30 indicating hypothyroidism normal range is approximately 0. Patients treated with amiodarone may manifest altered thyroid hormone profile without thyroid dysfunction, or they may present with clinically significant amiodarone induced. The mechanism for amiodaroneinduced hyperthyroidism and. Amico ja, richardson v, alpert b, klein i 1984 clinical and chemical assessment of thyroid function during therapy with amiodarone. Amiodarone toxicity can therefore occur well after drug withdrawal 4.
Amiodarone is a lipid soluble benzofuranic antiarrhythmic drug that has complex effects on the thyroid and may interfere significantly with thyroid hormone metabolism. The various effects of amiodarone on thyroid function. It has the potential to cause thyroid dysfunction because of this iodinerich chemical structure. Being that your heart doctor started the thyroid medication, i would say they are probably already on top of taking the best care of you they can. Ait is primarily related to excess iodine induced thyroid hormone synthesis in an abnormal thyroid gland.
Amiodarone is very lipophilic and is concentrated in adipose tissue, cardiac and skeletal muscle, and the thyroid. In patients with this particular condition, the thyroid gland would produce an excess number of thyroid hormones. Patterns of amiodaroneinduced thyroid dysfunction in. Consideration must be given to the benefit of amiodarone on lifethreatening arrhythmias, the fact it has such a long half life and hence no immediate benefit on thyroid status if stopped and the fact that amiodarone reduces t4 to t3 conversion so an initial exacerbation of thyroid symptoms may occur on its cessation leger et al. Manage hypothyroidism by reducing the dose of or discontinuing cordarone and thyroid hormone supplementation.
In someclinically hypothyroid amiodaronetreated patients, free thyroxine index values may be normal. Nov 24, 2009 amiodarone is widely used for treating cardiac arrhythmias, but is associated with various adverse effects. Amiodarone could also be discontinued if approved by the heart specialist. Radioiodine ablation of the thyroid to allow the reintroduction of amiodarone treatment in patients with a prior history of amiodaroneinduced thyrotoxicosis. Pituitarythyroid function tests during amiodarone therapy. It may cause an increase in serum levels of thyroxine, reverse triiodothyronine, and thyroidstimulating hormone and a decrease in serum triiodothyronine levels. Thats because antiarrhythmic medications often come with a. Amiodarone is a potent antiarrhythmic agent that is used to treat ventricular arrhythmias and atrial fibrillation. The drug prevents the recurrence of lifethreatening ventricular arrhythmias and produces a modest reduction of sudden deaths in highrisk patients. Oct 08, 2018 amiodarone and its metabolites may have a direct cytotoxic effect on the thyroid follicular cells, which causes a destructive thyroiditis.
The publication provides great explanations and rationales on how to approach amiodarone induced thyrotoxicosis. One patient became thyrotoxic and 10 developed latent or overt hypothyroidism. Amiodarone bears a remarkable structural resemblance to thyroid hormones. Highlights of prescribing information these highlights do. Singh bn, nademanee k amiodarone and thyroid function. In most cases, the treatment of amiodarone induced thyrotoxicosis ait requires stopping the amiodarone in addition to other. Amiodarone and the thyroid american journal of medicine. Among the drugs affecting the thyroid gland, no drug has puzzled, and at the same time fascinated, endocrinologists more than amiodarone. Ocular toxicity and blue man syndrome are also discussed. Pathology outlines amiodarone induced hyperthyroidism. Amiodarone is an antiarrhythmic medication used to treat and prevent a number of types of irregular heartbeats. The effects of amiodarone on thyroid function depend on underlying thyroid status and dietary iodine intake.
Results subclinical hypothyroidism, thyroid stimulating hormone tsh level 4. Capitals indicate lifethreatening, underlines indicate most frequent. Amiodarone is widely used for treating cardiac arrhythmias, but is associated with various adverse effects. Siralthough amiodarone is viewed as a highly effective antiarrythmic agent, its use may lead to alterations in thyroid gland function, thyroid hormone metabolism, or both more than rarely. Amiodarone and the thyroid the american journal of medicine. However, amiodarone is associated with a number of side effects, including thyroid dysfunction both hypo and hyperthyroidism, which is due to amiodarone s high iodine content and its direct toxic effect on the thyroid. This includes ventricular tachycardia vt, ventricular fibrillation vf, and wide complex tachycardia, as well as atrial fibrillation and paroxysmal supraventricular tachycardia. Amiodarone and thyroid function litfl medmastery podcast. Amiodarone is a benzofuranic derivative whose structural formula closely resembles that of human thyroid hormone t4.
It may cause an increase in serum levels of thyroxine, reverse triiodothyronine, and thyroid stimulating hormone and a decrease in serum triiodothyronine levels. Amiodarone is a benzofuranic, iodinerich antiarrhyth mic drug class iii that causes thyroid dysfunction in 15 to 20% of patients 1. In 1418% of amiodarone treated patients, there is overt thyroid dysfunction, either amiodarone induced thyrotoxicosis ait or amiodarone induced hypothyroidism aih. In summary, serum t4 levels rise by 2040% during the first month of therapy and then. Amiodarone is a benzofuran compound figure 1 that contains approximately 37% iodine by weight and bears a remarkable structural resemblance to thyroid hormones figure 1a c rao et al. Amiodarone is an antiarrhythmic medication for atrial and ventricular tachyarrhythmias, and less commonly for ischemic heart disease and congestive heart failure. Amiodarone thyroid toxicity 2015 bryan heart conference shannon wakeley md 9515 disclosures i speak on behalf of the following companies. It can also lead to hyperthyroidism through a destructive effect on thyroid cells, a form of thyroiditis called ait type 2. Summaries for patients from clinical thyroidology march 2012 table of contents pdf file for saving and printing. Amiodarone therapy is associated with a number of side effects, including thyroid dysfunction thyrotoxicosis in 215% and hypothyroidism in 520% of patients, respectively. Mar 09, 2014 amiodarone has many unique side effects one of which is it can affect thyroid function. Amiodarone is a benzofuran derivative containing two atoms of iodine per molecule figure 1. Amiodarone induced thyrotoxicosis ait is a clinically.
Effects of amiodarone on thyroid function annals of. Both ait and aih may develop either in apparently normal thyroid glands or in glands with preexisting, clinically silent abnormalities. If you have a defibrillator or pacemaker, talk with your doctor. If diarrhea or throwing up happens, talk with the doctor.
Thyroid uptake measurements i123 or i1, which are used to differentiate causes of hyperthyroidism, are generally unreliable in patients who have been taking amiodarone. Amiodarone, a benzofuranic iodinerich antiarrhythmic drug, causes thyroid dysfunction in 1520% of cases. Amiodarone, a benzofuranicderivative iodinerich drug used mostly for tachyarrhythmias, often causes changes in the peripheral metabolism of thyroid hormones mainly due to the inhibition of 5deiodinase activity. It often causes changes in thyroid function tests typically an increase in serum t4 and rt3, and a decrease in serum t3, concentrations. Serial thyroid function tests were performed over 14. Between 8% and 17% of the amiodarone iodine is freed to inorganic iodine resulting in the release of 3 mg of inorganic iodine per 100 mg amiodarone each day. The drugs high iodine content likely is a factor in its effects on the thyroid gland. This condition refers to an excessive number of thyroid hormones accumulating in tissues throughout the body. Management of amiodaronerelated thyroid problems ncbi. Therefore, a patient taking a standard 200 mg daily dose of amiodarone ingests 75 mg of organic iodine each day. The free base contains 39% iodine by weight fig 1, and chronic treatment is associated with 40fold increases in plasma and urinary iodide levels.
Amiodarone and the thyroid dysfunction thyroid research. Amiodarone and its metabolite desethylamiodarone can act as a competitive antagonist of t3 at the cardiac cellular level. To clarify the pathophysiologic features and treatment of amiodarone associated hypothyroidism and thyrotoxicosis. The expected effects of amiodarone treatment on individual biochemical parameters of thyroid function are outlined below and summarised in. Amiodaroneinduced thyroid dysfunction in clinical practice. The effects of amiodarone on thyroid function depend on. It is known to produce thyroid abnormalities ranging from abnormal thyroid function testing to overt hypothyroidism or hyperthyroidism. Amiodarone a class iii antiarrhythmic drug, with multiple effects on myocardial depolarization and repolarization that make. Amiodarone crosses the placenta and reaches measurable levels in breast milk. In 2016, american thyroid association published guidelines on diagnosis and management of hyperthyroidism, including the amiodarone scenario. Jul 29, 2018 the problem with amiodarone is that it contains a relatively large concentration of iodine. Data sources englishlanguage articles identified through a medline search for 1975 to 1995, using the terms.
681 380 686 572 365 1353 1026 1182 390 1137 730 1554 1409 1462 89 1478 1515 449 811 1422 229 1022 262 232 1005 609 1343 106 696 356