Hyperthyroidism iodine
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Hyperthyroidism and Iodine: Understanding the Connection
Introduction to Hyperthyroidism and Iodine
Hyperthyroidism is a condition characterized by the overproduction of thyroid hormones, which can lead to a variety of health issues. Iodine, an essential element for thyroid hormone synthesis, plays a significant role in the development and management of hyperthyroidism. This article explores the relationship between iodine and hyperthyroidism, focusing on iodine-induced hyperthyroidism (IIH) and its epidemiology, mechanisms, and clinical implications.
Iodine-Induced Hyperthyroidism (IIH) and Radiographic Procedures
Iodine-induced hyperthyroidism (IIH) can occur following the administration of iodinated contrast media (ICM) during radiographic procedures. A systematic review and meta-analysis revealed that the incidence of overt hyperthyroidism after ICM exposure is extremely low, with an overall prevalence of 0.1%1. This suggests that while IIH is a potential risk, it is relatively rare in clinical practice.
Mechanisms of Iodine-Induced Hyperthyroidism
The thyroid gland has intrinsic mechanisms to maintain normal function even in the presence of excess iodine. However, in certain conditions, these mechanisms can fail, leading to hyperthyroidism. For instance, patients with euthyroid iodine-deficient goiter or those with preexisting thyroid conditions are more susceptible to IIH when exposed to excess iodine2. Additionally, drugs like amiodarone, which contain high levels of iodine, can induce hyperthyroidism through two mechanisms: iodine-induced thyrotoxicosis (type I) and amiodarone-induced destructive thyrotoxicosis (type II)2.
Epidemiology of Iodine-Induced Hyperthyroidism
IIH is most commonly observed in older individuals with long-standing nodular goiter and in regions with chronic iodine deficiency. It can also occur in younger individuals, particularly after an increase in iodine intake through prophylactic programs3. The introduction of iodized salt in iodine-deficient regions has been associated with a transient increase in the prevalence of hyperthyroidism, particularly in areas with poor monitoring of iodine intake8.
Iodine Fortification and Hyperthyroidism
Iodine fortification of salt, implemented to prevent goiter and nodular hyperthyroidism, has been shown to increase the incidence of hyperthyroidism, especially in young adults. A study in Denmark reported a significant rise in hyperthyroidism cases following iodine fortification, with the highest increase observed in individuals aged 20-39 years6. This suggests that even cautious iodization can lead to an increase in hyperthyroidism incidence, highlighting the need for careful monitoring.
Long-term Risks of Iodine-Induced Hyperthyroidism
IIH has been linked to long-term cardiovascular risks, including an increased incidence of atrial fibrillation and flutter. A retrospective cohort study found that patients with IIH had a higher risk of developing these conditions compared to those who remained euthyroid after iodine exposure10. This underscores the importance of monitoring and managing IIH to prevent long-term complications.
Conclusion
Iodine plays a crucial role in thyroid health, but its excess can lead to hyperthyroidism, particularly in susceptible individuals. While the incidence of IIH following radiographic procedures is low, the introduction of iodized salt in deficient regions can transiently increase hyperthyroidism cases. Understanding the mechanisms and epidemiology of IIH is essential for effective prevention and management, ensuring that the benefits of iodine supplementation are maximized while minimizing potential risks.
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Most relevant research papers on this topic
Incidence of Iodine-induced Hyperthyroidism after Administration of Iodinated Contrast during Radiographic Procedures: A Systematic Review and Meta-analysis of the Literature.
The incidence of iodine-induced hyperthyroidism after iodinated contrast media administration during radiographic procedures is extremely low.
Meta-Analysis
Rigorous JournalIodine excess and hyperthyroidism.
Iodine-induced hyperthyroidism can occur in euthyroid patients with previous thyroid diseases, and may be exacerbated by amiodarone administration.
Highly CitedIodine-induced hyperthyroidism: occurrence and epidemiology.
Iodine-induced hyperthyroidism (IIH) is a rare but potentially serious condition, particularly affecting elderly individuals with heart disease and those in areas with limited medical care.
Literature ReviewHighly CitedGlobal epidemiology of hyperthyroidism and hypothyroidism
Iodine nutrition, ageing, smoking, genetics, ethnicity, and endocrine disruptors influence thyroid disease epidemiology, with iodine supplementation playing a key role in prevention and treatment.
Highly CitedIodine deficiency and thyroid disorders.
Optimizing population iodine intake is crucial to reduce the prevalence of thyroid disorders and improve thyroid function.
Highly CitedIncrease in incidence of hyperthyroidism predominantly occurs in young people after iodine fortification of salt in Denmark.
Iodine fortification of salt in Denmark increased the incidence of hyperthyroidism, particularly in young adults, and may lead to a decrease in elderly cases of nodular hyperthyroidism.
Observational Study
Very Rigorous JournalHighly CitedIodine excess.
Iodine excess can cause chronic hypothyroidism and iodine-induced hyperthyroidism, potentially promoting thyroid autoimmunity.
Highly CitedRisks of iodine-induced hyperthyroidism after correction of iodine deficiency by iodized salt.
The risk of iodine-induced hyperthyroidism after correcting iodine deficiency is closely related to a recent excessive increment of iodine supply.
Observational StudyHighly CitedTHE COURSE OF HYPERTHYROIDISM UNDER IODINE MEDICATION
Iodine treatment in hyperthyroidism leads to a sequence of gradual recurrence, gradual return, and sudden exacerbation, with recurrence occurring frequently and postiodine reaction occurring frequently.
Iodine-Induced Hyperthyroidism and Long-term Risks of Incident Atrial Fibrillation and Flutter.
Iodine-induced hyperthyroidism is associated with an increased risk of atrial fibrillation/flutter, particularly among females.
Observational Study