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Related Concept Videos

Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers01:12

Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers

Class III antiarrhythmic drugs are a group of medications that can prolong action potentials in the heart. They achieve this by blocking potassium channels or enhancing inward currents from sodium channels. However, these drugs have a unique property of "reverse use-dependence," which is most pronounced at slower heart rates and can lead to torsades de pointes—a specific type of arrhythmia. However, it is essential to note that excessive QT interval prolongation—a measure of the heart's...
Hyperthyroidism II: Pathophysiology01:27

Hyperthyroidism II: Pathophysiology

Hyperthyroidism is a hypermetabolic state caused by elevated levels of thyroid hormones, triiodothyronine (T3) and thyroxine (T4). It results from dysregulation at the thyroid, pituitary, or immune system level and affects multiple organ systems.PathophysiologyThe most common cause of hyperthyroidism is Graves’ disease, an autoimmune disorder in which antibodies, specifically thyroid-stimulating antibodies (TSAb), a subtype of TSH receptor antibodies (TRAb), bind to and activate TSH receptors...
Hypothyroidism II: Pathophysiology01:23

Hypothyroidism II: Pathophysiology

Hypothyroidism is a disorder characterized by insufficient production of thyroid hormones, which regulate metabolism, energy balance, and multiple organ systems.TypesHypothyroidism is classified based on the level of dysfunction. Primary hypothyroidism results from intrinsic thyroid gland dysfunction, causing reduced hormone production despite normal or increased stimulation. Secondary hypothyroidism arises from inadequate thyroid-stimulating hormone (TSH) secretion by the pituitary. Tertiary...
Hyperthyroidism I: Introduction01:25

Hyperthyroidism I: Introduction

Hyperthyroidism is a type of thyrotoxicosis characterized by the thyroid gland's overproduction of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). This hormone excess increases the basal metabolic rate and enhances sensitivity to catecholamines.DiagnosisDiagnosis is based on clinical features and biochemical testing. It typically shows suppressed thyroid-stimulating hormone (TSH) levels below 0.4 mIU/L, with elevated free T3 and/or T4. Additional tests, including thyroid...
Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers

Class I antiarrhythmic drugs are used to treat various types of arrhythmias or irregular heart rhythms. These drugs block the sodium (Na+) channels in the cardiac cells, thereby affecting the movement of electrical impulses across the heart. Class I antiarrhythmic drugs are divided into three subgroups: Class IA, Class IB, and Class IC, each with distinct mechanisms of action and effects on the heart.
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...
Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers01:24

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which indirectly block calcium...

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Related Experiment Video

Updated: May 13, 2026

Zebra II as A Novel System to Record Electrophysiological Signals in Zebrafish
06:15

Zebra II as A Novel System to Record Electrophysiological Signals in Zebrafish

Published on: August 16, 2024

[Thyroid dysfunction and amiodarone].

Jandira Lima1, Patrícia Carvalho, M Auxiliadora Molina

  • 1Serviço de Medicina Interna dos Hospitais de Universidade de Coimbra, Faculdade de Medicina, Universidade de Coimbra, Coimbra, Portugal. limajandira@gmail.com

Arquivos Brasileiros De Endocrinologia E Metabologia
|February 27, 2013
PubMed
Summary

Amiodarone can cause thyroid dysfunction, with hypothyroidism more common than hyperthyroidism. Hyperthyroidism due to amiodarone is potentially fatal and requires vigilant monitoring.

Related Experiment Videos

Last Updated: May 13, 2026

Zebra II as A Novel System to Record Electrophysiological Signals in Zebrafish
06:15

Zebra II as A Novel System to Record Electrophysiological Signals in Zebrafish

Published on: August 16, 2024

Area of Science:

  • Cardiology
  • Endocrinology
  • Pharmacology

Context:

  • Amiodarone is an antiarrhythmic drug with significant potential for thyroid dysfunction.
  • Thyroid dysfunction can manifest as amiodarone-induced hyperthyroidism (HPEAI) or hypothyroidism (HPOAI).

Purpose:

  • To retrospectively analyze ten patients experiencing amiodarone-induced thyroid dysfunction.
  • To characterize the clinical presentation, subtypes, and management of HPEAI and HPOAI.

Summary:

  • Hypothyroidism (HPOAI) was more common (six patients) than hyperthyroidism (HPEAI) in this cohort.
  • HPEAI presented with various subtypes (1, 2, and 3), with arrhythmia exacerbation being a frequent symptom.
  • Treatment strategies varied, with levothyroxine for HPOAI and antithyroid drugs/corticosteroids for HPEAI.

Impact:

  • Amiodarone-induced hyperthyroidism (HPEAI) is associated with significant mortality.
  • Vague clinical presentations necessitate mandatory thyroid monitoring in patients on amiodarone.