Amiodarone does have an iodine base and can cause both hypothyroidism and hyperthyroidism. I am a cardiac nurse and I've seen either occur in many patients. It frequently causes the most problem by decreasing T4 to T3 conversion. T4 is a storage form of thyroid hormone and it has to be converted to T3 by the liver and peripheral tissues external to the thyroid gland itself. With amiodarone, the conversion process causes more Reverse T3(RT3) to be formed rather than the active form of T3. RT3 can block the receptor sites for T3 so it further decreases the amount of T3 action. I cannot find any documentation to support this, but I suspect that RT3 has the same effect on TSH as T3- it lowers it. So the bottom line is, amiodarone not only can make a person hypoth yroid but it can mask the evidence (TSH) so that the doctor sees no explanation for all of those horrible hypothyroid symptoms. A well respected electrophysiologist (cardiologist who specilizes in heart rhythm problems) in my hospital said that you have to rely on TSH in patients on amiodarone because RT3 gives false readings for the other tests. I think this is wrong but the literature that I can find always says the TSH is the best thing to monitor in patients on amiodarone. I think it seems reasonable that free T3 would give the most accurate result. I think total T3 can include both active T3 and RT3 but free T3 may not. If either test is skewed, it is skewed to appear higher (due to RT3) than it really is. So if either test is low, it would be appropriate to increase the thyroid dose. For obvious reasons, T3 meds would be better because conversion (which is faulty anyway) is bypassed. How ever, most doctors fear T3 meds due to an increased risk of arrhythmias and this would be true in your case also. I believe you when you say that your arrhythmias come from being hypo. I think this has something to do with the adrenal glands trying to compensate for the low thyroid. Also, in hypothyroidism, the heart muscle does not contract or relax as effectively as it should. This can cause some stretching of the heart muscle and conduction fibers which can certainly lead to some abnormal heart rhythms. These are supposedly reversible effects once the thyroid hormones are optimized. Hypothyroidism as a cause of rhythm problems does not seem to be appreciated by most doctors including cardiologists. The texts say that hyPERthyroidism causes arrhythmias and they don't seem to think beyond that. There are many different types of heart rhythm abnormalities that can occur. If your type was not life threatening (and it d oesn't sound like it was) then I'd try to get off of amiodarone. It can have other serious side effects too such as lung toxicity. Be aware that it takes several months for amiodarone to completely leave your tissues after it is discontinued. Nancy _______________________________________________________________ Control Your Self-Serve Thyroid Account Here Rules - mailto:[log in to unmask] NoMail - mailto:[log in to unmask] Mail - mailto:[log in to unmask] Not DAILY DIGEST - mailto:[log in to unmask] DAILY DIGEST - mailto:[log in to unmask] Stop Attachments - mailto:[log in to unmask] Force Attachments - mailto:[log in to unmask] Force Subject: [THYROID] - mailto:[log in to unmask] Subscribe - <http://maelstrom.stjohns.edu/CGI/wa.exe?SUBED1=thyroid> Unsubscribe - mailto:[log in to unmask] Our Home Page - http://www.Emissary.Net/thyroid/index.html Thyroid Archives - http://maelstrom.stjohns.edu/archives/thyroid.html Contact List Owners - mailto:[log in to unmask] _______________________________________________________________