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Amiodarone Hypo or Hyper thyroidism?

8914 Views 9 Replies 5 Participants Last post by  ICARE
I've seen conflicting references about Amiodarone and it's effect on thyroid status.
What does it cause hypothyroidism or hyperthyroidism?
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In the begining it's effect is stimulatory ---- Hyperthyroidism
but later on it will inhibit the thyroid ------- Hypothyroidism
(Just like Iodine suppliment)
Can you explain the mechanism, I don't understand how Iodine cause hyper then hypo :(
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Amiodarone effects on TSH

I don't know if there is direct effect of Iodine on the TSH or TRH release, anyone knows about that??:confused:
Yes, Amiodarone has effects on TSH and TRH.

  • Amiodarone inhibits type 1 5'-deiodinase enzyme activity, thereby decreasing the peripheral conversion of T4 to triiodothyronine (T3) and reducing the clearance of both T4 and reverse T3 (rT3). Consequently, the serum levels of T4 and rT3 increase and the serum levels of T3 decrease by 20-25%.
  • Amiodarone inhibits entry of T4 and T3 into the peripheral tissue. Serum T4 levels increase by an average of 40% above pretreatment levels after 1-4 months of treatment with amiodarone. This, in itself, does not constitute evidence of hyperthyroidism (thyrotoxicosis).
  • Amiodarone causes inhibition of type 2 5'-deiodinase enzyme activity in the pituitary due to feedback regulation is seen in the first 1-3 months of therapy and leads to an increase in thyroid-stimulating hormone (TSH) levels. This is not an indication for T4 replacement in these patients. Serum TSH levels return to normal in 2-3 months as T4 concentrations rise sufficiently to overcome the partial block in T3 production. The response of TSH to thyroid-releasing hormone (TRH) may be reduced.
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I also would like to add that there are other 5' deiodinase enzyme inhibitors.
These are
Propyl thiouracil (at high doses) and Lithium :)
And also steroids :)
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