amiodarone induced hypothyroidism
Last reviewed 03/2022
- incidence
- in areas with high iodine intake - 13%
- in areas of low iodine intake - 6.4%
- patients with low environmental iodine e.g. Italy develop more amiodarone
induced hyperthyroidism than amiodarone induced hypothyroidism - the opposite
occurs where there is high environmental iodine e.g. UK, USA
- diagnosis
- low T3, T4; increased TSH
- in the first three months of amiodarone therapy there may be a transient
increase in TSH levels
- treatment
- continue amiodarone therapy in combination with thyroxine therapy
Notes (1,2,3):
- about 37% of amiodarone contains organic iodine by molecular weight
- each 200 mg tablet is estimated to contain about 75 mg of organic iodide
of which 10% (7.5 mg) is de-iodinated to yield free iodine
- results in a high iodine supply to the body that far exceeds the daily recommended optimal iodine intake (0.2 to 0.8 mg)
- each 200 mg tablet is estimated to contain about 75 mg of organic iodide
of which 10% (7.5 mg) is de-iodinated to yield free iodine
- elimination half-life of amiodarone is about 2-3 months, and total body iodine stores may remain elevated for up to 9 months even after discontinuation of the drug
- amiodarone-induced thyroid dysfunction is a complex phenomenon; however, its exact pathogenesis largely remains unknown
Reference:
- BMJ 1999;319:894-99.
- Harjai KJ, Licata AA. Effects of amiodarone on thyroid function. Ann Intern Med. 1997;126:63-73
- Bogazzi F, Tomisti L, Bartalena L, Aghini-Lombardi F, Martino E. Amiodarone and the thyroid a 2012 update. J Endo-crinol Invest. 2012;35:340-8