Thyroid dysfunction during chronic amiodarone therapy

Abstract

Clinical and laboratory features of 99 patients receiving long-term amiodarone therapy were analyzed to determine which individuals may be at a high risk for developing amiodarone-induced thyroid dysfunction. The group of 68 men and 31 women was followed up for an average of 27 months (range 3 to 60). There were no differences in age, sex, dose of amiodarone, type or severity of underlying heart disease or baseline serum thyroxine levels in patients who developed hypothyroidism (n = 32) or hyperthyroidism (n = 5) or remained euthyroid (n = 62). Baseline serum thyrotropin levels were statistically higher in patients who became hypothyroid, but there was considerable overlap with the other patient groups. Serum reverse triiodothyronine (reverse T3), which has been suggested to be a marker of amiodarone efficacy, correlated directly with serum thyroxine levels, and was not an independent variable. There was no pattern to the time course for development of thyroid dysfunction, which occurred in 49% of those followed up and developed as early as 1 month or, in one individual, as late as after 3 years of amiodarone therapy. There are few guidelines for replacement therapy in patients with amiodarone-induced hypothyroidism. L-thyroxine dosage was adjusted cautiously in these high risk individuals to achieve serum thyroxine levels within the reference range of euthyroid individuals taking amiodarone: the mean dosage required was 136 micrograms/day. Normalization of serum thyrotropin (TSH) would have required doses of L-thyroxine that were judged to be excessively high.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiodarone-Associated Thyroid Dysfunction

“…11 Male patients predominated in other studies, and the mean ages of the study populations were 54 to 66 years, compared with 34.9 years in the present study. 1,2,8,9 Although age was not demonstrated to be a risk factor for thyroid dysfunction within this study, it is possible that the relative youth of our patients does confer a risk greater than that found in studies of patients Ͼ60 years old.…”

“…1,8,9 Of interest, amiodarone appears to induce thyroid dysfunction in children only rarely, perhaps reflecting the low incidence of primary thyroid disease in children. 10 The case-control analysis did not examine duration of amiodarone therapy as a risk factor for thyroid dysfunction, but there appeared to be no difference in median duration of therapy between those who developed thyroid dysfunction and those who remained euthyroid.…”

Amiodaron i tarczyca

“…Many patients without pre-existing thyroid disease become euthyroid within 2-4 months after quitting AMIO treatment. Because of AMIO effects on thyroid hormone metabolism, higher doses of T4 may be required [100,101]. Particular caution is warranted to avoid overtreatment, in view of the frequent severe underlying cardiac problems.…”

“…Wielu pacjentów bez wcześniejszej choroby tarczycy po zaprzestaniu stosowania AMIO uzyskuje eutyreozę w ciągu 2-4 miesięcy. Ze względu na fakt, że AMIO wpływa na metabolizm hormonów tarczycy, w leczeniu mogą być wymagane wyższe dawki tyroksyny [100,101]. Szczególnie należy zachować ostrożność u chorych z ciężkimi chorobami serca ze względu na możliwość powikłań kardiologicznych związanych ze stosowaniem zbyt dużych dawek tyroksyny.…”

Disfunción tiroidea inducida por amiodarona en la práctica clínica

“…Si la AMD no puede ser descontinuada, LT4 restaura el eutiroidismo bioquímico, con resolución de síntomas. La terapia con LT4 se inicia con dosis bajas de 25 a 50 ug/d, y se va incrementando lentamente hasta que la TSH retorne a lo normal (14) . La dosis de LT4 necesaria para normalizar TSH puede ser mayor en los pacientes con HIA comparados con los pacientes portadores de hipotiroidismos convencionales; posiblemente como resultado de la producción disminuida de T3 intrahipofisiaria, debido a la inhibición de la 5' deiodinasa tipo 2.…”