Amiodarone-induced thyrotoxicosis do anti-thyroid drugs alone provide adequate treatment?

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 437-470-Non-neoplastic Thyroid Disorders
Basic/Clinical
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-453
Nadia Patel*, Gerald Kaye, Warrick J Inder and Clair Sullivan
Princess Alexandra Hospital, Woolloongabba QLD, Australia
Introduction: Amiodarone-induced thyrotoxicosis (AIT) occurs in 3-12% of patients receiving amiodarone.  We aimed to compare the efficacy of antithyroid drugs (ATD) alone versus ATD and prednisolone (ATD+PRED) in the treatment of AIT in a tertiary hospital setting.

Methods: The management of AIT was reviewed in 32 patients, mean age 62.7 years (range 35-81 years). Treatment was commenced according to the judgement of the treating endocrinologist. Five patients with mild hyperthyroidism were not commenced on any treatment (NIL). The main outcome measures were time to euthyroidism and number proceeding to thyroidectomy.

Results: Of those treated initially with ATD, 9/14 (64%) required the addition of PRED due to inadequate response (n=8) or adverse event to ATD (n=1). Baseline fT4 was significantly higher in those ultimately treated with ATD+PRED (n=22, 56.2±6.0 pmol/l) vs those treated with ATD or NIL (n=10, 28.3±3.1 pmol/l), P=0.005. Similar results were seen with fT3. There was a significant correlation between the initial dose of ATD and baseline fT4, r=0.49, P=0.01. In patients with baseline fT4 <30 pmol/l, 75% (6/8) achieved euthyroidism without PRED.

Twelve patients (37.5%) proceeded to thyroidectomy, 9 because of failure to achieve euthyroidism and 3 prophylactically before restarting amiodarone. The baseline fT4 was higher in the group requiring thyroidectomy, 60.6±10.3 pmol/l vs those not requiring surgery (n=20, 39.6±3.8. P=0.031). Thyroidectomy was safely undertaken in all patients with 0% mortality and no major morbidity.

In those not requiring surgery, there was no difference in final time to fT4 or TSH normalisation between those receiving ATD+PRED (fT4 16.1±2.7 weeks, TSH 21.0±4.0 weeks), vs ATD alone or NIL (fT4 17.4±3.1 weeks, TSH 29.6±5.6 weeks). Fourteen (70%) became euthyroid off all medication, 3 (15%) required ongoing anti-thyroid drugs, 1 (5%) developed hypothyroidism and 2 (10%) were lost to follow up. Two patients later died from causes unrelated to their thyroid disease. 

Discussion: In patients with AIT, those with higher fT4 and fT3 levels generally require glucocorticoids. The similar time to achieve euthyroidism between the groups is probably due to greater disease severity in the ATD+PRED group. Mild disease (fT4 <30pmol/l) may be successfully treated with ATD alone. Thyroidectomy in those responding poorly to medical therapy resulted in a uniformly good outcome.

Nothing to Disclose: NP, GK, WJI, CS

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