Endocrine Abstracts

Background: AIT type 2 is self-limiting in nature and therefore discontinuation of amiodarone may not be necessary; however, the feasibility of continuing amiodarone has never been tested formally. Potassium perchlorate (KClO₄) may have advantage when prednisone is unsuccessful in AIT type 2, possibly due to mixed cases of types 1 and 2. KClO₄ also mitigates the cytotoxic effect of desethylamiodarone on thyrocytes in vitro.

Objectives: i) To demonstrate the feasibility of continuation of amiodarone in AIT type 2.

ii) To evaluate if KClO₄ is useful in AIT type 2, given either alone or in combination with prednisone (to shorten time to euthyroidism).

Patients: We included patients with AIT type 2 (TSH<0.1 mU/l+FT₄>25 pmol/l, TPO-Ab<50 kU/l, TBII<2.0 kU/l, poor or no visualisation of thyroid gland on 99mTc-pertechnate scintigraphy, no nodular goiter on ultrasound) in whom amiodarone was continued. Exclusioncriteria: severe co-existent illness, no informed consent.

Research design and methods: Randomised multicenter study, central randomisation in 3 treatment arms: i) 30 mg prednisone/day+30 mg methimazole/day, ii) 500 mg perchlorate 2×/day+30 mg methimazole/day, iii) 30 mg prednisone/day+500 mg perchlorate 2×/day+30 mg methimazole/day. If thyrotoxicosis persisted after 12 weeks of treatment, perchlorate was added in group A and prednisone in group B. In all groups amiodarone was continued. Total follow up time was 24 months.

Results: Fifty-six patients were registered of whom 42 patients randomised. 9 had no inclusion criterion (5 FT₄<25 pmol/l, 3 because the cardiologist preferred to stop amiodarone, 1 AIT type 1). Five were excluded (4 no informed consent, 1 severe co-existent illness). Six were excluded after randomisation (3 high TBII or TPO-Ab, 2 because amiodarone was inadvertently withdrawn, 1 emigration). Thirty-six patients completed the study (12 group A, 14 group B, 10 group C). Euthyroidism ensued in all patients. Mean time to euthyroidism was shortest in group A (11 weeks; group B 14.9 and group C 13.2). Secondary therapy was required in 4 patients (group B) and recurrent thyrotoxicosis occurred in 5 (1 group A, 1 group B, 3 group C). There were no severe side effects.

Conclusions: Continuation of amiodarone is feasible in AIT type 2. Continuation of amiodarone after successful treatment of AIT type 2 is associated with 14% recurrences in 2 years. Treatment with prednisone is preferable to perchlorate and adding perchlorate to prednisone does not shorten time to euthyroidism in AIT type 2.