Endocrine Abstracts

Background: Amiodarone-induced thyrotoxicosis (AIT) is sometimes very difficult to treat. Pulse methylprednisolone in addition to oral steroids appears effective in treatment of AIT, but effects of such treatment may be transient.

Presentation of The Case: A 65 year old man was admitted our Department because of drug-resistant AIT. He had a history of atrial fibrillation, treated with amiodarone since 2019, and NSTEMI myocardial infarction (2020). In 2022 he had suffered another NSTEMI and was found to be thyrotoxic (TSH<0.005 uIU/ml, free T3 (fT3) 22.43 pmol/l (3.1-6.8), free T4 (fT4)>100 pmol/l (12-22)). Amiodarone was stopped, but he failed to respond to thiamazole (20 mg tds). On admission he had episodes of confusion and hypotension (about 80/60 mmHg) associated with rhythms above 130/minute. He was markedly thyrotoxic: fT4>7.77 ng/dl (0.93-1.7), fT3 14.95 pg/ml (2-4.4). Thyroid ultrasound was unremarkable, while titres of all anti-thyroid antibodies were normal. He was treated with thiamazole 20 mg tds, prednisolone 40 mg od and pulse methylprednisolone 500 iv and then 250 mg iv once a week. After six doses his fT3 decreased to 2.05 pg/ml and fT4 to 2.41 ng/dl. Methylprednisolone was stopped. After about three weeks (despite continuation of thiamazole and prednisolone) he presented with rebound thyrotoxicosis: fT4>7.77 ng/dl, fT3 5.46 pg/ml. Methylprednisolone was restated (500 mg and then five doses of 250 mg) that was followed by a decline in fT4 to 2.51 ng/dl and fT3 to 1.92 pg/ml. He subsequently underwent successful thyroidectomy - one week post thyroidectomy fT4 0.92 ng/dl, fT3 1.3 pg/ml, TSH 0.06 uIU/ml.

Conclusions: Pulse intravenous methylprednisolone may be a useful adjunct therapy in cases of refractory amiodarone-induced thyrotoxicosis, but there is a danger of a rebound worsening of thyrotoxicosis after discontinuation of this therapy.