Endocrine Abstracts

Background: Amiodarone-induced thyrotoxicosis is sometimes extremely difficult to treat necessitating emergency thyroidectomy with perioperative risks including possible thyroid storm. We obtained near normalization of free T3 (FT3) by pulse Methylprednisolone prior to thyroidectomy for drug-resistant Amiodarone-induced thyrotoxicosis.

Case Description: A 56 year old man (BMI 29.7 kg/m²), with history atrial flutter/fibrillation, episodes of fast AF~200/minute, after unsuccessful ablation therapy, presented with severe Amiodarone-induced thyrotoxicosis, unresponsive to high dose oral Thiamazole (40 mg/day). On admission his FT3 was 24.59 pg/ml (ref. range 2.0-4.4), free T4 (FT4)>7.77 ng/dl (ref. range 0.93-1.7), TSH<0.005 uIU/ml. All anti-thyroid antibodies were negative. Thyroid ultrasound revealed normal size thyroid without focal lesions. He initially responded to high dose intravenous Thiamazole (40 mg tds), Lithium Carbonate (250 mg tds) and oral Prednisolone (60 mg od) i.e. after 11 days his FT3 was 5.4 pg/ml, FT4 4.96 ng/dl, but after change to oral thiamazole (20 mg tds), there was a rebound increase of FT3 (to 9.6 pg/ml), and FT4 (to 6.14 ng/dl). Re-administration of intravenous Thiamazole prevented an increase in FT3, but there was further increase in FT4 (>7.77 ng/dl). On 24^th day of admission he was therefore referred for emergency thyroidectomy. Administration of 500 mg of intravenous Methylprednisolone (on a background of oral Prednisolone) within 48 hours resulted in a decrease in FT3 from 9.53 pg/ml to 6.03 pg/ml (2.0-4.4) i.e. only 37% above upper reference range. Following administration of two units of fresh frozen plasma (in order to enhance further thyroid hormone binding) he underwent successful total thyroidectomy (9 days post-surgery: TSH 0.005 uIU/ml, FT3 0.99 pg/ml, FT4 1.16 ng/dl).

Conclusions: Pulse intravenous Methylprednisolone may be a useful adjunct therapy for preparation for thyroidectomy in cases of drug-resistant Amiodarone-induced thyrotoxicosis.