Endocrine Abstracts

JOINT175

Introduction: Amiodarone induced thyrotoxicosis (AIT) is characterized by thyroid over-activity in context of current/recent amiodarone use. It is sub-divided mainly into 2 types; Type 1 AIT occurs due to amiodarone’s high iodine content causing increased thyroid hormone production, whereas Type 2 AIT is a form of destructive thyroiditis resulting in excessive thyroid hormone release. Distinguishing these sub-types is based on biochemical and radiological parameters, which helps guide treatment.

Case-report: A 69-year-old gentleman with known chronic renal impairment, ischemic heart disease with moderate left ventricular impairment, severe aortic stenosis, a previous out of hospital cardiac arrest, and a long-standing amiodarone use history presented in cardiogenic shock and type 2 respiratory failure. He was intubated and taken to the intensive care unit where he was noted to be thyrotoxic with a TSH of <0.01, T4 of >64, and T3 of 10.9, which was believed to be contributing to his initial presentation. He was commenced on Propylthiouracil (PTU) 200 mg TDS and prednisolone 40 mg daily. TSH receptor antibody titre was 0.4 U/l (range <0.4) and a thyroid doppler USS showed absence of hypervascularity consistent with Type 2 AIT. Following brief improvement, thyroid hormones incremented further, prompting a change of PTU to carbimazole 20 mg TDS. During this time the patient was extubated and transferred for an inpatient Transcatheter aortic valve insertion (TAVI) for aortic stenosis. He however remained thyrotoxic, therefore the prednisolone dose was escalated to 60 mg daily. The admission was complicated by urosepsis and a hospital acquired pneumonia, which drove further relapse in thyroid status. Total thyroidectomy was considered however deemed risky given the patients’ cardiac background. A combination of PTU 200 mg TDS, carbimazole 20 mg TDS, and prednisolone 60 mg daily was utilized, and over the coming weeks, T3 and T4 levels steadily declined, allowing the TAVI to proceed. Subsequently PTU and carbimazole were gradually discontinued, and prednisolone was weaned to 40 mg daily. Thyroid function improved revealing a TSH of 0.04, T4 of 16.9, and T3 of 3.7.

Discussion: A combination of steroids and anti-thyroid drugs are typically used in AIT as diagnostic obscurity/overlap often exists. Due to amiodarone’s long half-life, AIT may occur months after discontinuation, and therefore discontinuing amiodarone acutely can not only be challenging from a cardiac standpoint, but may offer little immediate benefit from a thyroid perspective. Total thyroidectomy may be considered in cases of treatment resistant AIT however this was deemed risky in our case given the patient’s cardiac background.