This case of iodinated contrast media (ICM)-associated hyperthyroidism with the predominant clinical feature of atrial fibrillation (AF) with rapid ventricular rate (RVR) highlights that: (1) not all episodes of ICM-associated hyperthyroidism are mild or self-limiting, (2) whilst clinical features of hyperthyroidism may be limited, decompensation may occur, and (3) intervention should be considered and may be life-saving when features are not resolving.
An 82 year old lady presented with abdominal pain on a background including chronic myeloid leukaemia (CML), treated breast and colon adenocarcinoma, and atrial fibrillation. Contrast CT of the abdomen and pelvis, and subsequently neck and chest, confirmed lymphadenopathy and splenomegaly from CML progression. On day 14 she developed AF with RVR and diarrhoea. TSH was 0.1 mIU/L, T4 28.8 pmol/L, and T3 4.4 pmol/L. Carbimazole 10 mg daily, prednisolone, and metoprolol were commenced with good effect prior to discharge. Anti-thyroid antibodies were negative. Tc99m thyroid uptake was 0%. Ultrasound revealed no abnormalities. Urine iodine was significantly elevated (2216.4 mcg/24 hours).
Five days later she represented with tachycardia (150 bpm), abdominal pain and diarrhoea. Clinical examination demonstrated AF and mild peripheral tremor. Investigations confirmed T4 > 75 pmol/L, T3 7.9 pmol/L and mild pulmonary oedema. Burch-Wartofsky score 55. Treatment converted to propylthiouracil 200 mg QID, dexamethasone 4 mg BD, propranolol 40mg TDS and digoxin 125 mcg. After 4 days of stabilisation, treatment converted to carbimazole 20 mg BD and prednisolone 37.5 mg daily.
She remained biochemically hyperthyroid and had relapses of AF with RVR and decompensation on admission days 53 and 81. She then developed a hospital acquired pneumonia and subsequently transitioned to end-of-life-care.
ICM-associated hyperthyroidism is usually mild and self-limiting. [1] In retrospect, intervention with plasma exchange to reduce thyroid hormone levels prior to total thyroidectomy should have been pursued. [2, 3]