Endocrine Abstracts

Case report: A 41-year-old lady, previously diagnosed with Graves’ disease, had been treated with 12 months carbimazole in a standard block and replace regimen. The hyperthyroidism relapsed following treatment withdrawal so she was treated definitively with radio-iodine therapy, remaining well for 5 years, without hypothyroidism. The patient commenced the lighter life diet due to weight gain and subsequently presented with weight loss of a stone and atrial fibrillation (AF). She was found to have relapsed hyperthyroidism (FT₄ 45 pmol/l, TSH suppressed.) The lighter life diet involves combined group counselling sessions and a very low calorie diet (VLCD) constituting pre-prepared food packs (shakes and mousses). The food supplements are documented to contain iodine, between 90 and 117.5 μg/100 g dependant on the snack or meal used. (~110 μg/day). On admission, serum iodine levels were elevated at 0.93 μmol/l (0.32–0.63).

Discussion: Iodine has a central role in thyroid hormone synthesis (recommended daily intake of 50 μg). Whilst both iodine deficiency and excess can cause thyroid dysfunction, iodine-induced hyperthyroidism (IIH) is commoner in areas of iodine deficiency or in patients with pre-existing thyroid disease. IIH is usually self-limiting (lasting 1–18 months) if the source of iodine is eliminated but thionamide treatment may speed recovery. Other sources of inadvertent iodine supplementation include multivitamin preparations, cough medicines and iodinated contrast media used in CT scanning/angiography. Detailed history of potential iodine ingestion is required in all hyperthyroid patients.

Outcome: The patient was treated with β blockers for the AF, which settled, and started with titratable dose carbimazole which was discontinued after 6 months. She remains euthyroid 6 months off treatment (and off iodine supplementation).