IDD NEWSLETTER NOVEMBER 2014 ID IN CANADA 15

Severe iodine deficiency in a Canadian boy with food allergies

Excerpted from: Pacaud D et al. A third world endocrine disease in a 6-year-old North American boy. Journal of Clinical Endocrinology and Metabolism. 1995; 80(9): 2574–2576

A 6-year-old French-Canadian boy was seen for symptoms of goiter and hypothyroidism of acute onset. He was referred to the endo- crinology clinic with a 3-month history of fatigue. Severe asthma and atopic dermatitis had started during infancy. The boy had multiple food allergies. His diet was very restricted and consisted of oat cereal, horse meat, broccoli, sweet potatoes, cauliflower, grapes, apples, and water. His thyroid was diffusely increased in size. Thyroid function tests revealed severe primary hypothyroidism with undetectable antibodies. Physical exam showed several classic signs of hypothyroi- dism: facial edema was noticeable, and the skin felt very dry and was eczematous.

Investigations and treatment liz west/flickr, 2012; CC BY 2.0 Normal bone age and growth rate suggested Cruciferous vegetables contain thiocyanate which together with iodine deficiency may lead to goiter that the hypothyroidism was of acute onset. A nutritional investigation showed low Discussion In conclusion, this boy suffered from caloric intake and low urinary iodine levels Since the introduction of iodized table salt goitrous hypothyroidism secondary to severe indicative of severe iodine deficiency. Initial in North America, severe iodine deficiency iodine deficiency and compounded by thi- treatment with levothyroxine resulted in has been practically eradicated. The boy’s ocyanate overload. Thus, even in our envi- the resolution of clinical hypothyroidism, a severe goitrous hypothyroidism was the ronment of relative iodine abundance, IDD reduction of thyroid volume, and normali- result of an extremely restricted diet used and possibly other nutritional deficiencies zation of thyroid function tests, but urinary to control severe atopy. His caloric intake should be suspected in patients using special iodine remained undetectable. When the was maintained with very large amounts of diets prescribed by physicians or in patients treatment was stopped for four months, the sweet potatoes, cauliflower, and broccoli. practicing alternative nutrition (3). symptoms returned, and the boy was trea- These vegetables contain thiocyanate (SCN-) ted with a daily dose of 90 µg of potassium and cyanoglucosides, two substances known References iodide (recommended by WHO/UNICEF/ to be goitrogenic (2). The goitrogenic effect 1. WHO/UNICEF/ICCIDD. Indicators for asses- ICCIDD) (1). After a temporary dose in- of iodine deficiency is amplified by simulta- sing iodine deficiency disorders and their control through salt iodization. Geneva: WHO; 1994 crease, the boy’s urinary iodine excretion neous thiocyanate excess. It should be noted 2. Delange F. The disorders induced by iodine defi- normalized, and he continues to do well that once iodine stores are replenished, a ciency. Thyroid. 1994; 4:107–128 on 90 µg/day. threshold iodine intake of only 90 µg will 3. Kanaka C, et al. Risks of alternative nutrition in correct iodine deficient hypothyroidism, infancy: a case report of severe iodine and carnitine even if SCN- overload persists. deficiency. Eur J Pediatr. 1992; 151: 786–788