Endocrine Abstracts

A 15 year old male presented to paediatric endocrinology with a large goitre and a thyroid function test confirming fT4 4.4 pmol/l and TSH 3.0 mU/l. Previous medical history included lifelong atopic eczema and multiple food allergies which had led to the exclusion of nuts, dairy products, eggs and fish from his diet. Autism spectrum disorder had been diagnosed at 4½ years of age. Two subsequent thyroid function tests were unchanged and thyroid auto-antibodies were negative. Secondary hypothyroidism due to isolated TSH deficiency was considered as basal pituitary function was otherwise normal as was MRI of pituitary. Treatment with levothyroxine 50 µg od normalised thyroid function. Thyroidectomy was advised but the patient had declined. At transition to adult endocrinology care at 17 years of age a diagnosis of iodine deficiency was considered on the basis of a large goitre and initial thyroid function tests. Further investigations confirmed normal basal pituitary function and severe iodine deficiency (urinary iodine concentration 150.70 nmol/l and iodine:creatinine ratio 8.41 nmol/mmol). CT imaging confirmed a large goitre (right lobe 4.3 x 2.7 x 7.0 cm and left lobe 3.8 x 2.9 x 7.2 cm) with a total volume of 160.6 ml. Following counselling on the possibility of hyperthyroidism levothyroxine was stopped and treatment with iodine 150 µg od commenced which resulted in maintenance of normal thyroid function with rapid decrease in goitre size. There are only eight previous cases in the world literature of similar dietary restriction resulting in goitre and impaired thyroid function in paediatric age group patients. Diagnosis of autism was made in three of the cases indicating a possible role for iodine deficiency in this condition. This case reinforces the suggestion made by previous authors that children with such dietary restriction should be monitored for iodine deficiency.