Endocrine Abstracts

Background: Iodine deficiency is a well known cause of goitre and abnormal thyroid function but is rare in patients born in the UK. Iodine is primarily found in fish and dairy products and patients who avoid these foods may be at risk of iodine deficiency.

Case: A 22 year old gentleman was referred to endocrine clinic with an unusual pattern of thyroid function tests (TFTs). He had a goitre on examination. He had a background of irritable bowel syndrome and had minimal fish, fruit and vegetables and no dairy, bread or nuts in his diet. He had a normal TSH at 3.8 mU/l (0.2 to 4.5), low free T4 at 7 pmol/l (9 to 21) with raised free T3 at 5.7 pmol/l (2.5 to 4.9). The unusual pattern was confirmed at a second laboratory with a different immunoassay. Results were additionally confirmed following post-blocking tube, to remove antibody interference. Samples were sent to Addenbrooke’s laboratory for analysis and iodine deficiency was suggested as a possible cause. He underwent an ultrasound of thyroid which demonstrated mild global enlargement of the thyroid with reduced echogenicity and hypervascularity throughout. Opinion was appearances were abnormal but nonspecific. He was given dietary advice regarding sources of iodine and commenced Forceval. 2 months later his thyroid function had normalised. He stopped taking his Forceval but had recurrence of fatigue so recommenced his Forceval with symptoms resolving. His thyroid function has remained normal with adequate iodine supplementation.

Discussion: Iodine deficiency, whilst uncommon in the UK, can be a cause of abnormal thyroid function and goitre. Although it is rare, it should be considered in unusual patterns of TFTs, particularly in patients who have restrictive diets or dietary intolerances. Thyroid function can be normalised with dietary advice and supplementation if required.