Endocrine Abstracts

Case history: A 30-year old female presented with a 10-month history of enlarging neck mass, fatigue and weight gain. Assessment by her GP found her to have a large smooth goitre and biochemical hypothyroidism. The patient had a history of intestinal failure secondary to mitochondrial disorder. As a result of intestinal failure she was entirely dependent on parenteral nutrition and was intolerant of any oral intake, with venting of her stomach to reduce pain. She was referred to endocrinology for consideration of intravenous thyroid hormone replacement. It was noted that her anti-TPO Abs were negative, and the aetiology of her hypothyroidism unclear. Subsequent enquiry revealed that 18 months prior to presentation the TPN regimen had been changed with the removal of the vitamin and mineral supplement, Additrace. Thus the patient was not receiving iodine in her feeding regimen. Vitamin supplementation was recommenced with adequate iodine. The patients goitre reduced in size and TFTs returned to normal within 2 months. Thyroid hormone replacement was not required.

Investigations: TSH, fT4, fT3, and TPO Abs were measured.

Results and treatments: Initial TFTs showed TSH 8.2 mIU/l (0.2–4.2) and fT4 5.9 pmol/l (11.0–22.0). TFTs were repeated with anti-TPO Abs and these showed TSH 25.0 mIU/l, free T4 3.1 pmol/l and TPO Abs <28 u/ml. Free T3 was within normal limits. The patient received treatment with Additrace. It contains a number of trace elements and vitamins, including iodine. The patients daily iodine supplementation was 1 umol once Additrace was commenced. After iodine supplementation was added to the TPN regimen, TSH normalised to 1.3 mIU/l within 2 months of treatment. The goitre resolved completely.

Conclusions and points for discussion: Iodine deficiency is widespread in the developing world and is a leading cause of hypothyroidism, though rarely seen in developed countries. There are few cases in the medical literature of endemic goitre and hypothyroidism in adults receiving TPN. This case highlights the importance of iodine supplementation in patients with no oral intake, and the importance of considering iodine deficiency within the differential diagnosis of hypothyroidism.