Endemic goitre and hypothyroidism in an adult female patient dependent on total parenteral nutrition

We present the case of a thirty-year-old female patient who was referred to the endocrinology team with an enlarging goitre and biochemical hypothyroidism. She had been dependent on total parenteral nutrition for the previous six years as a result of intestinal failure thought to be caused by possible underlying mitochondrial disease. The patient also suffers from a Desmin myopathy, and at present, the exact aetiology behind her intestinal failure is not certain. The goitre was smooth and had been enlarging slowly over the previous few months. Thyroid peroxidase antibodies were found to be within normal range. Further analysis of the case showed that twelve months earlier the patients total parenteral nutrition (TPN) feed had been altered as a result of manganese toxicity. The current feeding regimen did not contain a trace element additive which had previously supplied iodine supplementation. A little detective work established that iodine content to the TPN had been reduced, the trace element additive (Additrace) was recommenced providing 1 µmol of iodine per day, equating to 130 µg of iodine. Following this change, thyroid-stimulating hormone levels returned to normal and the goitre quickly reduced in size. We present a rare case of endemic goitre and hypothyroidism in a patient receiving inadequate iodine supplementation through total parenteral nutrition. LEARNING POINTS: Endemic goitre and hypothyroidism secondary to iodine deficiency are rare in the developed world. However, the diagnosis should be considered in the setting of a diffuse goitre and negative thyroid antibodies. Although rare, endemic goitre should be considered in patients who present with hypothyroidism and who are dependent on total parenteral nutrition. Treatment with levothyroxine is not required in endemic goitre as thyroid function tests generally normalise with the addition of iodine to the diet/total parenteral nutrition regimen. Iodine supplementation at a level recommended by the European Society for Clinical Nutrition and Metabolism (ESPEN) was observed to quickly normalise this patient’s thyroid function tests.