Background: There are published recommendations for neonates to avoid exposure to iodine. Iodine is trapped by the thyroid gland from the blood stream and used for the synthesis of thyroid hormones. Any excess is excreted almost entirely in the urine. Acute kidney injury, especially anuria places infants at risk of toxicity when exposed to iodine and paradoxical hypothyroidism can occur (WolffChaikoff effect). Hypothyroidism of sufficient severity to seriously put the brain at risk has been reported. The paediatric nephrology community have taken appropriate precautions and this problem stimulated an alert by Medicines and Healthcare products Regulatory Agency in the UK. However, we describe a case where this has occurred again.
Objective and hypotheses: To describe a case of severe hypothyroidism secondary to iodine toxicity.
Method: A male infant born at 38 weeks with autosomal recessive polycystic kidney disease requiring bilateral nephrectomies and continuous peritoneal dialysis on day 7 of life was studied.
Results: Newborn screening result for hypothyroidism revealed a blood spot TSH of 7.5 mu/l, that would have been accepted by many screening programs as normal. This was repeated, as our centre has a cut-off point of 5 mu/l for further attention. Peritoneal dialysis had been established for 24 days when hypothyroidism was confirmed with plasma free T4, 6.0 pmol/l (ref 1025) and TSH 312 mU/l (ref 0.33.8). Ultrasound demonstrated a normally sited thyroid. The dialysis catheter cap used for long-term dialysis contains iodine as an antimicrobial. The peritoneal dialysate fluid iodine concentration, 13.3 μmol/l, was significantly higher than a paired plasma iodine concentration of 3.1 μmol/l (NR 0.320.62). 50 μg thyroxine daily normalised thyroid function. Dialysis was adjusted to reduce to infusion of iodine contaminated dialysis fluid.
Conclusion: Peritoneal dialysis, using iodine impregnated dialysis caps, places a neonate at risk of serious hypothyroidism and thyroid function must be checked.
20 - 22 Sep 2014
European Society for Paediatric Endocrinology