Acute poisoning with thyroxine in children

Two girls aged 5 and 14 years were admitted to hospital after ingestion of L-thyroxine in estimated doses of 72 micrograms.kg and 118 micrograms.kg in the preceding 4 and 8 hours, respectively. Both had high serum T4 (19 and 20 micrograms/dl) and were asymptomatic at the time of admission and both were treated with Iopanoic acid 3 g orally every 72 hours, in order to block the conversion of T4 into T3. Serum levels of T4 were still elevated for up to ten days (8 and 16 micrograms/dl, respectively at day 10), but serum levels of T3 came down to 60 micrograms/dl within the first 48 hours of treatment in both cases. It should be taken into account that these patients may be initially asymptomatic and that symptoms may appear even later than 24 hours after the ingestion, so they should be admitted and treated at hospital. Iopanoic acid has been proved to be a treatment of choice in order to block the conversion of T4 into T3.