Massive levothyroxine ingestion in a pediatric patient: case report and discussion

Abstract

We describe the course of a toddler who ingested a massive amount of levothyroxine and review treatment options for such overdoses. A 2K-year-old boy presented shortly after an ingestion of up to 7.6 mg of levothyroxine (potentially as much as 700 mg/kg). He was initially asymptomatic, treated with oral charcoal 1 g/kg, and discharged home from the emergency department after a few hours. He returned approximately 24 hours later with a temperature of 38.5uC, heart rate of 163 beats per minute, respiratory rate of 30 breaths per minute, and blood pressure of 136/70 mm Hg. He had a slightly decreased appetite and no signs or symptoms of infection. He was admitted to hospital and treated with oral acetaminophen. The initial free thyroxine (T 4 ) was . 100 pmol/L and free triiodothyronine (T 3 ) was 35.3 pmol/L. The patient had desquamation of the palms and soles, hair loss, and irritability during the month following the ingestion. Resolution of the elevated free T 4 occurred by 12 days post-ingestion and normalization of the thyroid-stimulating hormone by 7 weeks post-ingestion. There were no longterm sequelae. Levothyroxine overdose can result in significant complications, including seizures and arrhythmias, both of which should be monitored for. However, as our case illustrates, massive ingestion of levothyroxine in children typically follows a benign course.

American Thyroid Association Guide to Investigating Thyroid Hormone Economy and Action in Rodent and Cell Models

“…For example, 100 nM total T 3 in 0.5% BSA would give an estimated free T 3 concentration of around 3500 pM; for comparison, the free T 3 concentration of euthyroid human serum would be closer to 3-8 pM (about 1000 times lower). Even severely thyrotoxic patients would not be expected to achieve such high free T 3 concentrations, only reaching values of about 20 pM (283), or as high as 35 pM in the case of an accidental ingestion of a massive dose of L-T 4 (284). Some investigators have suggested that pharmacologic dosing can artificially enhance nongenomic and hypothetical off-target effects of T 3 ; if these are not a concern, the dose can be maximized for effect.…”

First episode of seizure in a 10-year old

“…A case report described an accidental ingestion of 700 µg/kg with a free T4 level > 100 pmol/L that did not result in seizures (3). Our patient had a smaller ingestion with a lower T4, reinforcing that dose and T4 levels do not correlate with the presence or severity of symptoms (1)(2)(3)(4). Symptoms can be delayed for several days after ingestion (1-4).…”

Complications of Hyperthyroidism

“…Most of the cases were related with Graves' hyperthyroidism [386][387][388]. Other aetiologic factors were massive levothyroxine ingestion [389], L-thyroxine treatment for hypothyroidism [390,391], subclinical hyperthyroidism [392] and Hashimoto's encephalopathy (HE) [393,394]. The pathophysiology of HE is not clear but increased antithyroid antibodies in all affected patients supports an autoimmune etiology.…”