Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, India.
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Two sisters, aged 3 and 1 years, were brought to the casualty with history of consumption of levothyroxine tablets. Their mother had hypothyroidism and was on levothyroxine. The mother found the two children playing with the levothyroxine bottle (75 mcg tablets). The exact number of tablets of levothyroxine ingested by each sibling was uncertain, but 50 tablets were reported to be missing. The elder sibling received gastric lavage with charcoal within 1 hour of ingestion and was referred to our center for further management. Since the physical examination at the time of reporting to our hospital was unremarkable, the danger signs were explained to the parents and they were advised close follow-up. The parents reported to the casualty on day 3 of ingestion, with complaints of increased precordial activity in the elder child. Child was afebrile, but had tachycardia (heart rate 136/min). ECG showed sinus tachycardia. The total T₃ and T₄ levels were elevated: levels of thyroid stimulating hormone were low (Table I). Child was started on propranolol 1 mg/kg/day. Tachycardia settled 7 days after propranolol was started and the drug was subsequently stopped. The serial fT3, fT4 and TSH levels are summarized in Table I. The younger sibling was symptom-free at presentation and on subsequent follow ups.

TABLE I  Serial Thyroid Function Tests After Levothyroxine Ingestion

Children with levothyroxine overdose may have symptoms like fever, flushing, palpitations, increased sweating, tremors, irritability, increased bowel movements and convulsions. They may have tachycardia, hypertension and cardiac arrhythmias [1]. Levothyroxine overdose in children typically follows a benign course [2]. The onset of symptoms may be delayed up to 11 days after ingestion of a massive dose of levothyroxine ingestion, given the half life of levothyroxine of approximately 7 days [1]. Propranolol is used to reduce the symptoms. In severely symptomatic patients, steroids and propylthiouracil can be used [3]. In patients with significant cardiac or neurological symptoms, extractive techniques (charcoal hemoperfusion and/or plasmapheresis) have been used in the past [4, 5].

Levothyroxine is available in various colored tablets and has no noxious taste making it attractive to children. Adults who are on thyroid hormone supplements should always be cautioned to keep these tablets beyond the reach of children, so that unintentional thyroid poisoning can be avoided.