Levothyroxine overdose in an adult

Abstract

We describe a patient who overdosed thyroid hormone to attempt suicide. A 26-year-old woman ingested an aggregate of 3.5mg (70 tablets) of levothyroxine. Gastric lavage followed by activated charcoal and a laxative was done in an ER and the patient was admitted to intensive care unit. She remained asymptomatic except for slight fever and discharged from the hospital on the fourth day. Thyroid function studies were repeated on follow-up until the 19th day after ingestion. The thyroid hormone values on admission were T₄ 39.8μg·dl^-1 (normal range; 5.1-13.5), T₃ 175ng·dl^-1 (85-200) and TSH 5.03μU·ml^-1 (0.27-4.2). The values of serum T₃ and T₄ fell down temporary less than normal on the 4th day and then spouted up over normal range on the 7th day. Thyroid hormone values were normalized on the 19th day. Serious toxicity is uncommon after levothyroxine ingestion, but the onset of symptoms may be delayed because of long half-life and bioactivity of a metabolyte (T₃). Close observation is necessary for a couple of weeks. Non-specific, supportive therapy is more beneficial than antithyroidal therapy because overdosed levothyroxine, as a result of homeostasis mechanism, suppresses thyroid gland and therefore aggressive antithyroidal therapy may cause critical overdepression.