Levothyroxine Use in Infants and Children with Congenital or Acquired Hypothyroidism

Contributing Editor: Marcia L. Buck, Pharm.D.; Editorial Board: Kristi N. Hofer, Pharm.D.; Michelle W. McCarthy, Pharm.D.


Pediatr Pharm. 2008;14(10) 

In This Article

Adverse Effects

The predominant adverse effects with levothyroxine are signs of hyperthyroidism, including fatigue, palpitations, tachycardia, hypertension, fever, headache, anxiety, irritability, insomnia, flushing, vomiting, abdominal cramps, diarrhea, muscle weakness, tremors, difficulty breathing, heat intolerance, and diaphoresis. Hair loss may occur, but is usually transient.[2,3]

Long-term exposure to elevated T4 levels may produce cardiac failure, elevated liver function tests, irregular menses, impaired fertility, weight loss, and decreased bone mineral density. In children receiving long-term therapy, there is a risk for impaired growth. Recent studies, however, have shown minimal impact of levothyroxine on growth. Lomenick and colleagues conducted a retrospective study of 68 children (mean age 10.8±3.2 years) with acquired hypothyroidism. Approximately a third of the children had lost weight (mean 2.3 kg) by their second visit; but by their last visit at 2-4 years, there was no significant change in their weight or body mass index (BMI) percentile.[2,3]

Rare serious reactions with levothyroxine include seizures, pseudotumor cerebri, slipped capital femoral epiphysis, craniosynostosis in infants, and premature epiphyseal closure. Hypersensitivity reactions have been reported to the inactive ingredients in levothyroxine products. Symptoms have included urticaria, angioedema, fever, gastrointestinal symptoms, arthralgia, serum sickness, and wheezing.[2,3]


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as: