Levothyroxine Dose at Discontinuation Linked to Congenital Hypothyroidism Permanence

The majority of infants with congenital hypothyroidism have transient disease and are able to successfully discontinue levothyroxine treatment, according to study results published in BMC Pediatrics. Patients receiving lower doses of levothyroxine were found to have greater success in discontinuing therapy and may benefit from early discontinuation.

Researchers conducted a retrospective chart review of infants diagnosed with congenital hypothyroidism between July 2005 and July 2015 (N=80). The researchers excluded patients who had aplastic, hypoplastic, or ectopic glands on thyroid ultrasonography or scan.

The primary outcome was predictive factors of transient disease in infants with congenital hypothyroidism. The researchers also examined results in infants who underwent a trial of early discontinuation, defined as discontinued levothyroxine before age 30 months.

Of all included patients, 63.8% (n=51) were born preterm. Levothyroxine discontinuation failed in 11.3% of patients (n=9) who were diagnosed with permanent congenital hypothyroidism. Compared with patients with transient congenital hypothyroidism, patients with permanent disease were on a higher levothyroxine dose at discontinuation (4.3 vs 2.9 μg/kg; P <.001).

The researchers did not find a difference in the percentage of permanent congenital hypothyroidism cases in preterm vs full-term patients.

In preterm patients, patients with permanent congenital hypothyroidism needed higher levothyroxine doses at discontinuation compared with patients with transient congenital hypothyroidism (3.8 vs 2.5 μg/kg; P =.018).

The researchers also plotted a receiver operating characteristic curve of thresholds of levothyroxine as predictors of transient disease. They concluded that discontinuation of levothyroxine at a dose of 2.86 μg/kg could suggest discontinuation failure (ie, permanent congenital hypothyroidism) with a sensitivity of 88.9% and specificity of 71.0%.

With regard to the outcomes of patients who underwent a trial of early discontinuation (n=9), levothyroxine was successfully discontinued in 8.

“[O]ur study [provides] useful data that support a trial of early discontinuation with low levothyroxine requirement, in both preterm and term infants,” the researchers wrote.

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Reference

Park ES, Yoon JY. Factors associated with permanent hypothyroidism in infants with congenital hypothyroidism. BMC Pediatr. 2019;19:453.