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Levothyroxine dose in infancy may predict transient congenital hypothyroidism in children
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Infants prescribed a lower dose of levothyroxine therapy for congenital hypothyroidism with a eutopic thyroid gland are more likely to have a transient version of the disease vs. infants prescribed a higher dose of the therapy, according to findings published in Thyroid.
“Thorough evaluation of patients with congenital hypothyroidism with a eutopic gland, with the identification of explanatory factors, allows earlier ability to possibly distinguish between permanent versus transient congenital hypothyroidism,” Carole M. Saba, MD, of Assistance Publique-Hopitaux de Paris, told Endocrine Today. “The evaluation of levothyroxine dose requirements early, at age 6 months, particularly in patients with no family history of congenital hypothyroidism, allows early identification of patients for whom treatment should be stopped.”
Saba and colleagues analyzed data from 92 patients identified through a systematic neonatal screening for congenital hypothyroidism in the northern region of Paris between 2002 and 2012 who had a normally located gland, were treated with levothyroxine therapy during the neonatal period and aged at least 3 years at the time of the study. The median age of the patients was 19 days at treatment initiation, with median thyroid-stimulating hormone and free thyroxine concentrations of 69 mIU/L and 12.8 pmol/L, respectively. Median initial levothyroxine dose of levothyroxine was 8.4 µg/k per day. During follow-up, researchers classified patients as having either transient (serum TSH concentration < 7 mIU/L at least 4 weeks after levothyroxine stopped) or permanent congenital hypothyroidism. Researchers used multiple logistic regression analysis to investigate the association between outcome group (permanent vs. transient) and other clinical variables, including sex, prematurity, small for gestational age, neonatal problems and familial history of congenital hypothyroidism.
Within the cohort, 49 patients (54%) initially treated for congenital hypothyroidism during the neonatal period had a transient form of the disease. In these patients, levothyroxine was discontinued at a median age of 1.5 years. Patients with a transient form of the disease were more likely to have smaller increases in serum TSH concentrations at diagnosis, to start levothyroxine therapy later during the first month of life and receive lower doses of levothyroxine initially and at age 6 and 12 months.
In logistic regression analyses, researchers found that both family history of the disease and levothyroxine dose at age 6 months were the strongest predictors of the course of the disease, with patients with transient congenital hypothyroidism less likely to have a familial form of the disease and tending to have lower levothyroxine doses at age 6 months vs. those with permanent congenital hypothyroidism (P < .03).
Sex, being born small for gestational age, neonatal problems, iodine overload, congenital hypothyroidism severity as assessed by serum TSH and free T4 levels or bone maturation delay at diagnosis were not associated with the course of the disease, according to researchers.
“These original findings for patients with [congenital hypothyroidism] and an eutopic gland have important clinical implications for long-term patient management and highlight the need for appropriate and vigilant clinical and biological monitoring to prevent unnecessary long-term treatment during childhood,” the researchers wrote. “They highlight the need to evaluate [levothyroxine] dose requirements in patients as young as 6 months old, particularly for those with no familial history of [congenital hypothyroidism].”
The researchers noted that parents should be made aware when they are informed of their child’s diagnosis during the neonatal period that subsequent investigation will be necessary to determine whether the disease is persistent during childhood. – by Regina Schaffer
For more information:
Carole M. Saba, MD, can be reached at Saint George Hospital Medical University Center, clinic 205 Aschrafieh, Beirut, Lebanon; email: carole.saba@gmail.com.
Disclosures: The authors report no relevant financial disclosures.
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