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Childhood hyperthyroidism may be on the rise
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Incidence of childhood hyperthyroidism in France, although rare, may be on the rise, peaking during adolescence and affecting girls more than boys, according to findings published in The Journal of Clinical Endocrinology and Metabolism.
“This population-based study provides new epidemiological data for hyperthyroidism in children and adolescents and the first estimates of its incidence in France, with robust results,” Joëlle Le Moal, PhD, an epidemiologist with French Public Health, Environmental Health Direction, Paris, and colleagues wrote. “It provides updated results and original data for incidence by age and sex, highlighting the increase in incidence and sex ratio in teenagers.”
Le Moal and colleagues analyzed data from all cases of hyperthyroidism in children aged 6 months to 17 years in France in 2015 identified from the French National Health Insurance Information System. To exclude cases of resuming treatment after relapse, researchers defined incident cases of hyperthyroidism as the first reimbursement for antithyroid drugs in 2015 recorded in the database, with no reimbursement for such drugs in the preceding 2 years. Additionally, researchers identified autoimmune diseases associated with hyperthyroidism, including cases of type 1 diabetes, Turner syndrome, Down syndrome, celiac disease and Addison’s disease. Researchers calculated sex ratio for the total population and by age group and explored month-to-month variations to detect a possible seasonal influence on the disease; they used a nonlinear Poisson model and spatial distribution of cases to estimate national incidence rate of childhood hyperthyroidism.
Within a cohort of 14.8 million children, researchers identified 670 children newly treated for hyperthyroidism in 2015, including 157 boys (23.4%) and 513 girls (76.6%). Principal antithyroid drugs used to treat hyperthyroidism in children in 2015 were carbimazole (63% of cases), thiamazole (31% of cases), propylthiouracil (5% of cases) and benzylthiouracil (1% of cases). Most patients used one drug during the observation period.
The overall incidence rate for childhood hyperthyroidism in 2015 was 4.58 per 100,000 person-years (95% CI, 3-6.99); however, the rate was 3.4 times higher in girls (incidence rate = 7.08; 95% CI, 4.85-10.3) vs. boys (incidence rate = 2.07; 95% CI, 1.03-4.16). Children aged 15 years and younger had a markedly lower incidence rate of 2.91 per 100,000 person-years (95% CI, 2.05-4.13); however, the rate was 2.4 times higher among girls than boys in this age group.
The higher incidence rate of hyperthyroidism among girls persisted throughout childhood. Girls aged 10 to 14 years had an incidence rate 3.2 times higher than boys, whereas girls aged 15 to 17 years had an incidence rate 5.7 times higher than boys, according to researchers.
“The [incidence rate] in girls was markedly higher than that in boys, and this difference increased strongly with age, particularly during the teenage years,” the researchers wrote. “The results of this study also extend our knowledge of the incidence of this disease in very young children, because about 10% of the patients in this cohort began receiving treatment before the age of 5 years.”
Among children with hyperthyroidism, 20 patients (3%) had associated autoimmune or genetic disease, with the most frequent being type 1 diabetes and Down syndrome.
The researchers noted that the French incidence rates are slightly higher than expected from the results published for earlier studies in northern European countries, and further studies are required to determine whether incidence is increasing in France.
“If such an increase is confirmed, it will be interesting to see whether it also concerns the youngest children, as shown over the last decade, for other autoimmune diseases, such as type 1 diabetes,” the researchers wrote. “The association of hyperthyroidism with other autoimmune conditions and hypotheses concerning links to environmental factors should be investigated over a longer study period.” – by Regina Schaffer
Disclosure: The authors report no relevant financial disclosures.
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