Effects of low-dose levothyroxine on atrial natriuretic peptide and c-type natriuretic peptide in children with neonatal hypothyroidism.

Objective: This study was designed to explore the effects of low-dose levothyroxine (LT4) on levels of atrial natriuretic peptide (ANP) and c-type natriuretic peptide (CNP) in neonates with hypothyroidism (NH).

Methods: In this retrospective study, a total of 90 cases of NH screened out and confirmed by the First Affiliated Hospital of Zhejiang Chinese Medical University from October 2014 to February 2018 were selected as a study group. 80 healthy children who underwent physical examination during the same time period were enrolled as controls. Before and after treatment with LT4, the changes in the levels of serum thyroid stimulating hormone (TSH) and free thyroxine (FT) were observed, and the changes in the levels of ANP and CNP and their relationships to clinical efficacy were evaluated. Additionally, the growth and development of body and the scores of the China-Wechsler Younger Children Scale of Intelligence (C-WYCSI) were compared before and after the treatment, and the changes in the cardiac functions of children in the study group were evaluated. Independent risk factors for mental abnormality after treatment were analyzed by logistic regression.

Results: After treatment, TSH levels in patients declined, while the levels of T, T, free triiodothyronine (FT), and FT increased, without significant differences between groups. After treatment, ANP levels in patients increased but CNP levels decreased. ANP levels were negatively correlated with clinical efficacy, but CNP levels were positively correlated with it. Ultrasonic cardiography showed the improved cardiac functions. After treatment, the growth and development of body and the C-WYCSI scores increased compared to those before treatment. First visit date, T, FT, TSH were independent risk factors for mental disorders in children.

Conclusion: For children with NH, low-dose LT4 can correct the level of thyroid function, promote physical and mental development, and improve the levels of ANP and CNP.