Evaluation of Autonomic Nervous System Dysfunction in Hypothyroid Children

Abstract

Background: This study explores autonomic nervous system (ANS) dysfunction in children with hypothyroidism, a condition known to disrupt metabolic and neurological regulation. While ANS abnormalities are well-documented in adults with hypothyroidism, pediatric data remain limited. Thyroid hormone deficiency may impair sympathetic and parasympathetic activity, detectable through heart rate variability (HRV) and cardiovascular reflex tests. Early identification of ANS dysfunction is crucial for timely intervention, as it can affect quality of life and development. Aim of the study: This study aims to assess autonomic function in children diagnosed with hypothyroidism systematically. Methods: This hospital-based, cross-sectional observational study was conducted over 15h months in the Physiology Departments of Prime Medical College and Hospital in Bangladesh. It included 100 children aged 5–16 years diagnosed with primary hypothyroidism, either newly or on levothyroxine ≤6 months. Using validated non-invasive methods, participants underwent thyroid and autonomic function testing (AFT). AFT included heart rate variability, deep breathing, Valsalva maneuver, orthostatic, handgrip, and cold pressor tests. Data were collected via structured questionnaires and laboratory evaluations. Statistical analysis was done using SPSS v26.0, with significance set at p<0.05 to assess correlations between TSH and autonomic parameters. Results: Among 100 children with primary hypothyroidism (mean age 10.8 ± 2.9 years; 59% female), most were from low or middle socioeconomic backgrounds. Thyroid profiles showed elevated TSH (14.7 ± 5.3 mIU/L) with reduced fT3 and fT4, and 34% had positive anti-TPO antibodies. Autonomic testing revealed reduced HRV (32.1 ± 10.4 ms), Valsalva, and E: I ratio, indicating parasympathetic dysfunction. Sympathetic responses were also altered. Overall, 28% had parasympathetic, 22% sympathetic, and 33% combined dysfunction; only 17% showed normal function. Significant negative correlations were observed between TSH levels and autonomic parameters, suggesting that increasing hypothyroidism severity is associated with greater autonomic dysfunction in affected children. Conclusion: Autonomic dysfunction is common in children with hypothyroidism, especially with elevated TSH levels, affecting both sympathetic and parasympathetic systems. Early screening for autonomic abnormalities may aid in detecting subclinical involvement and optimizing management, highlighting the need for a comprehensive approach in pediatric hypothyroid care.

Keywords: Hypothyroidism, Autonomic Nervous System, Thyroid Hormones and Autonomic Function Tests